treewide: remove meaningless assignments in Makefiles

Message ID	20240221134201.2656908-1-masahiroy@kernel.org (mailing list archive)
State	New, archived
Headers	show Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 6931678B4A; Wed, 21 Feb 2024 13:42:08 +0000 (UTC) From: Masahiro Yamada <masahiroy@kernel.org> To: Peter Zijlstra <peterz@infradead.org>, Ingo Molnar <mingo@redhat.com>, Arnaldo Carvalho de Melo <acme@kernel.org>, Namhyung Kim <namhyung@kernel.org>, linux-perf-users@vger.kernel.org Cc: linux-kbuild@vger.kernel.org, linux-kernel@vger.kernel.org, Mark Rutland <mark.rutland@arm.com>, Alexander Shishkin <alexander.shishkin@linux.intel.com>, Jiri Olsa <jolsa@kernel.org>, Ian Rogers <irogers@google.com>, Adrian Hunter <adrian.hunter@intel.com>, Masahiro Yamada <masahiroy@kernel.org> Subject: [PATCH] treewide: remove meaningless assignments in Makefiles Date: Wed, 21 Feb 2024 22:42:01 +0900 Message-Id: <20240221134201.2656908-1-masahiroy@kernel.org> Precedence: bulk MIME-Version: 1.0 Content-Transfer-Encoding: 8bit
Series	treewide: remove meaningless assignments in Makefiles \| expand treewide: remove meaningless assignments in Makefiles

Masahiro Yamada Feb. 21, 2024, 1:42 p.m. UTC

In Makefiles, $(error ), $(warning ), and $(info ) expand to the empty
string, as explained in the GNU Make manual [1]:
 "The result of the expansion of this function is the empty string."

Therefore, they are no-op except for logging purposes.

$(shell ...) expands to the output of the command. It expands to the
empty string when the command does not print anything to stdout.
Hence, $(shell mkdir ...) is no-op except for creating the directory.

Remove meaningless assignments.

[1]: https://www.gnu.org/software/make/manual/make.html#Make-Control-Functions

Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
---

This is a treewide cleanup, but in practice, this is touching mostly
perf Makefiles. I am sending this to perf subsystem.


 tools/perf/Makefile.config           | 90 ++++++++++++++--------------
 tools/perf/Makefile.perf             |  4 +-
 tools/perf/arch/arm64/Makefile       |  2 +-
 tools/perf/arch/loongarch/Makefile   |  2 +-
 tools/perf/arch/mips/Makefile        |  2 +-
 tools/perf/arch/powerpc/Makefile     |  2 +-
 tools/perf/arch/s390/Makefile        |  2 +-
 tools/perf/arch/x86/Makefile         |  2 +-
 tools/scripts/Makefile.include       |  2 +-
 tools/testing/selftests/kvm/Makefile |  4 +-
 10 files changed, 56 insertions(+), 56 deletions(-)

Ian Rogers Feb. 21, 2024, 2:39 p.m. UTC | #1

On Wed, Feb 21, 2024 at 5:42 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> In Makefiles, $(error ), $(warning ), and $(info ) expand to the empty
> string, as explained in the GNU Make manual [1]:
>  "The result of the expansion of this function is the empty string."
>
> Therefore, they are no-op except for logging purposes.
>
> $(shell ...) expands to the output of the command. It expands to the
> empty string when the command does not print anything to stdout.
> Hence, $(shell mkdir ...) is no-op except for creating the directory.
>
> Remove meaningless assignments.
>
> [1]: https://www.gnu.org/software/make/manual/make.html#Make-Control-Functions
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

I can see why it was done, but I can also see the manual saying it is
unnecessary. The assignments also get cargo culted around, so removing
them should stop this.

