| Message ID | 20190828055425.24765-2-yamada.masahiro@socionext.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
| Series | [1/2] kbuild: refactor scripts/Makefile.extrawarn | expand |
On Wed, Aug 28, 2019 at 02:54:25PM +0900, Masahiro Yamada wrote: > GCC and Clang have different policy for -Wunused-function; GCC does not > warn unused static inline functions at all whereas Clang does if they > are defined in source files instead of included headers although it has > been suppressed since commit abb2ea7dfd82 ("compiler, clang: suppress > warning for unused static inline functions"). > > We often miss to delete unused functions where 'static inline' is used > in *.c files since there is no tool to detect them. Unused code remains > until somebody notices. For example, commit 075ddd75680f ("regulator: > core: remove unused rdev_get_supply()"). > > Let's remove __maybe_unused from the inline macro to allow Clang to > start finding unused static inline functions. For now, we do this only > for W=1 build since it is not a good idea to sprinkle warnings for the > normal build. > > My initial attempt was to add -Wno-unused-function for no W=1 build > (https://lore.kernel.org/patchwork/patch/1120594/) > > Nathan Chancellor pointed out that would weaken Clang's checks since > we would no longer get -Wunused-function without W=1. It is true GCC > would detect unused static non-inline functions, but it would weaken > Clang as a standalone compiler at least. > > Here is a counter implementation. The current problem is, W=... only > controls compiler flags, which are globally effective. There is no way > to narrow the scope to only 'static inline' functions. > > This commit defines KBUILD_EXTRA_WARN[123] corresponding to W=[123]. > When KBUILD_EXTRA_WARN1 is defined, __maybe_unused is omitted from > the 'inline' macro. > > This makes the code a bit uglier, so personally I do not want to carry > this forever. If we can manage to fix most of the warnings, we can > drop this entirely, then enable -Wunused-function all the time. > > If you contribute to code clean-up, please run "make CC=clang W=1" > and check -Wunused-function warnings. You will find lots of unused > functions. > > Some of them are false-positives because the call-sites are disabled > by #ifdef. I do not like to abuse the inline keyword for suppressing > unused-function warnings because it is intended to be a hint for the > compiler optimization. I prefer #ifdef around the definition, or > __maybe_unused if #ifdef would make the code too ugly. > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> I can still see warnings from static unused functions and with W=1, I see plenty more. I agree that this is uglier because of the __inline_maybe_unused but I think this is better for regular developers. I will try to work on these unused-function warnings! Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> Tested-by: Nathan Chancellor <natechancellor@gmail.com>
On Wed, Aug 28, 2019 at 11:20 AM Nathan Chancellor <natechancellor@gmail.com> wrote: > > On Wed, Aug 28, 2019 at 02:54:25PM +0900, Masahiro Yamada wrote: > > GCC and Clang have different policy for -Wunused-function; GCC does not > > warn unused static inline functions at all whereas Clang does if they > > are defined in source files instead of included headers although it has > > been suppressed since commit abb2ea7dfd82 ("compiler, clang: suppress > > warning for unused static inline functions"). > > > > We often miss to delete unused functions where 'static inline' is used > > in *.c files since there is no tool to detect them. Unused code remains > > until somebody notices. For example, commit 075ddd75680f ("regulator: > > core: remove unused rdev_get_supply()"). > > > > Let's remove __maybe_unused from the inline macro to allow Clang to > > start finding unused static inline functions. For now, we do this only > > for W=1 build since it is not a good idea to sprinkle warnings