diff mbox series

[v2,bpf-next] compiler-gcc: Suppress -Wmissing-prototypes warning for all supported GCC

Message ID 20231106031802.4188-1-laoar.shao@gmail.com (mailing list archive)
State Accepted
Commit 689b097a06bafb461ec162fc3b3ecc9765cea67b
Delegated to: BPF
Headers show
Series [v2,bpf-next] compiler-gcc: Suppress -Wmissing-prototypes warning for all supported GCC | expand

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Context Check Description
netdev/series_format success Single patches do not need cover letters
netdev/tree_selection success Clearly marked for bpf-next
netdev/fixes_present success Fixes tag not required for -next series
netdev/header_inline success No static functions without inline keyword in header files
netdev/build_32bit success Errors and warnings before: 16002 this patch: 16002
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netdev/checkpatch success total: 0 errors, 0 warnings, 0 checks, 8 lines checked
netdev/build_clang_rust success No Rust files in patch. Skipping build
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Commit Message

Yafang Shao Nov. 6, 2023, 3:18 a.m. UTC 
The kernel supports a minimum GCC version of 5.1.0 for building. However,
the "__diag_ignore_all" directive only suppresses the
"-Wmissing-prototypes" warning for GCC versions >= 8.0.0. As a result, when
building the kernel with older GCC versions, warnings may be triggered. The
example below illustrates the warnings reported by the kernel test robot
using GCC 7.5.0:

  compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
  All warnings (new ones prefixed by >>):

   kernel/bpf/helpers.c:1893:19: warning: no previous prototype for 'bpf_obj_new_impl' [-Wmissing-prototypes]
    __bpf_kfunc void *bpf_obj_new_impl(u64 local_type_id__k, void *meta__ign)
                      ^~~~~~~~~~~~~~~~
   kernel/bpf/helpers.c:1907:19: warning: no previous prototype for 'bpf_percpu_obj_new_impl' [-Wmissing-prototypes]
    __bpf_kfunc void *bpf_percpu_obj_new_impl(u64 local_type_id__k, void *meta__ign)
   [...]

To address this, we should also suppress the "-Wmissing-prototypes" warning
for older GCC versions. "#pragma GCC diagnostic push" is supported as
of GCC 4.6, and both "-Wmissing-prototypes" and "-Wmissing-declarations"
are supported for all the GCC versions that we currently support.
Therefore, it is reasonable to suppress these warnings for all supported
GCC versions.

With this adjustment, it's important to note that after implementing
"__diag_ignore_all", it will effectively suppress warnings for all the
supported GCC versions.

In the future, if you wish to suppress warnings that are only supported on
higher GCC versions, it is advisable to explicitly use "__diag_ignore" to
specify the GCC version you are targeting.

Reported-by: kernel test robot <lkp@intel.com>
Closes: https://lore.kernel.org/oe-kbuild-all/202311031651.A7crZEur-lkp@intel.com/
Suggested-by: Arnd Bergmann <arnd@arndb.de>
Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>
Cc: Arnd Bergmann <arnd@arndb.de>
---
 include/linux/compiler-gcc.h | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

Comments

Alexei Starovoitov Nov. 9, 2023, 6:23 p.m. UTC | #1 
On Sun, Nov 5, 2023 at 7:18 PM Yafang Shao <laoar.shao@gmail.com> wrote:
>
> The kernel supports a minimum GCC version of 5.1.0 for building. However,
> the "__diag_ignore_all" directive only suppresses the
> "-Wmissing-prototypes" warning for GCC versions >= 8.0.0. As a result, when
> building the kernel with older GCC versions, warnings may be triggered. The
> example below illustrates the warnings reported by the kernel test robot
> using GCC 7.5.0:
>
>   compiler: gcc-7 (Ubuntu 7.5.0-6ubuntu2) 7.5.0
>   All warnings (new ones prefixed by >>):
>
>    kernel/bpf/helpers.c:1893:19: warning: no previous prototype for 'bpf_obj_new_impl' [-Wmissing-prototypes]
>     __bpf_kfunc void *bpf_obj_new_impl(u64 local_type_id__k, void *meta__ign)
>                       ^~~~~~~~~~~~~~~~
>    kernel/bpf/helpers.c:1907:19: warning: no previous prototype for 'bpf_percpu_obj_new_impl' [-Wmissing-prototypes]
>     __bpf_kfunc void *bpf_percpu_obj_new_impl(u64 local_type_id__k, void *meta__ign)
>    [...]
>
> To address this, we should also suppress the "-Wmissing-prototypes" warning
> for older GCC versions. "#pragma GCC diagnostic push" is supported as
> of GCC 4.6, and both "-Wmissing-prototypes" and "-Wmissing-declarations"
> are supported for all the GCC versions that we currently support.
> Therefore, it is reasonable to suppress these warnings for all supported
> GCC versions.
>
> With this adjustment, it's important to note that after implementing
> "__diag_ignore_all", it will effectively suppress warnings for all the
> supported GCC versions.
>
> In the future, if you wish to suppress warnings that are only supported on
> higher GCC versions, it is advisable to explicitly use "__diag_ignore" to
> specify the GCC version you are targeting.
>
> Reported-by: kernel test robot <lkp@intel.com>
> Closes: https://lore.kernel.org/oe-kbuild-all/202311031651.A7crZEur-lkp@intel.com/
> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> Cc: Arnd Bergmann <arnd@arndb.de>
> ---
>  include/linux/compiler-gcc.h | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> index 7af9e34..80918bd 100644
> --- a/include/linux/compiler-gcc.h
> +++ b/include/linux/compiler-gcc.h
> @@ -138,7 +138,7 @@
>  #endif
>
>  #define __diag_ignore_all(option, comment) \
> -       __diag_GCC(8, ignore, option)
> +       __diag(__diag_GCC_ignore option)

Arnd,
does this look good to you?