Reviewed-by: Ian Rogers <irogers@google.com>

Thanks,
Ian

> ---
>
> This is a treewide cleanup, but in practice, this is touching mostly
> perf Makefiles. I am sending this to perf subsystem.
>
>
>  tools/perf/Makefile.config           | 90 ++++++++++++++--------------
>  tools/perf/Makefile.perf             |  4 +-
>  tools/perf/arch/arm64/Makefile       |  2 +-
>  tools/perf/arch/loongarch/Makefile   |  2 +-
>  tools/perf/arch/mips/Makefile        |  2 +-
>  tools/perf/arch/powerpc/Makefile     |  2 +-
>  tools/perf/arch/s390/Makefile        |  2 +-
>  tools/perf/arch/x86/Makefile         |  2 +-
>  tools/scripts/Makefile.include       |  2 +-
>  tools/testing/selftests/kvm/Makefile |  4 +-
>  10 files changed, 56 insertions(+), 56 deletions(-)
>
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index aa55850fbc21..6edf9916d41c 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -209,11 +209,11 @@ endif
>  include $(srctree)/tools/scripts/utilities.mak
>
>  ifeq ($(call get-executable,$(FLEX)),)
> -  dummy := $(error Error: $(FLEX) is missing on this system, please install it)
> +  $(error Error: $(FLEX) is missing on this system, please install it)
>  endif
>
>  ifeq ($(call get-executable,$(BISON)),)
> -  dummy := $(error Error: $(BISON) is missing on this system, please install it)
> +  $(error Error: $(BISON) is missing on this system, please install it)
>  endif
>
>  ifneq ($(OUTPUT),)
> @@ -438,46 +438,46 @@ else
>        LIBC_SUPPORT := 1
>      endif
>      ifeq ($(LIBC_SUPPORT),1)
> -      msg := $(error ERROR: No libelf found. Disables 'probe' tool, jvmti and BPF support. Please install libelf-dev, libelf-devel, elfutils-libelf-devel or build with NO_LIBELF=1.)
> +      $(error ERROR: No libelf found. Disables 'probe' tool, jvmti and BPF support. Please install libelf-dev, libelf-devel, elfutils-libelf-devel or build with NO_LIBELF=1.)
>      else
>        ifneq ($(filter s% -fsanitize=address%,$(EXTRA_CFLAGS),),)
>          ifneq ($(shell ldconfig -p | grep libasan >/dev/null 2>&1; echo $$?), 0)
> -          msg := $(error No libasan found, please install libasan);
> +          $(error No libasan found, please install libasan)
>          endif
>        endif
>
>        ifneq ($(filter s% -fsanitize=undefined%,$(EXTRA_CFLAGS),),)
>          ifneq ($(shell ldconfig -p | grep libubsan >/dev/null 2>&1; echo $$?), 0)
> -          msg := $(error No libubsan found, please install libubsan);
> +          $(error No libubsan found, please install libubsan)
>          endif
>        endif
>
>        ifneq ($(filter s% -static%,$(LDFLAGS),),)
> -        msg := $(error No static glibc found, please install glibc-static);
> +        $(error No static glibc found, please install glibc-static)
>        else
> -        msg := $(error No gnu/libc-version.h found, please install glibc-dev[el]);
> +        $(error No gnu/libc-version.h found, please install glibc-dev[el])
>        endif
>      endif
>    else
>      ifndef NO_LIBDW_DWARF_UNWIND
>        ifneq ($(feature-libdw-dwarf-unwind),1)
>          NO_LIBDW_DWARF_UNWIND := 1
> -        msg := $(warning No libdw DWARF unwind found, Please install elfutils-devel/libdw-dev >= 0.158 and/or set LIBDW_DIR);
> +        $(warning No libdw DWARF unwind found, Please install elfutils-devel/libdw-dev >= 0.158 and/or set LIBDW_DIR)
>        endif
>      endif
>      ifneq ($(feature-dwarf), 1)
>        ifndef NO_DWARF
> -        msg := $(warning No libdw.h found or old libdw.h found or elfutils is older than 0.138, disables dwarf support. Please install new elfutils-devel/libdw-dev);
> +        $(warning No libdw.h found or old libdw.h found or elfutils is older than 0.138, disables dwarf support. Please install new elfutils-devel/libdw-dev)
>          NO_DWARF := 1
>        endif
>      else
>        ifneq ($(feature-dwarf_getlocations), 1)
> -        msg := $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.157);
> +        $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.157)
>        else
>          CFLAGS += -DHAVE_DWARF_GETLOCATIONS_SUPPORT
>        endif # dwarf_getlocations
>        ifneq ($(feature-dwarf_getcfi), 1)
> -        msg := $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.142);
> +        $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.142)
>        else
>          CFLAGS += -DHAVE_DWARF_CFI_SUPPORT
>        endif # dwarf_getcfi
> @@ -525,7 +525,7 @@ ifdef CORESIGHT
>        endif
>      endif
>    else
> -    dummy := $(error Error: No libopencsd library found or the version is not up-to-date. Please install recent libopencsd to build with CORESIGHT=1)
> +    $(error Error: No libopencsd library found or the version is not up-to-date. Please install recent libopencsd to build with CORESIGHT=1)
>    endif
>  endif
>
> @@ -551,7 +551,7 @@ ifndef NO_LIBELF
>    ifeq ($(feature-libelf-gelf_getnote), 1)
>      CFLAGS += -DHAVE_GELF_GETNOTE_SUPPORT
>    else
> -    msg := $(warning gelf_getnote() not found on libelf, SDT support disabled);
> +    $(warning gelf_getnote() not found on libelf, SDT support disabled)
>    endif
>
>    ifeq ($(feature-libelf-getshdrstrndx), 1)
> @@ -568,7 +568,7 @@ ifndef NO_LIBELF
>
>    ifndef NO_DWARF
>      ifeq ($(origin PERF_HAVE_DWARF_REGS), undefined)
> -      msg := $(warning DWARF register mappings have not been defined for architecture $(SRCARCH), DWARF support disabled);
> +      $(warning DWARF register mappings have not been defined for architecture $(SRCARCH), DWARF support disabled)
>        NO_DWARF := 1
>      else
>        CFLAGS += -DHAVE_DWARF_SUPPORT $(LIBDW_CFLAGS)
> @@ -590,11 +590,11 @@ ifndef NO_LIBELF
>            $(call detected,CONFIG_LIBBPF)
>            $(call detected,CONFIG_LIBBPF_DYNAMIC)
>          else
> -          dummy := $(error Error: No libbpf devel library found or older than v1.0, please install/update libbpf-devel);
> +          $(error Error: No libbpf devel library found or older than v1.0, please install/update libbpf-devel)
>          endif
>        else
>          ifeq ($(NO_ZLIB), 1)
> -          dummy := $(warning Warning: Statically building libbpf not possible as zlib is missing)
> +          $(warning Warning: Statically building libbpf not possible as zlib is missing)
>            NO_LIBBPF := 1
>          else
>            # Libbpf will be built as a static library from tools/lib/bpf.
> @@ -609,7 +609,7 @@ endif # NO_LIBELF
>
>  ifndef NO_SDT
>    ifneq ($(feature-sdt), 1)
> -    msg := $(warning No sys/sdt.h found, no SDT events are defined, please install systemtap-sdt-devel or systemtap-sdt-dev);
> +    $(warning No sys/sdt.h found, no SDT events are defined, please install systemtap-sdt-devel or systemtap-sdt-dev)
>      NO_SDT := 1;
>    else
>      CFLAGS += -DHAVE_SDT_EVENT
> @@ -651,13 +651,13 @@ ifndef NO_LIBUNWIND
>      have_libunwind = 1
>      $(call feature_check,libunwind-debug-frame-aarch64)
>      ifneq ($(feature-libunwind-debug-frame-aarch64), 1)
> -      msg := $(warning No debug_frame support found in libunwind-aarch64);
> +      $(warning No debug_frame support found in libunwind-aarch64)
>        CFLAGS += -DNO_LIBUNWIND_DEBUG_FRAME_AARCH64
>      endif
>    endif
>
>    ifneq ($(feature-libunwind), 1)
> -    msg := $(warning No libunwind found. Please install libunwind-dev[el] >= 1.1 and/or set LIBUNWIND_DIR);
> +    $(warning No libunwind found. Please install libunwind-dev[el] >= 1.1 and/or set LIBUNWIND_DIR)
>      NO_LOCAL_LIBUNWIND := 1
>    else
>      have_libunwind := 1
> @@ -673,7 +673,7 @@ endif
>
>  ifndef NO_LIBBPF
>    ifneq ($(feature-bpf), 1)
> -    msg := $(warning BPF API too old. Please install recent kernel headers. BPF support in 'perf record' is disabled.)
> +    $(warning BPF API too old. Please install recent kernel headers. BPF support in 'perf record' is disabled.)
>      NO_LIBBPF := 1
>    endif
>  endif
> @@ -686,28 +686,28 @@ endif
>
>  ifeq ($(BUILD_BPF_SKEL),1)
>    ifeq ($(filter -DHAVE_LIBELF_SUPPORT, $(CFLAGS)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as libelf is required by bpftool)
> +    $(warning Warning: Disabled BPF skeletons as libelf is required by bpftool)
>      BUILD_BPF_SKEL := 0
>    else ifeq ($(filter -DHAVE_ZLIB_SUPPORT, $(CFLAGS)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as zlib is required by bpftool)
> +    $(warning Warning: Disabled BPF skeletons as zlib is required by bpftool)
>      BUILD_BPF_SKEL := 0
>    else ifeq ($(filter -DHAVE_LIBBPF_SUPPORT, $(CFLAGS)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as libbpf is required)
> +    $(warning Warning: Disabled BPF skeletons as libbpf is required)
>      BUILD_BPF_SKEL := 0
>    else ifeq ($(call get-executable,$(CLANG)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as clang ($(CLANG)) is missing)
> +    $(warning Warning: Disabled BPF skeletons as clang ($(CLANG)) is missing)
>      BUILD_BPF_SKEL := 0
>    else
>      CLANG_VERSION := $(shell $(CLANG) --version | head -1 | sed 's/.*clang version \([[:digit:]]\+.[[:digit:]]\+.[[:digit:]]\+\).*/\1/g')
>      ifeq ($(call version-lt3,$(CLANG_VERSION),12.0.1),1)
> -      dummy := $(warning Warning: Disabled BPF skeletons as reliable BTF generation needs at least $(CLANG) version 12.0.1)
> +      $(warning Warning: Disabled BPF skeletons as reliable BTF generation needs at least $(CLANG) version 12.0.1)
>        BUILD_BPF_SKEL := 0
>      endif
>    endif
>    ifeq ($(BUILD_BPF_SKEL),1)
>      $(call feature_check,clang-bpf-co-re)
>      ifeq ($(feature-clang-bpf-co-re), 0)
> -      dummy := $(warning Warning: Disabled BPF skeletons as clang is too old)
> +      $(warning Warning: Disabled BPF skeletons as clang is too old)
>        BUILD_BPF_SKEL := 0
>      endif
>    endif
> @@ -727,7 +727,7 @@ dwarf-post-unwind-text := BUG
>  # setup DWARF post unwinder
>  ifdef NO_LIBUNWIND
>    ifdef NO_LIBDW_DWARF_UNWIND
> -    msg := $(warning Disabling post unwind, no support found.);
> +    $(warning Disabling post unwind, no support found.)
>      dwarf-post-unwind := 0
>    else
>      dwarf-post-unwind-text := libdw
> @@ -753,7 +753,7 @@ ifndef NO_LOCAL_LIBUNWIND
>    ifeq ($(SRCARCH),$(filter $(SRCARCH),arm arm64))
>      $(call feature_check,libunwind-debug-frame)
>      ifneq ($(feature-libunwind-debug-frame), 1)
> -      msg := $(warning No debug_frame support found in libunwind);
> +      $(warning No debug_frame support found in libunwind)
>        CFLAGS += -DNO_LIBUNWIND_DEBUG_FRAME
>      endif
>    else
> @@ -782,7 +782,7 @@ ifneq ($(NO_LIBTRACEEVENT),1)
>      ifndef NO_LIBAUDIT
>        $(call feature_check,libaudit)
>        ifneq ($(feature-libaudit), 1)
> -        msg := $(warning No libaudit.h found, disables 'trace' tool, please install audit-libs-devel or libaudit-dev);
> +        $(warning No libaudit.h found, disables 'trace' tool, please install audit-libs-devel or libaudit-dev)
>          NO_LIBAUDIT := 1
>        else
>          CFLAGS += -DHAVE_LIBAUDIT_SUPPORT
> @@ -795,7 +795,7 @@ endif
>
>  ifndef NO_LIBCRYPTO
>    ifneq ($(feature-libcrypto), 1)
> -    msg := $(warning No libcrypto.h found, disables jitted code injection, please install openssl-devel or libssl-dev);
> +    $(warning No libcrypto.h found, disables jitted code injection, please install openssl-devel or libssl-dev)
>      NO_LIBCRYPTO := 1
>    else
>      CFLAGS += -DHAVE_LIBCRYPTO_SUPPORT
> @@ -807,7 +807,7 @@ endif
>  ifndef NO_SLANG
>    ifneq ($(feature-libslang), 1)
>      ifneq ($(feature-libslang-include-subdir), 1)
> -      msg := $(warning slang not found, disables TUI support. Please install slang-devel, libslang-dev or libslang2-dev);
> +      $(warning slang not found, disables TUI support. Please install slang-devel, libslang-dev or libslang2-dev)
>        NO_SLANG := 1
>      else
>        CFLAGS += -DHAVE_SLANG_INCLUDE_SUBDIR
> @@ -825,7 +825,7 @@ ifdef GTK2
>    FLAGS_GTK2=$(CFLAGS) $(LDFLAGS) $(EXTLIBS) $(shell $(PKG_CONFIG) --libs --cflags gtk+-2.0 2>/dev/null)
>    $(call feature_check,gtk2)
>    ifneq ($(feature-gtk2), 1)
> -    msg := $(warning GTK2 not found, disables GTK2 support. Please install gtk2-devel or libgtk2.0-dev);
> +    $(warning GTK2 not found, disables GTK2 support. Please install gtk2-devel or libgtk2.0-dev)
>      NO_GTK2 := 1
>    else
>      $(call feature_check,gtk2-infobar)
> @@ -854,7 +854,7 @@ else
>    ifneq ($(feature-libperl), 1)
>      CFLAGS += -DNO_LIBPERL
>      NO_LIBPERL := 1
> -    msg := $(warning Missing perl devel files. Disabling perl scripting support, please install perl-ExtUtils-Embed/libperl-dev);
> +    $(warning Missing perl devel files. Disabling perl scripting support, please install perl-ExtUtils-Embed/libperl-dev)
>    else
>      LDFLAGS += $(PERL_EMBED_LDFLAGS)
>      EXTLIBS += $(PERL_EMBED_LIBADD)
> @@ -869,7 +869,7 @@ endif
>  ifeq ($(feature-timerfd), 1)
>    CFLAGS += -DHAVE_TIMERFD_SUPPORT
>  else
> -  msg := $(warning No timerfd support. Disables 'perf kvm stat live');
> +  $(warning No timerfd support. Disables 'perf kvm stat live')
>  endif
>
>  disable-python = $(eval $(disable-python_code))
> @@ -903,7 +903,7 @@ else
>             PYTHON_EXTENSION_SUFFIX := $(shell $(PYTHON) -c 'from importlib import machinery; print(machinery.EXTENSION_SUFFIXES[0])')
>             LANG_BINDINGS += $(obj-perf)python/perf$(PYTHON_EXTENSION_SUFFIX)
>          else
> -           msg := $(warning Missing python setuptools, the python binding won't be built, please install python3-setuptools or equivalent);
> +           $(warning Missing python setuptools, the python binding won't be built, please install python3-setuptools or equivalent)
>           endif
>           CFLAGS += -DHAVE_LIBPYTHON_SUPPORT
>           $(call detected,CONFIG_LIBPYTHON)
> @@ -962,7 +962,7 @@ ifdef BUILD_NONDISTRO
>    ifeq ($(feature-libbfd-buildid), 1)
>      CFLAGS += -DHAVE_LIBBFD_BUILDID_SUPPORT
>    else
> -    msg := $(warning Old version of libbfd/binutils things like PE executable profiling will not be available);
> +    $(warning Old version of libbfd/binutils things like PE executable profiling will not be available)
>    endif
>  endif
>
> @@ -994,7 +994,7 @@ ifndef NO_LZMA
>      EXTLIBS += -llzma
>      $(call detected,CONFIG_LZMA)
>    else
> -    msg := $(warning No liblzma found, disables xz kernel module decompression, please install xz-devel/liblzma-dev);
> +    $(warning No liblzma found, disables xz kernel module decompression, please install xz-devel/liblzma-dev)
>      NO_LZMA := 1
>    endif
>  endif
> @@ -1007,7 +1007,7 @@ ifndef NO_LIBZSTD
>      EXTLIBS += -lzstd
>      $(call detected,CONFIG_ZSTD)
>    else
> -    msg := $(warning No libzstd found, disables trace compression, please install libzstd-dev[el] and/or set LIBZSTD_DIR);
> +    $(warning No libzstd found, disables trace compression, please install libzstd-dev[el] and/or set LIBZSTD_DIR)
>      NO_LIBZSTD := 1
>    endif
>  endif
> @@ -1018,7 +1018,7 @@ ifndef NO_LIBCAP
>      EXTLIBS += -lcap
>      $(call detected,CONFIG_LIBCAP)
>    else
> -    msg := $(warning No libcap found, disables capability support, please install libcap-devel/libcap-dev);
> +    $(warning No libcap found, disables capability support, please install libcap-devel/libcap-dev)
>      NO_LIBCAP := 1
>    endif
>  endif
> @@ -1031,11 +1031,11 @@ endif
>
>  ifndef NO_LIBNUMA
>    ifeq ($(feature-libnuma), 0)
> -    msg := $(warning No numa.h found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev);
> +    $(warning No numa.h found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev)
>      NO_LIBNUMA := 1
>    else
>      ifeq ($(feature-numa_num_possible_cpus), 0)
> -      msg := $(warning Old numa library found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev >= 2.0.8);
> +      $(warning Old numa library found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev >= 2.0.8)
>        NO_LIBNUMA := 1
>      else
>        CFLAGS += -DHAVE_LIBNUMA_SUPPORT
> @@ -1090,14 +1090,14 @@ ifndef NO_LIBBABELTRACE
>      EXTLIBS += -lbabeltrace-ctf
>      $(call detected,CONFIG_LIBBABELTRACE)
>    else
> -    msg := $(warning No libbabeltrace found, disables 'perf data' CTF format support, please install libbabeltrace-dev[el]/libbabeltrace-ctf-dev);
> +    $(warning No libbabeltrace found, disables 'perf data' CTF format support, please install libbabeltrace-dev[el]/libbabeltrace-ctf-dev)
>    endif
>  endif
>
>  ifndef NO_AUXTRACE
>    ifeq ($(SRCARCH),x86)
>      ifeq ($(feature-get_cpuid), 0)
> -      msg := $(warning Your gcc lacks the __get_cpuid() builtin, disables support for auxtrace/Intel PT, please install a newer gcc);
> +      $(warning Your gcc lacks the __get_cpuid() builtin, disables support for auxtrace/Intel PT, please install a newer gcc)
>        NO_AUXTRACE := 1
>      endif
>    endif
> @@ -1155,7 +1155,7 @@ ifndef NO_LIBPFM4
>      ASCIIDOC_EXTRA = -aHAVE_LIBPFM=1
>      $(call detected,CONFIG_LIBPFM4)
>    else
> -    msg := $(warning libpfm4 not found, disables libpfm4 support. Please install libpfm4-dev);
> +    $(warning libpfm4 not found, disables libpfm4 support. Please install libpfm4-dev)
>    endif
>  endif
>
> @@ -1173,7 +1173,7 @@ ifneq ($(NO_LIBTRACEEVENT),1)
>      CFLAGS += -DLIBTRACEEVENT_VERSION=$(LIBTRACEEVENT_VERSION_CPP)
>      $(call detected,CONFIG_LIBTRACEEVENT)
>    else
> -    dummy := $(error ERROR: libtraceevent is missing. Please install libtraceevent-dev/libtraceevent-devel or build with NO_LIBTRACEEVENT=1)
> +    $(error ERROR: libtraceevent is missing. Please install libtraceevent-dev/libtraceevent-devel or build with NO_LIBTRACEEVENT=1)
>    endif
>
>    $(call feature_check,libtracefs)
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index f8774a9b1377..3707fed8dfde 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -482,7 +482,7 @@ drm_hdr_dir := $(srctree)/tools/include/uapi/drm
>  drm_ioctl_tbl := $(srctree)/tools/perf/trace/beauty/drm_ioctl.sh
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(beauty_ioctl_outdir)' ] || mkdir -p '$(beauty_ioctl_outdir)')
> +$(shell [ -d '$(beauty_ioctl_outdir)' ] || mkdir -p '$(beauty_ioctl_outdir)')
>
>  $(drm_ioctl_array): $(drm_hdr_dir)/drm.h $(drm_hdr_dir)/i915_drm.h $(drm_ioctl_tbl)
>         $(Q)$(SHELL) '$(drm_ioctl_tbl)' $(drm_hdr_dir) > $@
> @@ -672,7 +672,7 @@ tests-coresight-targets-clean:
>  all: shell_compatibility_test $(ALL_PROGRAMS) $(LANG_BINDINGS) $(OTHER_PROGRAMS) tests-coresight-targets
>
>  # Create python binding output directory if not already present
> -_dummy := $(shell [ -d '$(OUTPUT)python' ] || mkdir -p '$(OUTPUT)python')
> +$(shell [ -d '$(OUTPUT)python' ] || mkdir -p '$(OUTPUT)python')
>
>  $(OUTPUT)python/perf$(PYTHON_EXTENSION_SUFFIX): $(PYTHON_EXT_SRCS) $(PYTHON_EXT_DEPS) $(LIBPERF) $(LIBSUBCMD)
>         $(QUIET_GEN)LDSHARED="$(CC) -pthread -shared" \
> diff --git a/tools/perf/arch/arm64/Makefile b/tools/perf/arch/arm64/Makefile
> index fab3095fb5d0..5735ed4479bb 100644
> --- a/tools/perf/arch/arm64/Makefile
> +++ b/tools/perf/arch/arm64/Makefile
> @@ -18,7 +18,7 @@ sysprf := $(srctree)/tools/perf/arch/arm64/entry/syscalls/
>  systbl := $(sysprf)/mksyscalltbl
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>
>  $(header): $(sysdef) $(systbl)
>         $(Q)$(SHELL) '$(systbl)' '$(CC)' '$(HOSTCC)' $(incpath) $(sysdef) > $@
> diff --git a/tools/perf/arch/loongarch/Makefile b/tools/perf/arch/loongarch/Makefile
> index c392e7af4743..3992a67a87d9 100644
> --- a/tools/perf/arch/loongarch/Makefile
> +++ b/tools/perf/arch/loongarch/Makefile
> @@ -17,7 +17,7 @@ sysprf := $(srctree)/tools/perf/arch/loongarch/entry/syscalls/
>  systbl := $(sysprf)/mksyscalltbl
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>
>  $(header): $(sysdef) $(systbl)
>         $(Q)$(SHELL) '$(systbl)' '$(CC)' '$(HOSTCC)' $(incpath) $(sysdef) > $@
> diff --git a/tools/perf/arch/mips/Makefile b/tools/perf/arch/mips/Makefile
> index 8bc09072e3d6..cd0b011b3be5 100644
> --- a/tools/perf/arch/mips/Makefile
> +++ b/tools/perf/arch/mips/Makefile
> @@ -11,7 +11,7 @@ sysdef := $(sysprf)/syscall_n64.tbl
>  systbl := $(sysprf)/mksyscalltbl
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>
>  $(header): $(sysdef) $(systbl)
>         $(Q)$(SHELL) '$(systbl)' $(sysdef) > $@
> diff --git a/tools/perf/arch/powerpc/Makefile b/tools/perf/arch/powerpc/Makefile
> index 840ea0e59287..bf6d323574f6 100644
> --- a/tools/perf/arch/powerpc/Makefile
> +++ b/tools/perf/arch/powerpc/Makefile
> @@ -19,7 +19,7 @@ sysdef := $(sysprf)/syscall.tbl
>  systbl := $(sysprf)/mksyscalltbl
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>
>  $(header64): $(sysdef) $(systbl)
>         $(Q)$(SHELL) '$(systbl)' '64' $(sysdef) > $@
> diff --git a/tools/perf/arch/s390/Makefile b/tools/perf/arch/s390/Makefile
> index 74bffbea03e2..56994e63b43a 100644
> --- a/tools/perf/arch/s390/Makefile
> +++ b/tools/perf/arch/s390/Makefile
> @@ -17,7 +17,7 @@ sysdef := $(sysprf)/syscall.tbl
>  systbl := $(sysprf)/mksyscalltbl
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>
>  $(header): $(sysdef) $(systbl)
>         $(Q)$(SHELL) '$(systbl)' $(sysdef) > $@
> diff --git a/tools/perf/arch/x86/Makefile b/tools/perf/arch/x86/Makefile
> index 5a9f9a7bf07d..8952e00f9b60 100644
> --- a/tools/perf/arch/x86/Makefile
> +++ b/tools/perf/arch/x86/Makefile
> @@ -17,7 +17,7 @@ sys       := $(srctree)/tools/perf/arch/x86/entry/syscalls
>  systbl    := $(sys)/syscalltbl.sh
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>
>  $(header): $(sys)/syscall_64.tbl $(systbl)
>         $(Q)$(SHELL) '$(systbl)' $(sys)/syscall_64.tbl 'x86_64' > $@
> diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
> index 6fba29f3222d..0aa4005017c7 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
> @@ -1,7 +1,7 @@
>  # SPDX-License-Identifier: GPL-2.0
>  ifneq ($(O),)
>  ifeq ($(origin O), command line)
> -       dummy := $(if $(shell cd $(PWD); test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)
> +        $(if $(shell cd $(PWD); test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)
>         ABSOLUTE_O := $(shell cd $(PWD); cd $(O) ; pwd)
>         OUTPUT := $(ABSOLUTE_O)/$(if $(subdir),$(subdir)/)
>         COMMAND_O := O=$(ABSOLUTE_O)
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 492e937fab00..14684aeb4b55 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -285,7 +285,7 @@ EXTRA_CLEAN += $(GEN_HDRS) \
>                $(TEST_GEN_OBJ) \
>                cscope.*
>
> -x := $(shell mkdir -p $(sort $(dir $(LIBKVM_C_OBJ) $(LIBKVM_S_OBJ))))
> +$(shell mkdir -p $(sort $(dir $(LIBKVM_C_OBJ) $(LIBKVM_S_OBJ))))
>  $(LIBKVM_C_OBJ): $(OUTPUT)/%.o: %.c $(GEN_HDRS)
>         $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c $< -o $@
>
> @@ -298,7 +298,7 @@ $(LIBKVM_S_OBJ): $(OUTPUT)/%.o: %.S $(GEN_HDRS)
>  $(LIBKVM_STRING_OBJ): $(OUTPUT)/%.o: %.c
>         $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c -ffreestanding $< -o $@
>
> -x := $(shell mkdir -p $(sort $(dir $(TEST_GEN_PROGS))))
> +$(shell mkdir -p $(sort $(dir $(TEST_GEN_PROGS))))
>  $(SPLIT_TESTS_OBJS): $(GEN_HDRS)
>  $(TEST_GEN_PROGS): $(LIBKVM_OBJS)
>  $(TEST_GEN_PROGS_EXTENDED): $(LIBKVM_OBJS)
> --
> 2.40.1
>