for the > > normal build. > > > > My initial attempt was to add -Wno-unused-function for no W=1 build > > (https://lore.kernel.org/patchwork/patch/1120594/) > > > > Nathan Chancellor pointed out that would weaken Clang's checks since > > we would no longer get -Wunused-function without W=1. It is true GCC > > would detect unused static non-inline functions, but it would weaken > > Clang as a standalone compiler at least. Got it. No problem. > > > > Here is a counter implementation. The current problem is, W=... only > > controls compiler flags, which are globally effective. There is no way > > to narrow the scope to only 'static inline' functions. > > > > This commit defines KBUILD_EXTRA_WARN[123] corresponding to W=[123]. > > When KBUILD_EXTRA_WARN1 is defined, __maybe_unused is omitted from > > the 'inline' macro. > > > > This makes the code a bit uglier, so personally I do not want to carry > > this forever. If we can manage to fix most of the warnings, we can > > drop this entirely, then enable -Wunused-function all the time. How many warnings? > > > > If you contribute to code clean-up, please run "make CC=clang W=1" > > and check -Wunused-function warnings. You will find lots of unused > > functions. > > > > Some of them are false-positives because the call-sites are disabled > > by #ifdef. I do not like to abuse the inline keyword for suppressing > > unused-function warnings because it is intended to be a hint for the > > compiler optimization. I prefer #ifdef around the definition, or > > __maybe_unused if #ifdef would make the code too ugly. > > > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > > I can still see warnings from static unused functions and with W=1, I > see plenty more. I agree that this is uglier because of the > __inline_maybe_unused but I think this is better for regular developers. > I will try to work on these unused-function warnings! How many are we talking here? > > Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> > Tested-by: Nathan Chancellor <natechancellor@gmail.com> This is getting kind of messy. I was more ok when the goal seemed to be simplifying the definition of `inline`, but this is worse IMO.
On Wed, Aug 28, 2019 at 04:28:30PM -0700, Nick Desaulniers wrote: > On Wed, Aug 28, 2019 at 11:20 AM Nathan Chancellor > <natechancellor@gmail.com> wrote: > > > > On Wed, Aug 28, 2019 at 02:54:25PM +0900, Masahiro Yamada wrote: > > > GCC and Clang have different policy for -Wunused-function; GCC does not > > > warn unused static inline functions at all whereas Clang does if they > > > are defined in source files instead of included headers although it has > > > been suppressed since commit abb2ea7dfd82 ("compiler, clang: suppress > > > warning for unused static inline functions"). > > > > > > We often miss to delete unused functions where 'static inline' is used > > > in *.c files since there is no tool to detect them. Unused code remains > > > until somebody notices. For example, commit 075ddd75680f ("regulator: > > > core: remove unused rdev_get_supply()"). > > > > > > Let's remove __maybe_unused from the inline macro to allow Clang to > > > start finding unused static inline functions. For now, we do this only > > > for W=1 build since it is not a good idea to sprinkle warnings for the > > > normal build. > > > > > > My initial attempt was to add -Wno-unused-function for no W=1 build > > > (https://lore.kernel.org/patchwork/patch/1120594/) > > > > > > Nathan Chancellor pointed out that would weaken Clang's checks since > > > we would no longer get -Wunused-function without W=1. It is true GCC > > > would detect unused static non-inline functions, but it would weaken > > > Clang as a standalone compiler at least. > > Got it. No problem. > > > > > > > Here is a counter implementation. The current problem is, W=... only > > > controls compiler flags, which are globally effective. There is no way > > > to narrow the scope to only 'static