If so, pls ack.
Arnd Bergmann Nov. 10, 2023, 6:34 a.m. UTC | #2 
On Thu, Nov 9, 2023, at 19:23, Alexei Starovoitov wrote:
> On Sun, Nov 5, 2023 at 7:18 PM Yafang Shao <laoar.shao@gmail.com> wrote:
>> In the future, if you wish to suppress warnings that are only supported on
>> higher GCC versions, it is advisable to explicitly use "__diag_ignore" to
>> specify the GCC version you are targeting.
>>
>> Reported-by: kernel test robot <lkp@intel.com>
>> Closes: https://lore.kernel.org/oe-kbuild-all/202311031651.A7crZEur-lkp@intel.com/
>> Suggested-by: Arnd Bergmann <arnd@arndb.de>
>> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
>> Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>
>> Cc: Arnd Bergmann <arnd@arndb.de>
>> ---
>>  include/linux/compiler-gcc.h | 2 +-
>>  1 file changed, 1 insertion(+), 1 deletion(-)
>>
>> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
>> index 7af9e34..80918bd 100644
>> --- a/include/linux/compiler-gcc.h
>> +++ b/include/linux/compiler-gcc.h
>> @@ -138,7 +138,7 @@
>>  #endif
>>
>>  #define __diag_ignore_all(option, comment) \
>> -       __diag_GCC(8, ignore, option)
>> +       __diag(__diag_GCC_ignore option)
>
> Arnd,
> does this look good to you?

Yes, this is good. We could do the same thing for 
clang already, but it doesn't make a huge difference.

Acked-by: Arnd Bergmann <arnd@arndb.de>
Yafang Shao Nov. 10, 2023, 7:48 a.m. UTC | #3 
On Fri, Nov 10, 2023 at 2:35 PM Arnd Bergmann <arnd@arndb.de> wrote:
>
> On Thu, Nov 9, 2023, at 19:23, Alexei Starovoitov wrote:
> > On Sun, Nov 5, 2023 at 7:18 PM Yafang Shao <laoar.shao@gmail.com> wrote:
> >> In the future, if you wish to suppress warnings that are only supported on
> >> higher GCC versions, it is advisable to explicitly use "__diag_ignore" to
> >> specify the GCC version you are targeting.
> >>
> >> Reported-by: kernel test robot <lkp@intel.com>
> >> Closes: https://lore.kernel.org/oe-kbuild-all/202311031651.A7crZEur-lkp@intel.com/
> >> Suggested-by: Arnd Bergmann <arnd@arndb.de>
> >> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> >> Cc: Kumar Kartikeya Dwivedi <memxor@gmail.com>
> >> Cc: Arnd Bergmann <arnd@arndb.de>
> >> ---
> >>  include/linux/compiler-gcc.h | 2 +-
> >>  1 file changed, 1 insertion(+), 1 deletion(-)
> >>
> >> diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
> >> index 7af9e34..80918bd 100644
> >> --- a/include/linux/compiler-gcc.h
> >> +++ b/include/linux/compiler-gcc.h
> >> @@ -138,7 +138,7 @@
> >>  #endif
> >>
> >>  #define __diag_ignore_all(option, comment) \
> >> -       __diag_GCC(8, ignore, option)
> >> +       __diag(__diag_GCC_ignore option)
> >
> > Arnd,
> > does this look good to you?
>
> Yes, this is good. We could do the same thing for
> clang already, but it doesn't make a huge difference.

The Minimum Clang version is 11.0.0, so I think we don't have to
change compiler-clang.h.

>
> Acked-by: Arnd Bergmann <arnd@arndb.de>

Thanks for your review.
patchwork-bot+netdevbpf@kernel.org Nov. 10, 2023, 4 p.m. UTC | #4 
Hello:

This patch was applied to bpf/bpf-next.git (master)
by Alexei Starovoitov <ast@kernel.org>:

On Mon,  6 Nov 2023 03:18:02 +0000 you wrote:
> The kernel supports a minimum GCC version of 5.1.0 for building. However,
> the "__diag_ignore_all" directive only suppresses the
> "-Wmissing-prototypes" warning for GCC versions >= 8.0.0. As a result, when
> building the kernel with older GCC versions, warnings may be triggered. The
> example below illustrates the warnings reported by the kernel test robot
> using GCC 7.5.0:
> 
> [...]

Here is the summary with links:
  - [v2,bpf-next] compiler-gcc: Suppress -Wmissing-prototypes warning for all supported GCC
    https://git.kernel.org/bpf/bpf-next/c/689b097a06ba

You are awesome, thank you!
diff mbox series

Patch

diff --git a/include/linux/compiler-gcc.h b/include/linux/compiler-gcc.h
index 7af9e34..80918bd 100644
--- a/include/linux/compiler-gcc.h
+++ b/include/linux/compiler-gcc.h
@@ -138,7 +138,7 @@ 
 #endif
 
 #define __diag_ignore_all(option, comment) \
-	__diag_GCC(8, ignore, option)
+	__diag(__diag_GCC_ignore option)
 
 /*
  * Prior to 9.1, -Wno-alloc-size-larger-than (and therefore the "alloc_size"