Arnaldo Carvalho de Melo Feb. 21, 2024, 5:08 p.m. UTC | #2

On Wed, Feb 21, 2024 at 10:42:01PM +0900, Masahiro Yamada wrote:
> In Makefiles, $(error ), $(warning ), and $(info ) expand to the empty
> string, as explained in the GNU Make manual [1]:
>  "The result of the expansion of this function is the empty string."
> 
> Therefore, they are no-op except for logging purposes.
> 
> $(shell ...) expands to the output of the command. It expands to the
> empty string when the command does not print anything to stdout.
> Hence, $(shell mkdir ...) is no-op except for creating the directory.
> 
> Remove meaningless assignments.
> 
> [1]: https://www.gnu.org/software/make/manual/make.html#Make-Control-Functions

Ok, some were already done without those assignments:

tools/perf/Makefile.config:    $(warning No alternatives command found, you need to set JDIR= to point to the root of your Java directory)
tools/perf/Makefile.config:    $(warning No openjdk development package found, please install JDK package, e.g. openjdk-8-jdk, java-1.8.0-openjdk-devel)

And the docs says its meaningless, and it makes the Makefiles more
compact, all good:

Reviewed-by: Arnaldo Carvalho de Melo <acme@redhat.com>

- Arnaldo
 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
> 
> This is a treewide cleanup, but in practice, this is touching mostly
> perf Makefiles. I am sending this to perf subsystem.
> 
> 
>  tools/perf/Makefile.config           | 90 ++++++++++++++--------------
>  tools/perf/Makefile.perf             |  4 +-
>  tools/perf/arch/arm64/Makefile       |  2 +-
>  tools/perf/arch/loongarch/Makefile   |  2 +-
>  tools/perf/arch/mips/Makefile        |  2 +-
>  tools/perf/arch/powerpc/Makefile     |  2 +-
>  tools/perf/arch/s390/Makefile        |  2 +-
>  tools/perf/arch/x86/Makefile         |  2 +-
>  tools/scripts/Makefile.include       |  2 +-
>  tools/testing/selftests/kvm/Makefile |  4 +-
>  10 files changed, 56 insertions(+), 56 deletions(-)
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index aa55850fbc21..6edf9916d41c 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -209,11 +209,11 @@ endif
>  include $(srctree)/tools/scripts/utilities.mak
>  
>  ifeq ($(call get-executable,$(FLEX)),)
> -  dummy := $(error Error: $(FLEX) is missing on this system, please install it)
> +  $(error Error: $(FLEX) is missing on this system, please install it)
>  endif
>  
>  ifeq ($(call get-executable,$(BISON)),)
> -  dummy := $(error Error: $(BISON) is missing on this system, please install it)
> +  $(error Error: $(BISON) is missing on this system, please install it)
>  endif
>  
>  ifneq ($(OUTPUT),)
> @@ -438,46 +438,46 @@ else
>        LIBC_SUPPORT := 1
>      endif
>      ifeq ($(LIBC_SUPPORT),1)
> -      msg := $(error ERROR: No libelf found. Disables 'probe' tool, jvmti and BPF support. Please install libelf-dev, libelf-devel, elfutils-libelf-devel or build with NO_LIBELF=1.)
> +      $(error ERROR: No libelf found. Disables 'probe' tool, jvmti and BPF support. Please install libelf-dev, libelf-devel, elfutils-libelf-devel or build with NO_LIBELF=1.)
>      else
>        ifneq ($(filter s% -fsanitize=address%,$(EXTRA_CFLAGS),),)
>          ifneq ($(shell ldconfig -p | grep libasan >/dev/null 2>&1; echo $$?), 0)
> -          msg := $(error No libasan found, please install libasan);
> +          $(error No libasan found, please install libasan)
>          endif
>        endif
>  
>        ifneq ($(filter s% -fsanitize=undefined%,$(EXTRA_CFLAGS),),)
>          ifneq ($(shell ldconfig -p | grep libubsan >/dev/null 2>&1; echo $$?), 0)
> -          msg := $(error No libubsan found, please install libubsan);
> +          $(error No libubsan found, please install libubsan)
>          endif
>        endif
>  
>        ifneq ($(filter s% -static%,$(LDFLAGS),),)
> -        msg := $(error No static glibc found, please install glibc-static);
> +        $(error No static glibc found, please install glibc-static)
>        else
> -        msg := $(error No gnu/libc-version.h found, please install glibc-dev[el]);
> +        $(error No gnu/libc-version.h found, please install glibc-dev[el])
>        endif
>      endif
>    else
>      ifndef NO_LIBDW_DWARF_UNWIND
>        ifneq ($(feature-libdw-dwarf-unwind),1)
>          NO_LIBDW_DWARF_UNWIND := 1
> -        msg := $(warning No libdw DWARF unwind found, Please install elfutils-devel/libdw-dev >= 0.158 and/or set LIBDW_DIR);
> +        $(warning No libdw DWARF unwind found, Please install elfutils-devel/libdw-dev >= 0.158 and/or set LIBDW_DIR)
>        endif
>      endif
>      ifneq ($(feature-dwarf), 1)
>        ifndef NO_DWARF
> -        msg := $(warning No libdw.h found or old libdw.h found or elfutils is older than 0.138, disables dwarf support. Please install new elfutils-devel/libdw-dev);
> +        $(warning No libdw.h found or old libdw.h found or elfutils is older than 0.138, disables dwarf support. Please install new elfutils-devel/libdw-dev)
>          NO_DWARF := 1
>        endif
>      else
>        ifneq ($(feature-dwarf_getlocations), 1)
> -        msg := $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.157);
> +        $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.157)
>        else
>          CFLAGS += -DHAVE_DWARF_GETLOCATIONS_SUPPORT
>        endif # dwarf_getlocations
>        ifneq ($(feature-dwarf_getcfi), 1)
> -        msg := $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.142);
> +        $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.142)
>        else
>          CFLAGS += -DHAVE_DWARF_CFI_SUPPORT
>        endif # dwarf_getcfi
> @@ -525,7 +525,7 @@ ifdef CORESIGHT
>        endif
>      endif
>    else
> -    dummy := $(error Error: No libopencsd library found or the version is not up-to-date. Please install recent libopencsd to build with CORESIGHT=1)
> +    $(error Error: No libopencsd library found or the version is not up-to-date. Please install recent libopencsd to build with CORESIGHT=1)
>    endif
>  endif
>  
> @@ -551,7 +551,7 @@ ifndef NO_LIBELF
>    ifeq ($(feature-libelf-gelf_getnote), 1)
>      CFLAGS += -DHAVE_GELF_GETNOTE_SUPPORT
>    else
> -    msg := $(warning gelf_getnote() not found on libelf, SDT support disabled);
> +    $(warning gelf_getnote() not found on libelf, SDT support disabled)
>    endif
>  
>    ifeq ($(feature-libelf-getshdrstrndx), 1)
> @@ -568,7 +568,7 @@ ifndef NO_LIBELF
>  
>    ifndef NO_DWARF
>      ifeq ($(origin PERF_HAVE_DWARF_REGS), undefined)
> -      msg := $(warning DWARF register mappings have not been defined for architecture $(SRCARCH), DWARF support disabled);
> +      $(warning DWARF register mappings have not been defined for architecture $(SRCARCH), DWARF support disabled)
>        NO_DWARF := 1
>      else
>        CFLAGS += -DHAVE_DWARF_SUPPORT $(LIBDW_CFLAGS)
> @@ -590,11 +590,11 @@ ifndef NO_LIBELF
>            $(call detected,CONFIG_LIBBPF)
>            $(call detected,CONFIG_LIBBPF_DYNAMIC)
>          else
> -          dummy := $(error Error: No libbpf devel library found or older than v1.0, please install/update libbpf-devel);
> +          $(error Error: No libbpf devel library found or older than v1.0, please install/update libbpf-devel)
>          endif
>        else
>          ifeq ($(NO_ZLIB), 1)
> -          dummy := $(warning Warning: Statically building libbpf not possible as zlib is missing)
> +          $(warning Warning: Statically building libbpf not possible as zlib is missing)
>            NO_LIBBPF := 1
>          else
>            # Libbpf will be built as a static library from tools/lib/bpf.
> @@ -609,7 +609,7 @@ endif # NO_LIBELF
>  
>  ifndef NO_SDT
>    ifneq ($(feature-sdt), 1)
> -    msg := $(warning No sys/sdt.h found, no SDT events are defined, please install systemtap-sdt-devel or systemtap-sdt-dev);
> +    $(warning No sys/sdt.h found, no SDT events are defined, please install systemtap-sdt-devel or systemtap-sdt-dev)
>      NO_SDT := 1;
>    else
>      CFLAGS += -DHAVE_SDT_EVENT
> @@ -651,13 +651,13 @@ ifndef NO_LIBUNWIND
>      have_libunwind = 1
>      $(call feature_check,libunwind-debug-frame-aarch64)
>      ifneq ($(feature-libunwind-debug-frame-aarch64), 1)
> -      msg := $(warning No debug_frame support found in libunwind-aarch64);
> +      $(warning No debug_frame support found in libunwind-aarch64)
>        CFLAGS += -DNO_LIBUNWIND_DEBUG_FRAME_AARCH64
>      endif
>    endif
>  
>    ifneq ($(feature-libunwind), 1)
> -    msg := $(warning No libunwind found. Please install libunwind-dev[el] >= 1.1 and/or set LIBUNWIND_DIR);
> +    $(warning No libunwind found. Please install libunwind-dev[el] >= 1.1 and/or set LIBUNWIND_DIR)
>      NO_LOCAL_LIBUNWIND := 1
>    else
>      have_libunwind := 1
> @@ -673,7 +673,7 @@ endif
>  
>  ifndef NO_LIBBPF
>    ifneq ($(feature-bpf), 1)
> -    msg := $(warning BPF API too old. Please install recent kernel headers. BPF support in 'perf record' is disabled.)
> +    $(warning BPF API too old. Please install recent kernel headers. BPF support in 'perf record' is disabled.)
>      NO_LIBBPF := 1
>    endif
>  endif
> @@ -686,28 +686,28 @@ endif
>  
>  ifeq ($(BUILD_BPF_SKEL),1)
>    ifeq ($(filter -DHAVE_LIBELF_SUPPORT, $(CFLAGS)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as libelf is required by bpftool)
> +    $(warning Warning: Disabled BPF skeletons as libelf is required by bpftool)
>      BUILD_BPF_SKEL := 0
>    else ifeq ($(filter -DHAVE_ZLIB_SUPPORT, $(CFLAGS)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as zlib is required by bpftool)
> +    $(warning Warning: Disabled BPF skeletons as zlib is required by bpftool)
>      BUILD_BPF_SKEL := 0
>    else ifeq ($(filter -DHAVE_LIBBPF_SUPPORT, $(CFLAGS)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as libbpf is required)
> +    $(warning Warning: Disabled BPF skeletons as libbpf is required)
>      BUILD_BPF_SKEL := 0
>    else ifeq ($(call get-executable,$(CLANG)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as clang ($(CLANG)) is missing)
> +    $(warning Warning: Disabled BPF skeletons as clang ($(CLANG)) is missing)
>      BUILD_BPF_SKEL := 0
>    else
>      CLANG_VERSION := $(shell $(CLANG) --version | head -1 | sed 's/.*clang version \([[:digit:]]\+.[[:digit:]]\+.[[:digit:]]\+\).*/\1/g')
>      ifeq ($(call version-lt3,$(CLANG_VERSION),12.0.1),1)
> -      dummy := $(warning Warning: Disabled BPF skeletons as reliable BTF generation needs at least $(CLANG) version 12.0.1)
> +      $(warning Warning: Disabled BPF skeletons as reliable BTF generation needs at least $(CLANG) version 12.0.1)
>        BUILD_BPF_SKEL := 0
>      endif
>    endif
>    ifeq ($(BUILD_BPF_SKEL),1)
>      $(call feature_check,clang-bpf-co-re)
>      ifeq ($(feature-clang-bpf-co-re), 0)
> -      dummy := $(warning Warning: Disabled BPF skeletons as clang is too old)
> +      $(warning Warning: Disabled BPF skeletons as clang is too old)
>        BUILD_BPF_SKEL := 0
>      endif
>    endif
> @@ -727,7 +727,7 @@ dwarf-post-unwind-text := BUG
>  # setup DWARF post unwinder
>  ifdef NO_LIBUNWIND
>    ifdef NO_LIBDW_DWARF_UNWIND
> -    msg := $(warning Disabling post unwind, no support found.);
> +    $(warning Disabling post unwind, no support found.)
>      dwarf-post-unwind := 0
>    else
>      dwarf-post-unwind-text := libdw
> @@ -753,7 +753,7 @@ ifndef NO_LOCAL_LIBUNWIND
>    ifeq ($(SRCARCH),$(filter $(SRCARCH),arm arm64))
>      $(call feature_check,libunwind-debug-frame)
>      ifneq ($(feature-libunwind-debug-frame), 1)
> -      msg := $(warning No debug_frame support found in libunwind);
> +      $(warning No debug_frame support found in libunwind)
>        CFLAGS += -DNO_LIBUNWIND_DEBUG_FRAME
>      endif
>    else
> @@ -782,7 +782,7 @@ ifneq ($(NO_LIBTRACEEVENT),1)
>      ifndef NO_LIBAUDIT
>        $(call feature_check,libaudit)
>        ifneq ($(feature-libaudit), 1)
> -        msg := $(warning No libaudit.h found, disables 'trace' tool, please install audit-libs-devel or libaudit-dev);
> +        $(warning No libaudit.h found, disables 'trace' tool, please install audit-libs-devel or libaudit-dev)
>          NO_LIBAUDIT := 1
>        else
>          CFLAGS += -DHAVE_LIBAUDIT_SUPPORT
> @@ -795,7 +795,7 @@ endif
>  
>  ifndef NO_LIBCRYPTO
>    ifneq ($(feature-libcrypto), 1)
> -    msg := $(warning No libcrypto.h found, disables jitted code injection, please install openssl-devel or libssl-dev);
> +    $(warning No libcrypto.h found, disables jitted code injection, please install openssl-devel or libssl-dev)
>      NO_LIBCRYPTO := 1
>    else
>      CFLAGS += -DHAVE_LIBCRYPTO_SUPPORT
> @@ -807,7 +807,7 @@ endif