inline' functions. > > > > > > This commit defines KBUILD_EXTRA_WARN[123] corresponding to W=[123]. > > > When KBUILD_EXTRA_WARN1 is defined, __maybe_unused is omitted from > > > the 'inline' macro. > > > > > > This makes the code a bit uglier, so personally I do not want to carry > > > this forever. If we can manage to fix most of the warnings, we can > > > drop this entirely, then enable -Wunused-function all the time. > > How many warnings? In an x86 defconfig build (one of the smallest builds we do), I see an additional 35 warnings that crop up: https://gist.github.com/003ba86ba60b4ac7e8109089d6cb1a5a > > > > > > If you contribute to code clean-up, please run "make CC=clang W=1" > > > and check -Wunused-function warnings. You will find lots of unused > > > functions. > > > > > > Some of them are false-positives because the call-sites are disabled > > > by #ifdef. I do not like to abuse the inline keyword for suppressing > > > unused-function warnings because it is intended to be a hint for the > > > compiler optimization. I prefer #ifdef around the definition, or > > > __maybe_unused if #ifdef would make the code too ugly. > > > > > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > > > > I can still see warnings from static unused functions and with W=1, I > > see plenty more. I agree that this is uglier because of the > > __inline_maybe_unused but I think this is better for regular developers. > > I will try to work on these unused-function warnings! > > How many are we talking here? > > > > > Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> > > Tested-by: Nathan Chancellor <natechancellor@gmail.com> > > This is getting kind of messy. I was more ok when the goal seemed to > be simplifying the definition of `inline`, but this is worse IMO. I guess if you want, we can just go back to v1 and have all unused function warnings hidden by default with clang. Fixing these warnings will take a significant amount of time given there will probably be a few hundred so I don't think having this warning hidden behind W=1 for that long is a good thing. Cheers, Nathan
On Thu, Aug 29, 2019 at 1:28 AM 'Nick Desaulniers' via Clang Built Linux <clang-built-linux@googlegroups.com> wrote: [...] > > > > > > Here is a counter implementation. The current problem is, W=... only > > > controls compiler flags, which are globally effective. There is no way > > > to narrow the scope to only 'static inline' functions. > > > > > > This commit defines KBUILD_EXTRA_WARN[123] corresponding to W=[123]. > > > When KBUILD_EXTRA_WARN1 is defined, __maybe_unused is omitted from > > > the 'inline' macro. > > > > > > This makes the code a bit uglier, so personally I do not want to carry > > > this forever. If we can manage to fix most of the warnings, we can > > > drop this entirely, then enable -Wunused-function all the time. > > How many warnings? > I tried or adapted this 2-2 patch with v2 of 1-2 patch which is in kbuild.git#kbuild (see below [1]). $ grep warning: build-log.txt | grep '\[-Wunused-function]' | wc -l 214 $ grep warning: build-log.txt | grep '\[-Wunused-function]' | sort arch/x86/kernel/apic/io_apic.c:162:19: warning: unused function 'mp_init_irq_at_boot' [-Wunused-function] arch/x86/kernel/cpu/common.c:298:19: warning: unused function 'flag_is_changeable_p' [-Wunused-function] arch/x86/kvm/lapic.c:302:19: warning: unused function 'apic_lvt_vector' [-Wunused-function] arch/x86/xen/p2m.c:137:24: warning: unused function 'p2m_index' [-Wunused-function] block/blk-zoned.c:23:24: warning: unused function 'blk_zone_start' [-Wunused-function] block/partitions/mac.c:23:20: warning: unused function 'mac_fix_string' [-Wunused-function] drivers/acpi/ec.c:2047:20: warning: unused function 'acpi_ec_query_exit' [-Wunused-function] drivers/atm/horizon.c:465:20: warning: unused function 'dump_regs' [-Wunused-function] drivers/atm/horizon.c:479:20: warning: unused function 'dump_framer' [-Wunused-function] drivers/atm/idt77252.c:1786:1: warning: unused function 'idt77252_fbq_level' [-Wunused-function] drivers/cpufreq/intel_pstate.c:77:23: warning: unused function 'percent_fp' [-Wunused-function] drivers/cpufreq/intel_pstate.c:92:23: warning: unused function 'percent_ext_fp' [-Wunused-function] drivers/crypto/chelsio/chcr_algo.c:129:19: warning: unused function 'is_ofld_imm' [-Wunused-function] drivers/crypto/qat/qat_common/qat_asym_algs.c:252:34: warning: unused function 'qat_dh_get_params' [-Wunused-function] drivers/dma/ioat/dca.c:44:19: warning: unused function 'dca2_tag_map_valid' [-Wunused-function] drivers/edac/i5100_edac.c:247:19: warning: unused function 'i5100_nrecmema_dm_buf_id' [-Wunused-function] drivers/gpu/drm/drm_mm.c:155:1: warning: unused function 'drm_mm_interval_tree_insert' [-Wunused-function] drivers/gpu/drm/drm_mm.c:155:1: warning: unused function 'drm_mm_interval_tree_iter_next' [-Wunused-function] drivers/gpu/drm/drm_mm.c:294:19: warning: unused function 'rb_hole_size' [-Wunused-function] drivers/gpu/drm/gma500/psb_drv.c:400:20: warning: unused function 'get_brightness' [-Wunused-function] drivers/gpu/drm/gma500/psb_irq.c:49:1: warning: unused function 'mid_pipe_vsync' [-Wunused-function] drivers/gpu/drm/i915/display/intel_hdmi.c:1696:26: warning: unused function 'intel_hdmi_hdcp2_protocol' [-Wunused-function] drivers/gpu/drm/i915/i915_sw_fence.c:105:20: warning: unused function 'debug_fence_free' [-Wunused-function] drivers/gpu/drm/i915/i915_sw_fence.c:84:20: warning: unused function 'debug_fence_init_onstack' [-Wunused-function] drivers/gpu/drm/i915/intel_guc_submission.c:1117:20: warning: unused function 'ctx_save_restore_disabled' [-Wunused-function] drivers/gpu/drm/vmwgfx/vmwgfx_overlay.c:58:35: warning: unused function 'vmw_overlay' [-Wunused-function] drivers/hv/ring_buffer.c:89:1: warning: unused function 'hv_set_next_read_location' [-Wunused-function] drivers/hwmon/nct6683.c:485:19: warning: unused function 'in_to_reg' [-Wunused-function] drivers/hwmon/sis5595.c:158:18: warning: unused function 'DIV_TO_REG' [-Wunused-function] drivers/hwmon/vt1211.c:198:20: warning: unused function 'superio_outb' [-Wunused-function] drivers/infiniband/core/cm.c:1528:19: warning: unused function 'cm_is_active_peer' [-Wunused-function] drivers/infiniband/core/device.c:2747:1: warning: unused function '__chk_RDMA_NL_LS' [-Wunused-function] drivers/infiniband/core/iwcm.c:1208:1: warning: unused function '__chk_RDMA_NL_IWCM' [-Wunused-function] drivers/infiniband/core/nldev.c:2105:1: warning: unused function '__chk_RDMA_NL_NLDEV' [-Wunused-function] drivers/infiniband/hw/qib/qib_iba7322.c:803:19: warning: unused function 'qib_read_ureg' [-Wunused-function] drivers/infiniband/sw/rdmavt/vt.c:287:36: warning: unused function 'to_iucontext' [-Wunused-function] drivers/isdn/hardware/mISDN/hfcmulti.c:667:1: warning: unused function 'vpm_read_address' [-Wunused-function] drivers/leds/leds-pca955x.c:140:19: warning: unused function 'pca95xx_num_led_regs' [-Wunused-function] drivers/md/raid0.c:444:19: warning: unused function 'is_io_in_chunk_boundary' [-Wunused-function] drivers/media/dvb-frontends/drxk_hard.c:159:19: warning: unused function 'MulDiv32' [-Wunused-function] drivers/media/dvb-frontends/stb6100.c:113:20: warning: unused function 'stb6100_normalise_regs' [-Wunused-function] drivers/media/i2c/cs3308.c:30:19: warning: unused function 'cs3308_read' [-Wunused-function] drivers/media/i2c/cx25840/cx25840-ir.c:139:19: warning: unused function 'ns_to_clock_divider' [-Wunused-function] drivers/media/i2c/cx25840/cx25840-ir.c:145:28: warning: unused function 'clock_divider_to_ns' [-Wunused-function] drivers/media/i2c/cx25840/cx25840-ir.c:163:19: warning: unused function 'freq_to_clock_divider' [-Wunused-function] drivers/media/mc/mc-entity.c:17:27: warning: unused function 'gobj_type' [-Wunused-function] drivers/media/pci/cx18/cx18-alsa-main.c:56:23: warning: unused function 