>  ifndef NO_SLANG
>    ifneq ($(feature-libslang), 1)
>      ifneq ($(feature-libslang-include-subdir), 1)
> -      msg := $(warning slang not found, disables TUI support. Please install slang-devel, libslang-dev or libslang2-dev);
> +      $(warning slang not found, disables TUI support. Please install slang-devel, libslang-dev or libslang2-dev)
>        NO_SLANG := 1
>      else
>        CFLAGS += -DHAVE_SLANG_INCLUDE_SUBDIR
> @@ -825,7 +825,7 @@ ifdef GTK2
>    FLAGS_GTK2=$(CFLAGS) $(LDFLAGS) $(EXTLIBS) $(shell $(PKG_CONFIG) --libs --cflags gtk+-2.0 2>/dev/null)
>    $(call feature_check,gtk2)
>    ifneq ($(feature-gtk2), 1)
> -    msg := $(warning GTK2 not found, disables GTK2 support. Please install gtk2-devel or libgtk2.0-dev);
> +    $(warning GTK2 not found, disables GTK2 support. Please install gtk2-devel or libgtk2.0-dev)
>      NO_GTK2 := 1
>    else
>      $(call feature_check,gtk2-infobar)
> @@ -854,7 +854,7 @@ else
>    ifneq ($(feature-libperl), 1)
>      CFLAGS += -DNO_LIBPERL
>      NO_LIBPERL := 1
> -    msg := $(warning Missing perl devel files. Disabling perl scripting support, please install perl-ExtUtils-Embed/libperl-dev);
> +    $(warning Missing perl devel files. Disabling perl scripting support, please install perl-ExtUtils-Embed/libperl-dev)
>    else
>      LDFLAGS += $(PERL_EMBED_LDFLAGS)
>      EXTLIBS += $(PERL_EMBED_LIBADD)
> @@ -869,7 +869,7 @@ endif
>  ifeq ($(feature-timerfd), 1)
>    CFLAGS += -DHAVE_TIMERFD_SUPPORT
>  else
> -  msg := $(warning No timerfd support. Disables 'perf kvm stat live');
> +  $(warning No timerfd support. Disables 'perf kvm stat live')
>  endif
>  
>  disable-python = $(eval $(disable-python_code))
> @@ -903,7 +903,7 @@ else
>             PYTHON_EXTENSION_SUFFIX := $(shell $(PYTHON) -c 'from importlib import machinery; print(machinery.EXTENSION_SUFFIXES[0])')
>             LANG_BINDINGS += $(obj-perf)python/perf$(PYTHON_EXTENSION_SUFFIX)
>  	 else
> -           msg := $(warning Missing python setuptools, the python binding won't be built, please install python3-setuptools or equivalent);
> +           $(warning Missing python setuptools, the python binding won't be built, please install python3-setuptools or equivalent)
>           endif
>           CFLAGS += -DHAVE_LIBPYTHON_SUPPORT
>           $(call detected,CONFIG_LIBPYTHON)
> @@ -962,7 +962,7 @@ ifdef BUILD_NONDISTRO
>    ifeq ($(feature-libbfd-buildid), 1)
>      CFLAGS += -DHAVE_LIBBFD_BUILDID_SUPPORT
>    else
> -    msg := $(warning Old version of libbfd/binutils things like PE executable profiling will not be available);
> +    $(warning Old version of libbfd/binutils things like PE executable profiling will not be available)
>    endif
>  endif
>  
> @@ -994,7 +994,7 @@ ifndef NO_LZMA
>      EXTLIBS += -llzma
>      $(call detected,CONFIG_LZMA)
>    else
> -    msg := $(warning No liblzma found, disables xz kernel module decompression, please install xz-devel/liblzma-dev);
> +    $(warning No liblzma found, disables xz kernel module decompression, please install xz-devel/liblzma-dev)
>      NO_LZMA := 1
>    endif
>  endif
> @@ -1007,7 +1007,7 @@ ifndef NO_LIBZSTD
>      EXTLIBS += -lzstd
>      $(call detected,CONFIG_ZSTD)
>    else
> -    msg := $(warning No libzstd found, disables trace compression, please install libzstd-dev[el] and/or set LIBZSTD_DIR);
> +    $(warning No libzstd found, disables trace compression, please install libzstd-dev[el] and/or set LIBZSTD_DIR)
>      NO_LIBZSTD := 1
>    endif
>  endif
> @@ -1018,7 +1018,7 @@ ifndef NO_LIBCAP
>      EXTLIBS += -lcap
>      $(call detected,CONFIG_LIBCAP)
>    else
> -    msg := $(warning No libcap found, disables capability support, please install libcap-devel/libcap-dev);
> +    $(warning No libcap found, disables capability support, please install libcap-devel/libcap-dev)
>      NO_LIBCAP := 1
>    endif
>  endif
> @@ -1031,11 +1031,11 @@ endif
>  
>  ifndef NO_LIBNUMA
>    ifeq ($(feature-libnuma), 0)
> -    msg := $(warning No numa.h found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev);
> +    $(warning No numa.h found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev)
>      NO_LIBNUMA := 1
>    else
>      ifeq ($(feature-numa_num_possible_cpus), 0)
> -      msg := $(warning Old numa library found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev >= 2.0.8);
> +      $(warning Old numa library found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev >= 2.0.8)
>        NO_LIBNUMA := 1
>      else
>        CFLAGS += -DHAVE_LIBNUMA_SUPPORT
> @@ -1090,14 +1090,14 @@ ifndef NO_LIBBABELTRACE
>      EXTLIBS += -lbabeltrace-ctf
>      $(call detected,CONFIG_LIBBABELTRACE)
>    else
> -    msg := $(warning No libbabeltrace found, disables 'perf data' CTF format support, please install libbabeltrace-dev[el]/libbabeltrace-ctf-dev);
> +    $(warning No libbabeltrace found, disables 'perf data' CTF format support, please install libbabeltrace-dev[el]/libbabeltrace-ctf-dev)
>    endif
>  endif
>  
>  ifndef NO_AUXTRACE
>    ifeq ($(SRCARCH),x86)
>      ifeq ($(feature-get_cpuid), 0)
> -      msg := $(warning Your gcc lacks the __get_cpuid() builtin, disables support for auxtrace/Intel PT, please install a newer gcc);
> +      $(warning Your gcc lacks the __get_cpuid() builtin, disables support for auxtrace/Intel PT, please install a newer gcc)
>        NO_AUXTRACE := 1
>      endif
>    endif
> @@ -1155,7 +1155,7 @@ ifndef NO_LIBPFM4
>      ASCIIDOC_EXTRA = -aHAVE_LIBPFM=1
>      $(call detected,CONFIG_LIBPFM4)
>    else
> -    msg := $(warning libpfm4 not found, disables libpfm4 support. Please install libpfm4-dev);
> +    $(warning libpfm4 not found, disables libpfm4 support. Please install libpfm4-dev)
>    endif
>  endif
>  
> @@ -1173,7 +1173,7 @@ ifneq ($(NO_LIBTRACEEVENT),1)
>      CFLAGS += -DLIBTRACEEVENT_VERSION=$(LIBTRACEEVENT_VERSION_CPP)
>      $(call detected,CONFIG_LIBTRACEEVENT)
>    else
> -    dummy := $(error ERROR: libtraceevent is missing. Please install libtraceevent-dev/libtraceevent-devel or build with NO_LIBTRACEEVENT=1)
> +    $(error ERROR: libtraceevent is missing. Please install libtraceevent-dev/libtraceevent-devel or build with NO_LIBTRACEEVENT=1)
>    endif
>  
>    $(call feature_check,libtracefs)
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index f8774a9b1377..3707fed8dfde 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -482,7 +482,7 @@ drm_hdr_dir := $(srctree)/tools/include/uapi/drm
>  drm_ioctl_tbl := $(srctree)/tools/perf/trace/beauty/drm_ioctl.sh
>  
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(beauty_ioctl_outdir)' ] || mkdir -p '$(beauty_ioctl_outdir)')
> +$(shell [ -d '$(beauty_ioctl_outdir)' ] || mkdir -p '$(beauty_ioctl_outdir)')
>  
>  $(drm_ioctl_array): $(drm_hdr_dir)/drm.h $(drm_hdr_dir)/i915_drm.h $(drm_ioctl_tbl)
>  	$(Q)$(SHELL) '$(drm_ioctl_tbl)' $(drm_hdr_dir) > $@
> @@ -672,7 +672,7 @@ tests-coresight-targets-clean:
>  all: shell_compatibility_test $(ALL_PROGRAMS) $(LANG_BINDINGS) $(OTHER_PROGRAMS) tests-coresight-targets
>  
>  # Create python binding output directory if not already present
> -_dummy := $(shell [ -d '$(OUTPUT)python' ] || mkdir -p '$(OUTPUT)python')
> +$(shell [ -d '$(OUTPUT)python' ] || mkdir -p '$(OUTPUT)python')
>  
>  $(OUTPUT)python/perf$(PYTHON_EXTENSION_SUFFIX): $(PYTHON_EXT_SRCS) $(PYTHON_EXT_DEPS) $(LIBPERF) $(LIBSUBCMD)
>  	$(QUIET_GEN)LDSHARED="$(CC) -pthread -shared" \
> diff --git a/tools/perf/arch/arm64/Makefile b/tools/perf/arch/arm64/Makefile
> index fab3095fb5d0..5735ed4479bb 100644
> --- a/tools/perf/arch/arm64/Makefile
> +++ b/tools/perf/arch/arm64/Makefile
> @@ -18,7 +18,7 @@ sysprf := $(srctree)/tools/perf/arch/arm64/entry/syscalls/
>  systbl := $(sysprf)/mksyscalltbl
>  
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>  
>  $(header): $(sysdef) $(systbl)
>  	$(Q)$(SHELL) '$(systbl)' '$(CC)' '$(HOSTCC)' $(incpath) $(sysdef) > $@
> diff --git a/tools/perf/arch/loongarch/Makefile b/tools/perf/arch/loongarch/Makefile
> index c392e7af4743..3992a67a87d9 100644
> --- a/tools/perf/arch/loongarch/Makefile
> +++ b/tools/perf/arch/loongarch/Makefile
> @@ -17,7 +17,7 @@ sysprf := $(srctree)/tools/perf/arch/loongarch/entry/syscalls/
>  systbl := $(sysprf)/mksyscalltbl
>  
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>  
>  $(header): $(sysdef) $(systbl)
>  	$(Q)$(SHELL) '$(systbl)' '$(CC)' '$(HOSTCC)' $(incpath) $(sysdef) > $@
> diff --git a/tools/perf/arch/mips/Makefile b/tools/perf/arch/mips/Makefile
> index 8bc09072e3d6..cd0b011b3be5 100644
> --- a/tools/perf/arch/mips/Makefile
> +++ b/tools/perf/arch/mips/Makefile
> @@ -11,7 +11,7 @@ sysdef := $(sysprf)/syscall_n64.tbl
>  systbl := $(sysprf)/mksyscalltbl
>  
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>  
>  $(header): $(sysdef) $(systbl)
>  	$(Q)$(SHELL) '$(systbl)' $(sysdef) > $@
> diff --git a/tools/perf/arch/powerpc/Makefile b/tools/perf/arch/powerpc/Makefile
> index 840ea0e59287..bf6d323574f6 100644
> --- a/tools/perf/arch/powerpc/Makefile
> +++ b/tools/perf/arch/powerpc/Makefile
> @@ -19,7 +19,7 @@ sysdef := $(sysprf)/syscall.tbl
>  systbl := $(sysprf)/mksyscalltbl
>  
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>  
>  $(header64): $(sysdef) $(systbl)
>  	$(Q)$(SHELL) '$(systbl)' '64' $(sysdef) > $@
> diff --git a/tools/perf/arch/s390/Makefile b/tools/perf/arch/s390/Makefile
> index 74bffbea03e2..56994e63b43a 100644
> --- a/tools/perf/arch/s390/Makefile
> +++ b/tools/perf/arch/s390/Makefile
> @@ -17,7 +17,7 @@ sysdef := $(sysprf)/syscall.tbl
>  systbl := $(sysprf)/mksyscalltbl
>  
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>  
>  $(header): $(sysdef) $(systbl)
>  	$(Q)$(SHELL) '$(systbl)' $(sysdef) > $@
> diff --git a/tools/perf/arch/x86/Makefile b/tools/perf/arch/x86/Makefile
> index 5a9f9a7bf07d..8952e00f9b60 100644
> --- a/tools/perf/arch/x86/Makefile
> +++ b/tools/perf/arch/x86/Makefile
> @@ -17,7 +17,7 @@ sys       := $(srctree)/tools/perf/arch/x86/entry/syscalls
>  systbl    := $(sys)/syscalltbl.sh
>  
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>  
>  $(header): $(sys)/syscall_64.tbl $(systbl)
>  	$(Q)$(SHELL) '$(systbl)' $(sys)/syscall_64.tbl 'x86_64' > $@
> diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
> index 6fba29f3222d..0aa4005017c7 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
> @@ -1,7 +1,7 @@
>  # SPDX-License-Identifier: GPL-2.0
>  ifneq ($(O),)
>  ifeq ($(origin O), command line)
> -	dummy := $(if $(shell cd $(PWD); test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)
> +        $(if $(shell cd $(PWD); test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)
>  	ABSOLUTE_O := $(shell cd $(PWD); cd $(O) ; pwd)
>  	OUTPUT := $(ABSOLUTE_O)/$(if $(subdir),$(subdir)/)
>  	COMMAND_O := O=$(ABSOLUTE_O)
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 492e937fab00..14684aeb4b55 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -285,7 +285,7 @@ EXTRA_CLEAN += $(GEN_HDRS) \
>  	       $(TEST_GEN_OBJ) \
>  	       cscope.*
>  
> -x := $(shell mkdir -p $(sort $(dir $(LIBKVM_C_OBJ) $(LIBKVM_S_OBJ))))
> +$(shell mkdir -p $(sort $(dir $(LIBKVM_C_OBJ) $(LIBKVM_S_OBJ))))
>  $(LIBKVM_C_OBJ): $(OUTPUT)/%.o: %.c $(GEN_HDRS)
>  	$(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c $< -o $@
>  
> @@ -298,7 +298,7 @@ $(LIBKVM_S_OBJ): $(OUTPUT)/%.o: %.S $(GEN_HDRS)
>  $(LIBKVM_STRING_OBJ): $(OUTPUT)/%.o: %.c
>  	$(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c -ffreestanding $< -o $@
>  
> -x := $(shell mkdir -p $(sort $(dir $(TEST_GEN_PROGS))))
> +$(shell mkdir -p $(sort $(dir $(TEST_GEN_PROGS))))
>  $(SPLIT_TESTS_OBJS): $(GEN_HDRS)
>  $(TEST_GEN_PROGS): $(LIBKVM_OBJS)
>  $(TEST_GEN_PROGS_EXTENDED): $(LIBKVM_OBJS)
> -- 
> 2.40.1

Namhyung Kim Feb. 22, 2024, 5:08 p.m. UTC | #3

Hello,

On Wed, Feb 21, 2024 at 5:42 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> In Makefiles, $(error ), $(warning ), and $(info ) expand to the empty
> string, as explained in the GNU Make manual [1]:
>  "The result of the expansion of this function is the empty string."
>
> Therefore, they are no-op except for logging purposes.
>
> $(shell ...) expands to the output of the command. It expands to the
> empty string when the command does not print anything to stdout.
> Hence, $(shell mkdir ...) is no-op except for creating the directory.
>
> Remove meaningless assignments.
>
> [1]: https://www.gnu.org/software/make/manual/make.html#Make-Control-Functions
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
>
> This is a treewide cleanup, but in practice, this is touching mostly
> perf Makefiles. I am sending this to perf subsystem.

How do you want to route this?  I can take it to perf tree if you're ok.

Thanks,
Namhyung

>
>
>  tools/perf/Makefile.config           | 90 ++++++++++++++--------------
>  tools/perf/Makefile.perf             |  4 +-
>  tools/perf/arch/arm64/Makefile       |  2 +-
>  tools/perf/arch/loongarch/Makefile   |  2 +-
>  tools/perf/arch/mips/Makefile        |  2 +-
>  tools/perf/arch/powerpc/Makefile     |  2 +-
>  tools/perf/arch/s390/Makefile        |  2 +-
>  tools/perf/arch/x86/Makefile         |  2 +-
>  tools/scripts/Makefile.include       |  2 +-
>  tools/testing/selftests/kvm/Makefile |  4 +-
>  10 files changed, 56 insertions(+), 56 deletions(-)
>
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index aa55850fbc21..6edf9916d41c 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -209,11 +209,11 @@ endif
>  include $(srctree)/tools/scripts/utilities.mak
>
>  ifeq ($(call get-executable,$(FLEX)),)
> -  dummy := $(error Error: $(FLEX) is missing on this system, please install it)
> +  $(error Error: $(FLEX) is missing on this system, please install it)
>  endif
>
>  ifeq ($(call get-executable,$(BISON)),)
> -  dummy := $(error Error: $(BISON) is missing on this system, please install it)
> +  $(error Error: $(BISON) is missing on this system, please install it)
>  endif
>
>  ifneq ($(OUTPUT),)
> @@ -438,46 +438,46 @@ else
>        LIBC_SUPPORT := 1
>      endif
>      ifeq ($(LIBC_SUPPORT),1)
> -      msg := $(error ERROR: No libelf found. Disables 'probe' tool, jvmti and BPF support. Please install libelf-dev, libelf-devel, elfutils-libelf-devel or build with NO_LIBELF=1.)
> +      $(error ERROR: No libelf found. Disables 'probe' tool, jvmti and BPF support. Please install libelf-dev, libelf-devel, elfutils-libelf-devel or build with NO_LIBELF=1.)
>      else
>        ifneq ($(filter s% -fsanitize=address%,$(EXTRA_CFLAGS),),)
>          ifneq ($(shell ldconfig -p | grep libasan >/dev/null 2>&1; echo $$?), 0)
> -          msg := $(error No libasan found, please install libasan);
> +          $(error No libasan found, please install libasan)
>          endif
>        endif
>
>        ifneq ($(filter s% -fsanitize=undefined%,$(EXTRA_CFLAGS),),)
>          ifneq ($(shell ldconfig -p | grep libubsan >/dev/null 2>&1; echo $$?), 0)
> -          msg := $(error No libubsan found, please install libubsan);
> +          $(error No libubsan found, please install libubsan)
>          endif
>        endif
>
>        ifneq ($(filter s% -static%,$(LDFLAGS),),)
> -        msg := $(error No static glibc found, please install glibc-static);
> +        $(error No static glibc found, please install glibc-static)
>        else
> -        msg := $(error No gnu/libc-version.h found, please install glibc-dev[el]);
> +        $(error No gnu/libc-version.h found, please install glibc-dev[el])
>        endif
>      endif
>    else
>      ifndef NO_LIBDW_DWARF_UNWIND
>        ifneq ($(feature-libdw-dwarf-unwind),1)
>          NO_LIBDW_DWARF_UNWIND := 1
> -        msg := $(warning No libdw DWARF unwind found, Please install elfutils-devel/libdw-dev >= 0.158 and/or set LIBDW_DIR);
> +        $(warning No libdw DWARF unwind found, Please install elfutils-devel/libdw-dev >= 0.158 and/or set LIBDW_DIR)
>        endif
>      endif
>      ifneq ($(feature-dwarf), 1)
>        ifndef NO_DWARF
> -        msg := $(warning No libdw.h found or old libdw.h found or elfutils is older than 0.138, disables dwarf support. Please install new elfutils-devel/libdw-dev);
> +        $(warning No libdw.h found or old libdw.h found or elfutils is older than 0.138, disables dwarf support. Please install new elfutils-devel/libdw-dev)
>          NO_DWARF := 1
>        endif
>      else
>        ifneq ($(feature-dwarf_getlocations), 1)
> -        msg := $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.157);
> +        $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.157)
>        else
>          CFLAGS += -DHAVE_DWARF_GETLOCATIONS_SUPPORT
>        endif # dwarf_getlocations
>        ifneq ($(feature-dwarf_getcfi), 1)
> -        msg := $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.142);
> +        $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.142)
>        else
>          CFLAGS += -DHAVE_DWARF_CFI_SUPPORT
>        endif # dwarf_getcfi
> @@ -525,7 +525,7 @@ ifdef CORESIGHT
>        endif
>      endif
>    else
> -    dummy := $(error Error: No libopencsd library found or the version is not up-to-date. Please install recent libopencsd to build with CORESIGHT=1)
> +    $(error Error: No libopencsd library found or the version is not up-to-date. Please install recent libopencsd to build with CORESIGHT=1)
>    endif
>  endif
>
> @@ -551,7 +551,7 @@ ifndef NO_LIBELF
>    ifeq ($(feature-libelf-gelf_getnote), 1)
>      CFLAGS += -DHAVE_GELF_GETNOTE_SUPPORT
>    else
> -    msg := $(warning gelf_getnote() not found on libelf, SDT support disabled);
> +    $(warning gelf_getnote() not found on libelf, SDT support disabled)
>    endif
>
>    ifeq ($(feature-libelf-getshdrstrndx), 1)
> @@ -568,7 +568,7 @@ ifndef NO_LIBELF
>
>    ifndef NO_DWARF
>      ifeq ($(origin PERF_HAVE_DWARF_REGS), undefined)
> -      msg := $(warning DWARF register mappings have not been defined for architecture $(SRCARCH), DWARF support disabled);
> +      $(warning DWARF register mappings have not been defined for architecture $(SRCARCH), DWARF support disabled)
>        NO_DWARF := 1
>      else
>        CFLAGS += -DHAVE_DWARF_SUPPORT $(LIBDW_CFLAGS)
> @@ -590,11 +590,11 @@ ifndef NO_LIBELF
>            $(call detected,CONFIG_LIBBPF)
>            $(call detected,CONFIG_LIBBPF_DYNAMIC)
>          else
> -          dummy := $(error Error: No libbpf devel library found or older than v1.0, please install/update libbpf-devel);
> +          $(error Error: No libbpf devel library found or older than v1.0, please install/update libbpf-devel)
>          endif
>        else
>          ifeq ($(NO_ZLIB), 1)
> -          dummy := $(warning Warning: Statically building libbpf not possible as zlib is missing)
> +          $(warning Warning: Statically building libbpf not possible as zlib is missing)
>            NO_LIBBPF := 1
>          else
>            # Libbpf will be built as a static library from tools/lib/bpf.
> @@ -609,7 +609,7 @@ endif # NO_LIBELF
>
>  ifndef NO_SDT
>    ifneq ($(feature-sdt), 1)
> -    msg := $(warning No sys/sdt.h found, no SDT events are defined, please install systemtap-sdt-devel or systemtap-sdt-dev);
> +    $(warning No sys/sdt.h found, no SDT events are defined, please install systemtap-sdt-devel or systemtap-sdt-dev)
>      NO_SDT := 1;
>    else
>      CFLAGS += -DHAVE_SDT_EVENT
> @@ -651,13 +651,13 @@ ifndef NO_LIBUNWIND
>      have_libunwind = 1
>      $(call feature_check,libunwind-debug-frame-aarch64)
>      ifneq ($(feature-libunwind-debug-frame-aarch64), 1)
> -      msg := $(warning No debug_frame support found in libunwind-aarch64);
> +      $(warning No debug_frame support found in libunwind-aarch64)
>        CFLAGS += -DNO_LIBUNWIND_DEBUG_FRAME_AARCH64
>      endif
>    endif
>
>    ifneq ($(feature-libunwind), 1)
> -    msg := $(warning No libunwind found. Please install libunwind-dev[el] >= 1.1 and/or set LIBUNWIND_DIR);
> +    $(warning No libunwind found. Please install libunwind-dev[el] >= 1.1 and/or set LIBUNWIND_DIR)
>      NO_LOCAL_LIBUNWIND := 1
>    else
>      have_libunwind := 1
> @@ -673,7 +673,7 @@ endif
>
>  ifndef NO_LIBBPF
>    ifneq ($(feature-bpf), 1)
> -    msg := $(warning BPF API too old. Please install recent kernel headers. BPF support in 'perf record' is disabled.)
> +    $(warning BPF API too old. Please install recent kernel headers. BPF support in 'perf record' is disabled.)
>      NO_LIBBPF := 1
>    endif
>  endif
> @@ -686,28 +686,28 @@ endif
>
>  ifeq ($(BUILD_BPF_SKEL),1)
>    ifeq ($(filter -DHAVE_LIBELF_SUPPORT, $(CFLAGS)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as libelf is required by bpftool)
> +    $(warning Warning: Disabled BPF skeletons as libelf is required by bpftool)
>      BUILD_BPF_SKEL := 0
>    else ifeq ($(filter -DHAVE_ZLIB_SUPPORT, $(CFLAGS)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as zlib is required by bpftool)
> +    $(warning Warning: Disabled BPF skeletons as zlib is required by bpftool)
>      BUILD_BPF_SKEL := 0
>    else ifeq ($(filter -DHAVE_LIBBPF_SUPPORT, $(CFLAGS)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as libbpf is required)
> +    $(warning Warning: Disabled BPF skeletons as libbpf is required)
>      BUILD_BPF_SKEL := 0
>    else ifeq ($(call get-executable,$(CLANG)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as clang ($(CLANG)) is missing)
> +    $(warning Warning: Disabled BPF skeletons as clang ($(CLANG)) is missing)
>      BUILD_BPF_SKEL := 0
>    else
>      CLANG_VERSION := $(shell $(CLANG) --version | head -1 | sed 's/.*clang version \([[:digit:]]\+.[[:digit:]]\+.[[:digit:]]\+\).*/\1/g')
>      ifeq ($(call version-lt3,$(CLANG_VERSION),12.0.1),1)
> -      dummy := $(warning Warning: Disabled BPF skeletons as reliable BTF generation needs at least $(CLANG) version 12.0.1)
> +      $(warning Warning: Disabled BPF skeletons as reliable BTF generation needs at least $(CLANG) version 12.0.1)
>        BUILD_BPF_SKEL := 0
>      endif
>    endif
>    ifeq ($(BUILD_BPF_SKEL),1)
>      $(call feature_check,clang-bpf-co-re)
>      ifeq ($(feature-clang-bpf-co-re), 0)
> -      dummy := $(warning Warning: Disabled BPF skeletons as clang is too old)
> +      $(warning Warning: Disabled BPF skeletons as clang is too old)
>        BUILD_BPF_SKEL := 0
>      endif
>    endif
> @@ -727,7 +727,7 @@ dwarf-post-unwind-text := BUG
>  # setup DWARF post unwinder
>  ifdef NO_LIBUNWIND
>    ifdef NO_LIBDW_DWARF_UNWIND
> -    msg := $(warning Disabling post unwind, no support found.);
> +    $(warning Disabling post unwind, no support found.)
>      dwarf-post-unwind := 0
>    else
>      dwarf-post-unwind-text := libdw
> @@ -753,7 +753,7 @@ ifndef NO_LOCAL_LIBUNWIND
>    ifeq ($(SRCARCH),$(filter $(SRCARCH),arm arm64))
>      $(call feature_check,libunwind-debug-frame)
>      ifneq ($(feature-libunwind-debug-frame), 1)
> -      msg := $(warning No debug_frame support found in libunwind);
> +      $(warning No debug_frame support found in libunwind)
>        CFLAGS += -DNO_LIBUNWIND_DEBUG_FRAME
>      endif
>    else
> @@ -782,7 +782,7 @@ ifneq ($(NO_LIBTRACEEVENT),1)
>      ifndef NO_LIBAUDIT
>        $(call feature_check,libaudit)
>        ifneq ($(feature-libaudit), 1)
> -        msg := $(warning No libaudit.h found, disables 'trace' tool, please install audit-libs-devel or libaudit-dev);
> +        $(warning No libaudit.h found, disables 'trace' tool, please install audit-libs-devel or libaudit-dev)
>          NO_LIBAUDIT := 1
>        else
>          CFLAGS += -DHAVE_LIBAUDIT_SUPPORT
> @@ -795,7 +795,7 @@ endif
>
>  ifndef NO_LIBCRYPTO
>    ifneq ($(feature-libcrypto), 1)
> -    msg := $(warning No libcrypto.h found, disables jitted code injection, please install openssl-devel or libssl-dev);
> +    $(warning No libcrypto.h found, disables jitted code injection, please install openssl-devel or libssl-dev)
>      NO_LIBCRYPTO := 1
>    else
>      CFLAGS += -DHAVE_LIBCRYPTO_SUPPORT
> @@ -807,7 +807,7 @@ endif
>  ifndef NO_SLANG
>    ifneq ($(feature-libslang), 1)
>      ifneq ($(feature-libslang-include-subdir), 1)
> -      msg := $(warning slang not found, disables TUI support. Please install slang-devel, libslang-dev or libslang2-dev);
> +      $(warning slang not found, disables TUI support. Please install slang-devel, libslang-dev or libslang2-dev)
>        NO_SLANG := 1
>      else
>        CFLAGS += -DHAVE_SLANG_INCLUDE_SUBDIR
> @@ -825,7 +825,7 @@ ifdef GTK2
>    FLAGS_GTK2=$(CFLAGS) $(LDFLAGS) $(EXTLIBS) $(shell $(PKG_CONFIG) --libs --cflags gtk+-2.0 2>/dev/null)
>    $(call feature_check,gtk2)
>    ifneq ($(feature-gtk2), 1)
> -    msg := $(warning GTK2 not found, disables GTK2 support. Please install gtk2-devel or libgtk2.0-dev);
> +    $(warning GTK2 not found, disables GTK2 support. Please install gtk2-devel or libgtk2.0-dev)
>      NO_GTK2 := 1
>    else
>      $(call feature_check,gtk2-infobar)
> @@ -854,7 +854,7 @@ else
>    ifneq ($(feature-libperl), 1)
>      CFLAGS += -DNO_LIBPERL
>      NO_LIBPERL := 1
> -    msg := $(warning Missing perl devel files. Disabling perl scripting support, please install perl-ExtUtils-Embed/libperl-dev);
> +    $(warning Missing perl devel files. Disabling perl scripting support, please install perl-ExtUtils-Embed/libperl-dev)
>    else
>      LDFLAGS += $(PERL_EMBED_LDFLAGS)
>      EXTLIBS += $(PERL_EMBED_LIBADD)
> @@ -869,7 +869,7 @@ endif
>  ifeq ($(feature-timerfd), 1)
>    CFLAGS += -DHAVE_TIMERFD_SUPPORT
>  else
> -  msg := $(warning No timerfd support. Disables 'perf kvm stat live');
> +  $(warning No timerfd support. Disables 'perf kvm stat live')
>  endif
>
>  disable-python = $(eval $(disable-python_code))
> @@ -903,7 +903,7 @@ else
>             PYTHON_EXTENSION_SUFFIX := $(shell $(PYTHON) -c 'from importlib import machinery; print(machinery.EXTENSION_SUFFIXES[0])')
>             LANG_BINDINGS += $(obj-perf)python/perf$(PYTHON_EXTENSION_SUFFIX)
>          else
> -           msg := $(warning Missing python setuptools, the python binding won't be built, please install python3-setuptools or equivalent);
> +           $(warning Missing python setuptools, the python binding won't be built, please install python3-setuptools or equivalent)
>           endif
>           CFLAGS += -DHAVE_LIBPYTHON_SUPPORT
>           $(call detected,CONFIG_LIBPYTHON)
> @@ -962,7 +962,7 @@ ifdef BUILD_NONDISTRO
>    ifeq ($(feature-libbfd-buildid), 1)
>      CFLAGS += -DHAVE_LIBBFD_BUILDID_SUPPORT
>    else
> -    msg := $(warning Old version of libbfd/binutils things like PE executable profiling will not be available);
> +    $(warning Old version of libbfd/binutils things like PE executable profiling will not be available)
>    endif
>  endif
>
> @@ -994,7 +994,7 @@ ifndef NO_LZMA
>      EXTLIBS += -llzma
>      $(call detected,CONFIG_LZMA)
>    else
> -    msg := $(warning No liblzma found, disables xz kernel module decompression, please install xz-devel/liblzma-dev);
> +    $(warning No liblzma found, disables xz kernel module decompression, please install xz-devel/liblzma-dev)
>      NO_LZMA := 1
>    endif
>  endif
> @@ -1007,7 +1007,7 @@ ifndef NO_LIBZSTD
>      EXTLIBS += -lzstd
>      $(call detected,CONFIG_ZSTD)
>    else
> -    msg := $(warning No libzstd found, disables trace compression, please install libzstd-dev[el] and/or set LIBZSTD_DIR);
> +    $(warning No libzstd found, disables trace compression, please install libzstd-dev[el] and/or set LIBZSTD_DIR)
>      NO_LIBZSTD := 1
>    endif
>  endif
> @@ -1018,7 +1018,7 @@ ifndef NO_LIBCAP
>      EXTLIBS += -lcap
>      $(call detected,CONFIG_LIBCAP)
>    else
> -    msg := $(warning No libcap found, disables capability support, please install libcap-devel/libcap-dev);
> +    $(warning No libcap found, disables capability support, please install libcap-devel/libcap-dev)
>      NO_LIBCAP := 1
>    endif
>  endif
> @@ -1031,11 +1031,11 @@ endif
>
>  ifndef NO_LIBNUMA
>    ifeq ($(feature-libnuma), 0)
> -    msg := $(warning No numa.h found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev);
> +    $(warning No numa.h found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev)
>      NO_LIBNUMA := 1
>    else
>      ifeq ($(feature-numa_num_possible_cpus), 0)
> -      msg := $(warning Old numa library found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev >= 2.0.8);
> +      $(warning Old numa library found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev >= 2.0.8)
>        NO_LIBNUMA := 1
>      else
>        CFLAGS += -DHAVE_LIBNUMA_SUPPORT
> @@ -1090,14 +1090,14 @@ ifndef NO_LIBBABELTRACE
>      EXTLIBS += -lbabeltrace-ctf
>      $(call detected,CONFIG_LIBBABELTRACE)
>    else
> -    msg := $(warning No libbabeltrace found, disables 'perf data' CTF format support, please install libbabeltrace-dev[el]/libbabeltrace-ctf-dev);
> +    $(warning No libbabeltrace found, disables 'perf data' CTF format support, please install libbabeltrace-dev[el]/libbabeltrace-ctf-dev)
>    endif
>  endif
>
>  ifndef NO_AUXTRACE
>    ifeq ($(SRCARCH),x86)
>      ifeq ($(feature-get_cpuid), 0)
> -      msg := $(warning Your gcc lacks the __get_cpuid() builtin, disables support for auxtrace/Intel PT, please install a newer gcc);
> +      $(warning Your gcc lacks the __get_cpuid() builtin, disables support for auxtrace/Intel PT, please install a newer gcc)
>        NO_AUXTRACE := 1
>      endif
>    endif
> @@ -1155,7 +1155,7 @@ ifndef NO_LIBPFM4
>      ASCIIDOC_EXTRA = -aHAVE_LIBPFM=1
>      $(call detected,CONFIG_LIBPFM4)
>    else
> -    msg := $(warning libpfm4 not found, disables libpfm4 support. Please install libpfm4-dev);
> +    $(warning libpfm4 not found, disables libpfm4 support. Please install libpfm4-dev)
>    endif
>  endif
>
> @@ -1173,7 +1173,7 @@ ifneq ($(NO_LIBTRACEEVENT),1)
>      CFLAGS += -DLIBTRACEEVENT_VERSION=$(LIBTRACEEVENT_VERSION_CPP)
>      $(call detected,CONFIG_LIBTRACEEVENT)
>    else
> -    dummy := $(error ERROR: libtraceevent is missing. Please install libtraceevent-dev/libtraceevent-devel or build with NO_LIBTRACEEVENT=1)
> +    $(error ERROR: libtraceevent is missing. Please install libtraceevent-dev/libtraceevent-devel or build with NO_LIBTRACEEVENT=1)
>    endif
>
>    $(call feature_check,libtracefs)
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index f8774a9b1377..3707fed8dfde 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -482,7 +482,7 @@ drm_hdr_dir := $(srctree)/tools/include/uapi/drm
>  drm_ioctl_tbl := $(srctree)/tools/perf/trace/beauty/drm_ioctl.sh
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(beauty_ioctl_outdir)' ] || mkdir -p '$(beauty_ioctl_outdir)')
> +$(shell [ -d '$(beauty_ioctl_outdir)' ] || mkdir -p '$(beauty_ioctl_outdir)')
>
>  $(drm_ioctl_array): $(drm_hdr_dir)/drm.h $(drm_hdr_dir)/i915_drm.h $(drm_ioctl_tbl)
>         $(Q)$(SHELL) '$(drm_ioctl_tbl)' $(drm_hdr_dir) > $@
> @@ -672,7 +672,7 @@ tests-coresight-targets-clean:
>  all: shell_compatibility_test $(ALL_PROGRAMS) $(LANG_BINDINGS) $(OTHER_PROGRAMS) tests-coresight-targets
>
>  # Create python binding output directory if not already present
> -_dummy := $(shell [ -d '$(OUTPUT)python' ] || mkdir -p '$(OUTPUT)python')
> +$(shell [ -d '$(OUTPUT)python' ] || mkdir -p '$(OUTPUT)python')
>
>  $(OUTPUT)python/perf$(PYTHON_EXTENSION_SUFFIX): $(PYTHON_EXT_SRCS) $(PYTHON_EXT_DEPS) $(LIBPERF) $(LIBSUBCMD)
>         $(QUIET_GEN)LDSHARED="$(CC) -pthread -shared" \
> diff --git a/tools/perf/arch/arm64/Makefile b/tools/perf/arch/arm64/Makefile
> index fab3095fb5d0..5735ed4479bb 100644
> --- a/tools/perf/arch/arm64/Makefile
> +++ b/tools/perf/arch/arm64/Makefile
> @@ -18,7 +18,7 @@ sysprf := $(srctree)/tools/perf/arch/arm64/entry/syscalls/
>  systbl := $(sysprf)/mksyscalltbl
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>
>  $(header): $(sysdef) $(systbl)
>         $(Q)$(SHELL) '$(systbl)' '$(CC)' '$(HOSTCC)' $(incpath) $(sysdef) > $@
> diff --git a/tools/perf/arch/loongarch/Makefile b/tools/perf/arch/loongarch/Makefile
> index c392e7af4743..3992a67a87d9 100644
> --- a/tools/perf/arch/loongarch/Makefile
> +++ b/tools/perf/arch/loongarch/Makefile
> @@ -17,7 +17,7 @@ sysprf := $(srctree)/tools/perf/arch/loongarch/entry/syscalls/
>  systbl := $(sysprf)/mksyscalltbl
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>
>  $(header): $(sysdef) $(systbl)
>         $(Q)$(SHELL) '$(systbl)' '$(CC)' '$(HOSTCC)' $(incpath) $(sysdef) > $@
> diff --git a/tools/perf/arch/mips/Makefile b/tools/perf/arch/mips/Makefile
> index 8bc09072e3d6..cd0b011b3be5 100644
> --- a/tools/perf/arch/mips/Makefile
> +++ b/tools/perf/arch/mips/Makefile
> @@ -11,7 +11,7 @@ sysdef := $(sysprf)/syscall_n64.tbl
>  systbl := $(sysprf)/mksyscalltbl
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>
>  $(header): $(sysdef) $(systbl)
>         $(Q)$(SHELL) '$(systbl)' $(sysdef) > $@
> diff --git a/tools/perf/arch/powerpc/Makefile b/tools/perf/arch/powerpc/Makefile
> index 840ea0e59287..bf6d323574f6 100644
> --- a/tools/perf/arch/powerpc/Makefile
> +++ b/tools/perf/arch/powerpc/Makefile
> @@ -19,7 +19,7 @@ sysdef := $(sysprf)/syscall.tbl
>  systbl := $(sysprf)/mksyscalltbl
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>
>  $(header64): $(sysdef) $(systbl)
>         $(Q)$(SHELL) '$(systbl)' '64' $(sysdef) > $@
> diff --git a/tools/perf/arch/s390/Makefile b/tools/perf/arch/s390/Makefile
> index 74bffbea03e2..56994e63b43a 100644
> --- a/tools/perf/arch/s390/Makefile
> +++ b/tools/perf/arch/s390/Makefile
> @@ -17,7 +17,7 @@ sysdef := $(sysprf)/syscall.tbl
>  systbl := $(sysprf)/mksyscalltbl
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>
>  $(header): $(sysdef) $(systbl)
>         $(Q)$(SHELL) '$(systbl)' $(sysdef) > $@
> diff --git a/tools/perf/arch/x86/Makefile b/tools/perf/arch/x86/Makefile
> index 5a9f9a7bf07d..8952e00f9b60 100644
> --- a/tools/perf/arch/x86/Makefile
> +++ b/tools/perf/arch/x86/Makefile
> @@ -17,7 +17,7 @@ sys       := $(srctree)/tools/perf/arch/x86/entry/syscalls
>  systbl    := $(sys)/syscalltbl.sh
>
>  # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>
>  $(header): $(sys)/syscall_64.tbl $(systbl)
>         $(Q)$(SHELL) '$(systbl)' $(sys)/syscall_64.tbl 'x86_64' > $@
> diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
> index 6fba29f3222d..0aa4005017c7 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
> @@ -1,7 +1,7 @@
>  # SPDX-License-Identifier: GPL-2.0
>  ifneq ($(O),)
>  ifeq ($(origin O), command line)
> -       dummy := $(if $(shell cd $(PWD); test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)
> +        $(if $(shell cd $(PWD); test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)
>         ABSOLUTE_O := $(shell cd $(PWD); cd $(O) ; pwd)
>         OUTPUT := $(ABSOLUTE_O)/$(if $(subdir),$(subdir)/)
>         COMMAND_O := O=$(ABSOLUTE_O)
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 492e937fab00..14684aeb4b55 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -285,7 +285,7 @@ EXTRA_CLEAN += $(GEN_HDRS) \
>                $(TEST_GEN_OBJ) \
>                cscope.*
>
> -x := $(shell mkdir -p $(sort $(dir $(LIBKVM_C_OBJ) $(LIBKVM_S_OBJ))))
> +$(shell mkdir -p $(sort $(dir $(LIBKVM_C_OBJ) $(LIBKVM_S_OBJ))))
>  $(LIBKVM_C_OBJ): $(OUTPUT)/%.o: %.c $(GEN_HDRS)
>         $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c $< -o $@
>
> @@ -298,7 +298,7 @@ $(LIBKVM_S_OBJ): $(OUTPUT)/%.o: %.S $(GEN_HDRS)
>  $(LIBKVM_STRING_OBJ): $(OUTPUT)/%.o: %.c
>         $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c -ffreestanding $< -o $@
>
> -x := $(shell mkdir -p $(sort $(dir $(TEST_GEN_PROGS))))
> +$(shell mkdir -p $(sort $(dir $(TEST_GEN_PROGS))))
>  $(SPLIT_TESTS_OBJS): $(GEN_HDRS)
>  $(TEST_GEN_PROGS): $(LIBKVM_OBJS)
>  $(TEST_GEN_PROGS_EXTENDED): $(LIBKVM_OBJS)
> --
> 2.40.1
>

Masahiro Yamada Feb. 23, 2024, 2:25 a.m. UTC | #4

On Fri, Feb 23, 2024 at 2:08 AM Namhyung Kim <namhyung@kernel.org> wrote:
>
> Hello,
>
> On Wed, Feb 21, 2024 at 5:42 AM Masahiro Yamada <masahiroy@kernel.org> wrote:
> >
> > In Makefiles, $(error ), $(warning ), and $(info ) expand to the empty
> > string, as explained in the GNU Make manual [1]:
> >  "The result of the expansion of this function is the empty string."
> >
> > Therefore, they are no-op except for logging purposes.
> >
> > $(shell ...) expands to the output of the command. It expands to the
> > empty string when the command does not print anything to stdout.
> > Hence, $(shell mkdir ...) is no-op except for creating the directory.
> >
> > Remove meaningless assignments.
> >
> > [1]: https://www.gnu.org/software/make/manual/make.html#Make-Control-Functions
> >
> > Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> > ---
> >
> > This is a treewide cleanup, but in practice, this is touching mostly
> > perf Makefiles. I am sending this to perf subsystem.
>
> How do you want to route this?  I can take it to perf tree if you're ok.


Yes, that is my expectation because it will reduce the risk
of merge conflicts.

I only included the perf maintainers and ML to To:,
and anything else in CC:

Namhyung Kim Feb. 26, 2024, 4:20 p.m. UTC | #5

On Wed, 21 Feb 2024 22:42:01 +0900, Masahiro Yamada wrote:
> In Makefiles, $(error ), $(warning ), and $(info ) expand to the empty
> string, as explained in the GNU Make manual [1]:
>  "The result of the expansion of this function is the empty string."
> 
> Therefore, they are no-op except for logging purposes.
> 
> $(shell ...) expands to the output of the command. It expands to the
> empty string when the command does not print anything to stdout.
> Hence, $(shell mkdir ...) is no-op except for creating the directory.
> 
> [...]

Applied to perf-tools-next, thanks!

Best regards,

Paolo Bonzini March 15, 2024, 10:49 a.m. UTC | #6

On 2/21/24 14:42, Masahiro Yamada wrote:
> In Makefiles, $(error ), $(warning ), and $(info ) expand to the empty
> string, as explained in the GNU Make manual [1]:
>   "The result of the expansion of this function is the empty string."
> 
> Therefore, they are no-op except for logging purposes.
> 
> $(shell ...) expands to the output of the command. It expands to the
> empty string when the command does not print anything to stdout.
> Hence, $(shell mkdir ...) is no-op except for creating the directory.
> 
> Remove meaningless assignments.
> 
> [1]: https://www.gnu.org/software/make/manual/make.html#Make-Control-Functions
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
> 
> This is a treewide cleanup, but in practice, this is touching mostly
> perf Makefiles. I am sending this to perf subsystem.

"Mostly" is not exclusively, and you did not even bother CCing the KVM 
mailing list.  We would have told you that we have changes in flight for 
6.9, and now there are conflicts in the file that you touched.

Next time please prepare a topic branch, or split the patch.

Paolo

> 
>   tools/perf/Makefile.config           | 90 ++++++++++++++--------------
>   tools/perf/Makefile.perf             |  4 +-
>   tools/perf/arch/arm64/Makefile       |  2 +-
>   tools/perf/arch/loongarch/Makefile   |  2 +-
>   tools/perf/arch/mips/Makefile        |  2 +-
>   tools/perf/arch/powerpc/Makefile     |  2 +-
>   tools/perf/arch/s390/Makefile        |  2 +-
>   tools/perf/arch/x86/Makefile         |  2 +-
>   tools/scripts/Makefile.include       |  2 +-
>   tools/testing/selftests/kvm/Makefile |  4 +-
>   10 files changed, 56 insertions(+), 56 deletions(-)
> 
> diff --git a/tools/perf/Makefile.config b/tools/perf/Makefile.config
> index aa55850fbc21..6edf9916d41c 100644
> --- a/tools/perf/Makefile.config
> +++ b/tools/perf/Makefile.config
> @@ -209,11 +209,11 @@ endif
>   include $(srctree)/tools/scripts/utilities.mak
>   
>   ifeq ($(call get-executable,$(FLEX)),)
> -  dummy := $(error Error: $(FLEX) is missing on this system, please install it)
> +  $(error Error: $(FLEX) is missing on this system, please install it)
>   endif
>   
>   ifeq ($(call get-executable,$(BISON)),)
> -  dummy := $(error Error: $(BISON) is missing on this system, please install it)
> +  $(error Error: $(BISON) is missing on this system, please install it)
>   endif
>   
>   ifneq ($(OUTPUT),)
> @@ -438,46 +438,46 @@ else
>         LIBC_SUPPORT := 1
>       endif
>       ifeq ($(LIBC_SUPPORT),1)
> -      msg := $(error ERROR: No libelf found. Disables 'probe' tool, jvmti and BPF support. Please install libelf-dev, libelf-devel, elfutils-libelf-devel or build with NO_LIBELF=1.)
> +      $(error ERROR: No libelf found. Disables 'probe' tool, jvmti and BPF support. Please install libelf-dev, libelf-devel, elfutils-libelf-devel or build with NO_LIBELF=1.)
>       else
>         ifneq ($(filter s% -fsanitize=address%,$(EXTRA_CFLAGS),),)
>           ifneq ($(shell ldconfig -p | grep libasan >/dev/null 2>&1; echo $$?), 0)
> -          msg := $(error No libasan found, please install libasan);
> +          $(error No libasan found, please install libasan)
>           endif
>         endif
>   
>         ifneq ($(filter s% -fsanitize=undefined%,$(EXTRA_CFLAGS),),)
>           ifneq ($(shell ldconfig -p | grep libubsan >/dev/null 2>&1; echo $$?), 0)
> -          msg := $(error No libubsan found, please install libubsan);
> +          $(error No libubsan found, please install libubsan)
>           endif
>         endif
>   
>         ifneq ($(filter s% -static%,$(LDFLAGS),),)
> -        msg := $(error No static glibc found, please install glibc-static);
> +        $(error No static glibc found, please install glibc-static)
>         else
> -        msg := $(error No gnu/libc-version.h found, please install glibc-dev[el]);
> +        $(error No gnu/libc-version.h found, please install glibc-dev[el])
>         endif
>       endif
>     else
>       ifndef NO_LIBDW_DWARF_UNWIND
>         ifneq ($(feature-libdw-dwarf-unwind),1)
>           NO_LIBDW_DWARF_UNWIND := 1
> -        msg := $(warning No libdw DWARF unwind found, Please install elfutils-devel/libdw-dev >= 0.158 and/or set LIBDW_DIR);
> +        $(warning No libdw DWARF unwind found, Please install elfutils-devel/libdw-dev >= 0.158 and/or set LIBDW_DIR)
>         endif
>       endif
>       ifneq ($(feature-dwarf), 1)
>         ifndef NO_DWARF
> -        msg := $(warning No libdw.h found or old libdw.h found or elfutils is older than 0.138, disables dwarf support. Please install new elfutils-devel/libdw-dev);
> +        $(warning No libdw.h found or old libdw.h found or elfutils is older than 0.138, disables dwarf support. Please install new elfutils-devel/libdw-dev)
>           NO_DWARF := 1
>         endif
>       else
>         ifneq ($(feature-dwarf_getlocations), 1)
> -        msg := $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.157);
> +        $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.157)
>         else
>           CFLAGS += -DHAVE_DWARF_GETLOCATIONS_SUPPORT
>         endif # dwarf_getlocations
>         ifneq ($(feature-dwarf_getcfi), 1)
> -        msg := $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.142);
> +        $(warning Old libdw.h, finding variables at given 'perf probe' point will not work, install elfutils-devel/libdw-dev >= 0.142)
>         else
>           CFLAGS += -DHAVE_DWARF_CFI_SUPPORT
>         endif # dwarf_getcfi
> @@ -525,7 +525,7 @@ ifdef CORESIGHT
>         endif
>       endif
>     else
> -    dummy := $(error Error: No libopencsd library found or the version is not up-to-date. Please install recent libopencsd to build with CORESIGHT=1)
> +    $(error Error: No libopencsd library found or the version is not up-to-date. Please install recent libopencsd to build with CORESIGHT=1)
>     endif
>   endif
>   
> @@ -551,7 +551,7 @@ ifndef NO_LIBELF
>     ifeq ($(feature-libelf-gelf_getnote), 1)
>       CFLAGS += -DHAVE_GELF_GETNOTE_SUPPORT
>     else
> -    msg := $(warning gelf_getnote() not found on libelf, SDT support disabled);
> +    $(warning gelf_getnote() not found on libelf, SDT support disabled)
>     endif
>   
>     ifeq ($(feature-libelf-getshdrstrndx), 1)
> @@ -568,7 +568,7 @@ ifndef NO_LIBELF
>   
>     ifndef NO_DWARF
>       ifeq ($(origin PERF_HAVE_DWARF_REGS), undefined)
> -      msg := $(warning DWARF register mappings have not been defined for architecture $(SRCARCH), DWARF support disabled);
> +      $(warning DWARF register mappings have not been defined for architecture $(SRCARCH), DWARF support disabled)
>         NO_DWARF := 1
>       else
>         CFLAGS += -DHAVE_DWARF_SUPPORT $(LIBDW_CFLAGS)
> @@ -590,11 +590,11 @@ ifndef NO_LIBELF
>             $(call detected,CONFIG_LIBBPF)
>             $(call detected,CONFIG_LIBBPF_DYNAMIC)
>           else
> -          dummy := $(error Error: No libbpf devel library found or older than v1.0, please install/update libbpf-devel);
> +          $(error Error: No libbpf devel library found or older than v1.0, please install/update libbpf-devel)
>           endif
>         else
>           ifeq ($(NO_ZLIB), 1)
> -          dummy := $(warning Warning: Statically building libbpf not possible as zlib is missing)
> +          $(warning Warning: Statically building libbpf not possible as zlib is missing)
>             NO_LIBBPF := 1
>           else
>             # Libbpf will be built as a static library from tools/lib/bpf.
> @@ -609,7 +609,7 @@ endif # NO_LIBELF
>   
>   ifndef NO_SDT
>     ifneq ($(feature-sdt), 1)
> -    msg := $(warning No sys/sdt.h found, no SDT events are defined, please install systemtap-sdt-devel or systemtap-sdt-dev);
> +    $(warning No sys/sdt.h found, no SDT events are defined, please install systemtap-sdt-devel or systemtap-sdt-dev)
>       NO_SDT := 1;
>     else
>       CFLAGS += -DHAVE_SDT_EVENT
> @@ -651,13 +651,13 @@ ifndef NO_LIBUNWIND
>       have_libunwind = 1
>       $(call feature_check,libunwind-debug-frame-aarch64)
>       ifneq ($(feature-libunwind-debug-frame-aarch64), 1)
> -      msg := $(warning No debug_frame support found in libunwind-aarch64);
> +      $(warning No debug_frame support found in libunwind-aarch64)
>         CFLAGS += -DNO_LIBUNWIND_DEBUG_FRAME_AARCH64
>       endif
>     endif
>   
>     ifneq ($(feature-libunwind), 1)
> -    msg := $(warning No libunwind found. Please install libunwind-dev[el] >= 1.1 and/or set LIBUNWIND_DIR);
> +    $(warning No libunwind found. Please install libunwind-dev[el] >= 1.1 and/or set LIBUNWIND_DIR)
>       NO_LOCAL_LIBUNWIND := 1
>     else
>       have_libunwind := 1
> @@ -673,7 +673,7 @@ endif
>   
>   ifndef NO_LIBBPF
>     ifneq ($(feature-bpf), 1)
> -    msg := $(warning BPF API too old. Please install recent kernel headers. BPF support in 'perf record' is disabled.)
> +    $(warning BPF API too old. Please install recent kernel headers. BPF support in 'perf record' is disabled.)
>       NO_LIBBPF := 1
>     endif
>   endif
> @@ -686,28 +686,28 @@ endif
>   
>   ifeq ($(BUILD_BPF_SKEL),1)
>     ifeq ($(filter -DHAVE_LIBELF_SUPPORT, $(CFLAGS)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as libelf is required by bpftool)
> +    $(warning Warning: Disabled BPF skeletons as libelf is required by bpftool)
>       BUILD_BPF_SKEL := 0
>     else ifeq ($(filter -DHAVE_ZLIB_SUPPORT, $(CFLAGS)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as zlib is required by bpftool)
> +    $(warning Warning: Disabled BPF skeletons as zlib is required by bpftool)
>       BUILD_BPF_SKEL := 0
>     else ifeq ($(filter -DHAVE_LIBBPF_SUPPORT, $(CFLAGS)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as libbpf is required)
> +    $(warning Warning: Disabled BPF skeletons as libbpf is required)
>       BUILD_BPF_SKEL := 0
>     else ifeq ($(call get-executable,$(CLANG)),)
> -    dummy := $(warning Warning: Disabled BPF skeletons as clang ($(CLANG)) is missing)
> +    $(warning Warning: Disabled BPF skeletons as clang ($(CLANG)) is missing)
>       BUILD_BPF_SKEL := 0
>     else
>       CLANG_VERSION := $(shell $(CLANG) --version | head -1 | sed 's/.*clang version \([[:digit:]]\+.[[:digit:]]\+.[[:digit:]]\+\).*/\1/g')
>       ifeq ($(call version-lt3,$(CLANG_VERSION),12.0.1),1)
> -      dummy := $(warning Warning: Disabled BPF skeletons as reliable BTF generation needs at least $(CLANG) version 12.0.1)
> +      $(warning Warning: Disabled BPF skeletons as reliable BTF generation needs at least $(CLANG) version 12.0.1)
>         BUILD_BPF_SKEL := 0
>       endif
>     endif
>     ifeq ($(BUILD_BPF_SKEL),1)
>       $(call feature_check,clang-bpf-co-re)
>       ifeq ($(feature-clang-bpf-co-re), 0)
> -      dummy := $(warning Warning: Disabled BPF skeletons as clang is too old)
> +      $(warning Warning: Disabled BPF skeletons as clang is too old)
>         BUILD_BPF_SKEL := 0
>       endif
>     endif
> @@ -727,7 +727,7 @@ dwarf-post-unwind-text := BUG
>   # setup DWARF post unwinder
>   ifdef NO_LIBUNWIND
>     ifdef NO_LIBDW_DWARF_UNWIND
> -    msg := $(warning Disabling post unwind, no support found.);
> +    $(warning Disabling post unwind, no support found.)
>       dwarf-post-unwind := 0
>     else
>       dwarf-post-unwind-text := libdw
> @@ -753,7 +753,7 @@ ifndef NO_LOCAL_LIBUNWIND
>     ifeq ($(SRCARCH),$(filter $(SRCARCH),arm arm64))
>       $(call feature_check,libunwind-debug-frame)
>       ifneq ($(feature-libunwind-debug-frame), 1)
> -      msg := $(warning No debug_frame support found in libunwind);
> +      $(warning No debug_frame support found in libunwind)
>         CFLAGS += -DNO_LIBUNWIND_DEBUG_FRAME
>       endif
>     else
> @@ -782,7 +782,7 @@ ifneq ($(NO_LIBTRACEEVENT),1)
>       ifndef NO_LIBAUDIT
>         $(call feature_check,libaudit)
>         ifneq ($(feature-libaudit), 1)
> -        msg := $(warning No libaudit.h found, disables 'trace' tool, please install audit-libs-devel or libaudit-dev);
> +        $(warning No libaudit.h found, disables 'trace' tool, please install audit-libs-devel or libaudit-dev)
>           NO_LIBAUDIT := 1
>         else
>           CFLAGS += -DHAVE_LIBAUDIT_SUPPORT
> @@ -795,7 +795,7 @@ endif
>   
>   ifndef NO_LIBCRYPTO
>     ifneq ($(feature-libcrypto), 1)
> -    msg := $(warning No libcrypto.h found, disables jitted code injection, please install openssl-devel or libssl-dev);
> +    $(warning No libcrypto.h found, disables jitted code injection, please install openssl-devel or libssl-dev)
>       NO_LIBCRYPTO := 1
>     else
>       CFLAGS += -DHAVE_LIBCRYPTO_SUPPORT
> @@ -807,7 +807,7 @@ endif
>   ifndef NO_SLANG
>     ifneq ($(feature-libslang), 1)
>       ifneq ($(feature-libslang-include-subdir), 1)
> -      msg := $(warning slang not found, disables TUI support. Please install slang-devel, libslang-dev or libslang2-dev);
> +      $(warning slang not found, disables TUI support. Please install slang-devel, libslang-dev or libslang2-dev)
>         NO_SLANG := 1
>       else
>         CFLAGS += -DHAVE_SLANG_INCLUDE_SUBDIR
> @@ -825,7 +825,7 @@ ifdef GTK2
>     FLAGS_GTK2=$(CFLAGS) $(LDFLAGS) $(EXTLIBS) $(shell $(PKG_CONFIG) --libs --cflags gtk+-2.0 2>/dev/null)
>     $(call feature_check,gtk2)
>     ifneq ($(feature-gtk2), 1)
> -    msg := $(warning GTK2 not found, disables GTK2 support. Please install gtk2-devel or libgtk2.0-dev);
> +    $(warning GTK2 not found, disables GTK2 support. Please install gtk2-devel or libgtk2.0-dev)
>       NO_GTK2 := 1
>     else
>       $(call feature_check,gtk2-infobar)
> @@ -854,7 +854,7 @@ else
>     ifneq ($(feature-libperl), 1)
>       CFLAGS += -DNO_LIBPERL
>       NO_LIBPERL := 1
> -    msg := $(warning Missing perl devel files. Disabling perl scripting support, please install perl-ExtUtils-Embed/libperl-dev);
> +    $(warning Missing perl devel files. Disabling perl scripting support, please install perl-ExtUtils-Embed/libperl-dev)
>     else
>       LDFLAGS += $(PERL_EMBED_LDFLAGS)
>       EXTLIBS += $(PERL_EMBED_LIBADD)
> @@ -869,7 +869,7 @@ endif
>   ifeq ($(feature-timerfd), 1)
>     CFLAGS += -DHAVE_TIMERFD_SUPPORT
>   else
> -  msg := $(warning No timerfd support. Disables 'perf kvm stat live');
> +  $(warning No timerfd support. Disables 'perf kvm stat live')
>   endif
>   
>   disable-python = $(eval $(disable-python_code))
> @@ -903,7 +903,7 @@ else
>              PYTHON_EXTENSION_SUFFIX := $(shell $(PYTHON) -c 'from importlib import machinery; print(machinery.EXTENSION_SUFFIXES[0])')
>              LANG_BINDINGS += $(obj-perf)python/perf$(PYTHON_EXTENSION_SUFFIX)
>   	 else
> -           msg := $(warning Missing python setuptools, the python binding won't be built, please install python3-setuptools or equivalent);
> +           $(warning Missing python setuptools, the python binding won't be built, please install python3-setuptools or equivalent)
>            endif
>            CFLAGS += -DHAVE_LIBPYTHON_SUPPORT
>            $(call detected,CONFIG_LIBPYTHON)
> @@ -962,7 +962,7 @@ ifdef BUILD_NONDISTRO
>     ifeq ($(feature-libbfd-buildid), 1)
>       CFLAGS += -DHAVE_LIBBFD_BUILDID_SUPPORT
>     else
> -    msg := $(warning Old version of libbfd/binutils things like PE executable profiling will not be available);
> +    $(warning Old version of libbfd/binutils things like PE executable profiling will not be available)
>     endif
>   endif
>   
> @@ -994,7 +994,7 @@ ifndef NO_LZMA
>       EXTLIBS += -llzma
>       $(call detected,CONFIG_LZMA)
>     else
> -    msg := $(warning No liblzma found, disables xz kernel module decompression, please install xz-devel/liblzma-dev);
> +    $(warning No liblzma found, disables xz kernel module decompression, please install xz-devel/liblzma-dev)
>       NO_LZMA := 1
>     endif
>   endif
> @@ -1007,7 +1007,7 @@ ifndef NO_LIBZSTD
>       EXTLIBS += -lzstd
>       $(call detected,CONFIG_ZSTD)
>     else
> -    msg := $(warning No libzstd found, disables trace compression, please install libzstd-dev[el] and/or set LIBZSTD_DIR);
> +    $(warning No libzstd found, disables trace compression, please install libzstd-dev[el] and/or set LIBZSTD_DIR)
>       NO_LIBZSTD := 1
>     endif
>   endif
> @@ -1018,7 +1018,7 @@ ifndef NO_LIBCAP
>       EXTLIBS += -lcap
>       $(call detected,CONFIG_LIBCAP)
>     else
> -    msg := $(warning No libcap found, disables capability support, please install libcap-devel/libcap-dev);
> +    $(warning No libcap found, disables capability support, please install libcap-devel/libcap-dev)
>       NO_LIBCAP := 1
>     endif
>   endif
> @@ -1031,11 +1031,11 @@ endif
>   
>   ifndef NO_LIBNUMA
>     ifeq ($(feature-libnuma), 0)
> -    msg := $(warning No numa.h found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev);
> +    $(warning No numa.h found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev)
>       NO_LIBNUMA := 1
>     else
>       ifeq ($(feature-numa_num_possible_cpus), 0)
> -      msg := $(warning Old numa library found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev >= 2.0.8);
> +      $(warning Old numa library found, disables 'perf bench numa mem' benchmark, please install numactl-devel/libnuma-devel/libnuma-dev >= 2.0.8)
>         NO_LIBNUMA := 1
>       else
>         CFLAGS += -DHAVE_LIBNUMA_SUPPORT
> @@ -1090,14 +1090,14 @@ ifndef NO_LIBBABELTRACE
>       EXTLIBS += -lbabeltrace-ctf
>       $(call detected,CONFIG_LIBBABELTRACE)
>     else
> -    msg := $(warning No libbabeltrace found, disables 'perf data' CTF format support, please install libbabeltrace-dev[el]/libbabeltrace-ctf-dev);
> +    $(warning No libbabeltrace found, disables 'perf data' CTF format support, please install libbabeltrace-dev[el]/libbabeltrace-ctf-dev)
>     endif
>   endif
>   
>   ifndef NO_AUXTRACE
>     ifeq ($(SRCARCH),x86)
>       ifeq ($(feature-get_cpuid), 0)
> -      msg := $(warning Your gcc lacks the __get_cpuid() builtin, disables support for auxtrace/Intel PT, please install a newer gcc);
> +      $(warning Your gcc lacks the __get_cpuid() builtin, disables support for auxtrace/Intel PT, please install a newer gcc)
>         NO_AUXTRACE := 1
>       endif
>     endif
> @@ -1155,7 +1155,7 @@ ifndef NO_LIBPFM4
>       ASCIIDOC_EXTRA = -aHAVE_LIBPFM=1
>       $(call detected,CONFIG_LIBPFM4)
>     else
> -    msg := $(warning libpfm4 not found, disables libpfm4 support. Please install libpfm4-dev);
> +    $(warning libpfm4 not found, disables libpfm4 support. Please install libpfm4-dev)
>     endif
>   endif
>   
> @@ -1173,7 +1173,7 @@ ifneq ($(NO_LIBTRACEEVENT),1)
>       CFLAGS += -DLIBTRACEEVENT_VERSION=$(LIBTRACEEVENT_VERSION_CPP)
>       $(call detected,CONFIG_LIBTRACEEVENT)
>     else
> -    dummy := $(error ERROR: libtraceevent is missing. Please install libtraceevent-dev/libtraceevent-devel or build with NO_LIBTRACEEVENT=1)
> +    $(error ERROR: libtraceevent is missing. Please install libtraceevent-dev/libtraceevent-devel or build with NO_LIBTRACEEVENT=1)
>     endif
>   
>     $(call feature_check,libtracefs)
> diff --git a/tools/perf/Makefile.perf b/tools/perf/Makefile.perf
> index f8774a9b1377..3707fed8dfde 100644
> --- a/tools/perf/Makefile.perf
> +++ b/tools/perf/Makefile.perf
> @@ -482,7 +482,7 @@ drm_hdr_dir := $(srctree)/tools/include/uapi/drm
>   drm_ioctl_tbl := $(srctree)/tools/perf/trace/beauty/drm_ioctl.sh
>   
>   # Create output directory if not already present
> -_dummy := $(shell [ -d '$(beauty_ioctl_outdir)' ] || mkdir -p '$(beauty_ioctl_outdir)')
> +$(shell [ -d '$(beauty_ioctl_outdir)' ] || mkdir -p '$(beauty_ioctl_outdir)')
>   
>   $(drm_ioctl_array): $(drm_hdr_dir)/drm.h $(drm_hdr_dir)/i915_drm.h $(drm_ioctl_tbl)
>   	$(Q)$(SHELL) '$(drm_ioctl_tbl)' $(drm_hdr_dir) > $@
> @@ -672,7 +672,7 @@ tests-coresight-targets-clean:
>   all: shell_compatibility_test $(ALL_PROGRAMS) $(LANG_BINDINGS) $(OTHER_PROGRAMS) tests-coresight-targets
>   
>   # Create python binding output directory if not already present
> -_dummy := $(shell [ -d '$(OUTPUT)python' ] || mkdir -p '$(OUTPUT)python')
> +$(shell [ -d '$(OUTPUT)python' ] || mkdir -p '$(OUTPUT)python')
>   
>   $(OUTPUT)python/perf$(PYTHON_EXTENSION_SUFFIX): $(PYTHON_EXT_SRCS) $(PYTHON_EXT_DEPS) $(LIBPERF) $(LIBSUBCMD)
>   	$(QUIET_GEN)LDSHARED="$(CC) -pthread -shared" \
> diff --git a/tools/perf/arch/arm64/Makefile b/tools/perf/arch/arm64/Makefile
> index fab3095fb5d0..5735ed4479bb 100644
> --- a/tools/perf/arch/arm64/Makefile
> +++ b/tools/perf/arch/arm64/Makefile
> @@ -18,7 +18,7 @@ sysprf := $(srctree)/tools/perf/arch/arm64/entry/syscalls/
>   systbl := $(sysprf)/mksyscalltbl
>   
>   # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>   
>   $(header): $(sysdef) $(systbl)
>   	$(Q)$(SHELL) '$(systbl)' '$(CC)' '$(HOSTCC)' $(incpath) $(sysdef) > $@
> diff --git a/tools/perf/arch/loongarch/Makefile b/tools/perf/arch/loongarch/Makefile
> index c392e7af4743..3992a67a87d9 100644
> --- a/tools/perf/arch/loongarch/Makefile
> +++ b/tools/perf/arch/loongarch/Makefile
> @@ -17,7 +17,7 @@ sysprf := $(srctree)/tools/perf/arch/loongarch/entry/syscalls/
>   systbl := $(sysprf)/mksyscalltbl
>   
>   # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>   
>   $(header): $(sysdef) $(systbl)
>   	$(Q)$(SHELL) '$(systbl)' '$(CC)' '$(HOSTCC)' $(incpath) $(sysdef) > $@
> diff --git a/tools/perf/arch/mips/Makefile b/tools/perf/arch/mips/Makefile
> index 8bc09072e3d6..cd0b011b3be5 100644
> --- a/tools/perf/arch/mips/Makefile
> +++ b/tools/perf/arch/mips/Makefile
> @@ -11,7 +11,7 @@ sysdef := $(sysprf)/syscall_n64.tbl
>   systbl := $(sysprf)/mksyscalltbl
>   
>   # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>   
>   $(header): $(sysdef) $(systbl)
>   	$(Q)$(SHELL) '$(systbl)' $(sysdef) > $@
> diff --git a/tools/perf/arch/powerpc/Makefile b/tools/perf/arch/powerpc/Makefile
> index 840ea0e59287..bf6d323574f6 100644
> --- a/tools/perf/arch/powerpc/Makefile
> +++ b/tools/perf/arch/powerpc/Makefile
> @@ -19,7 +19,7 @@ sysdef := $(sysprf)/syscall.tbl
>   systbl := $(sysprf)/mksyscalltbl
>   
>   # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>   
>   $(header64): $(sysdef) $(systbl)
>   	$(Q)$(SHELL) '$(systbl)' '64' $(sysdef) > $@
> diff --git a/tools/perf/arch/s390/Makefile b/tools/perf/arch/s390/Makefile
> index 74bffbea03e2..56994e63b43a 100644
> --- a/tools/perf/arch/s390/Makefile
> +++ b/tools/perf/arch/s390/Makefile
> @@ -17,7 +17,7 @@ sysdef := $(sysprf)/syscall.tbl
>   systbl := $(sysprf)/mksyscalltbl
>   
>   # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>   
>   $(header): $(sysdef) $(systbl)
>   	$(Q)$(SHELL) '$(systbl)' $(sysdef) > $@
> diff --git a/tools/perf/arch/x86/Makefile b/tools/perf/arch/x86/Makefile
> index 5a9f9a7bf07d..8952e00f9b60 100644
> --- a/tools/perf/arch/x86/Makefile
> +++ b/tools/perf/arch/x86/Makefile
> @@ -17,7 +17,7 @@ sys       := $(srctree)/tools/perf/arch/x86/entry/syscalls
>   systbl    := $(sys)/syscalltbl.sh
>   
>   # Create output directory if not already present
> -_dummy := $(shell [ -d '$(out)' ] || mkdir -p '$(out)')
> +$(shell [ -d '$(out)' ] || mkdir -p '$(out)')
>   
>   $(header): $(sys)/syscall_64.tbl $(systbl)
>   	$(Q)$(SHELL) '$(systbl)' $(sys)/syscall_64.tbl 'x86_64' > $@
> diff --git a/tools/scripts/Makefile.include b/tools/scripts/Makefile.include
> index 6fba29f3222d..0aa4005017c7 100644
> --- a/tools/scripts/Makefile.include
> +++ b/tools/scripts/Makefile.include
> @@ -1,7 +1,7 @@
>   # SPDX-License-Identifier: GPL-2.0
>   ifneq ($(O),)
>   ifeq ($(origin O), command line)
> -	dummy := $(if $(shell cd $(PWD); test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)
> +        $(if $(shell cd $(PWD); test -d $(O) || echo $(O)),$(error O=$(O) does not exist),)
>   	ABSOLUTE_O := $(shell cd $(PWD); cd $(O) ; pwd)
>   	OUTPUT := $(ABSOLUTE_O)/$(if $(subdir),$(subdir)/)
>   	COMMAND_O := O=$(ABSOLUTE_O)
> diff --git a/tools/testing/selftests/kvm/Makefile b/tools/testing/selftests/kvm/Makefile
> index 492e937fab00..14684aeb4b55 100644
> --- a/tools/testing/selftests/kvm/Makefile
> +++ b/tools/testing/selftests/kvm/Makefile
> @@ -285,7 +285,7 @@ EXTRA_CLEAN += $(GEN_HDRS) \
>   	       $(TEST_GEN_OBJ) \
>   	       cscope.*
>   
> -x := $(shell mkdir -p $(sort $(dir $(LIBKVM_C_OBJ) $(LIBKVM_S_OBJ))))
> +$(shell mkdir -p $(sort $(dir $(LIBKVM_C_OBJ) $(LIBKVM_S_OBJ))))
>   $(LIBKVM_C_OBJ): $(OUTPUT)/%.o: %.c $(GEN_HDRS)
>   	$(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c $< -o $@
>   
> @@ -298,7 +298,7 @@ $(LIBKVM_S_OBJ): $(OUTPUT)/%.o: %.S $(GEN_HDRS)
>   $(LIBKVM_STRING_OBJ): $(OUTPUT)/%.o: %.c
>   	$(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c -ffreestanding $< -o $@
>   
> -x := $(shell mkdir -p $(sort $(dir $(TEST_GEN_PROGS))))
> +$(shell mkdir -p $(sort $(dir $(TEST_GEN_PROGS))))
>   $(SPLIT_TESTS_OBJS): $(GEN_HDRS)
>   $(TEST_GEN_PROGS): $(LIBKVM_OBJS)
>   $(TEST_GEN_PROGS_EXTENDED): $(LIBKVM_OBJS)

treewide: remove meaningless assignments in Makefiles

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