'p_to_snd_cx18_card' [-Wunused-function] drivers/media/pci/cx23885/cx23888-ir.c:178:19: warning: unused function 'ns_to_clock_divider' [-Wunused-function] drivers/media/pci/cx23885/cx23888-ir.c:184:28: warning: unused function 'clock_divider_to_ns' [-Wunused-function] drivers/media/pci/cx23885/cx23888-ir.c:202:19: warning: unused function 'freq_to_clock_divider' [-Wunused-function] drivers/media/pci/ivtv/ivtv-alsa-main.c:53:23: warning: unused function 'p_to_snd_ivtv_card' [-Wunused-function] drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c:394:19: warning: unused function 'vop_interlaced' [-Wunused-function] drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c:399:18: warning: unused function 'vop_channel' [-Wunused-function] drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c:414:18: warning: unused function 'vop_hsize' [-Wunused-function] drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c:419:18: warning: unused function 'vop_vsize' [-Wunused-function] drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c:439:19: warning: unused function 'vop_sec' [-Wunused-function] drivers/media/pci/solo6x10/solo6x10-v4l2-enc.c:444:19: warning: unused function 'vop_usec' [-Wunused-function] drivers/media/rc/fintek-cir.c:55:20: warning: unused function 'fintek_clear_reg_bit' [-Wunused-function] drivers/media/rc/nuvoton-cir.c:78:20: warning: unused function 'nvt_clear_reg_bit' [-Wunused-function] drivers/media/usb/au0828/au0828-i2c.c:26:19: warning: unused function 'i2c_slave_did_write_ack' [-Wunused-function] drivers/media/usb/usbvision/usbvision-video.c:145:37: warning: unused function 'cd_to_usbvision' [-Wunused-function] drivers/misc/hpilo.c:396:19: warning: unused function 'is_device_reset' [-Wunused-function] drivers/mmc/host/sdricoh_cs.c:104:28: warning: unused function 'sdricoh_readw' [-Wunused-function] drivers/net/ethernet/atheros/atl1c/atl1c_main.c:184:20: warning: unused function 'atl1c_irq_reset' [-Wunused-function] drivers/net/ethernet/broadcom/b44.c:201:20: warning: unused function '__b44_cam_read' [-Wunused-function] drivers/net/ethernet/broadcom/bnx2x/bnx2x_sriov.c:334:20: warning: unused function 'bnx2x_vf_vlan_credit' [-Wunused-function] drivers/net/ethernet/cavium/liquidio/request_manager.c:43:19: warning: unused function 'IQ_INSTR_MODE_64B' [-Wunused-function] drivers/net/ethernet/chelsio/cxgb3/sge.c:167:32: warning: unused function 'fl_to_qset' [-Wunused-function] drivers/net/ethernet/chelsio/cxgb4/sge.c:857:28: warning: unused function 'calc_tx_descs' [-Wunused-function] drivers/net/ethernet/intel/ixgbe/ixgbe_main.c:2952:20: warning: unused function 'ixgbe_irq_disable_queues' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:1546:20: warning: unused function 'hw_ena_intr_bit' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2120:19: warning: unused function 'port_chk_broad_storm' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2278:20: warning: unused function 'port_cfg_force_flow_ctrl' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2284:19: warning: unused function 'port_chk_back_pressure' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2290:19: warning: unused function 'port_chk_force_flow_ctrl' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2298:20: warning: unused function 'port_cfg_rx' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2304:20: warning: unused function 'port_cfg_tx' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2315:20: warning: unused function 'sw_flush_dyn_mac_table' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2326:20: warning: unused function 'port_cfg_ins_tag' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2332:20: warning: unused function 'port_cfg_rmv_tag' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2338:19: warning: unused function 'port_chk_ins_tag' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2344:19: warning: unused function 'port_chk_rmv_tag' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2350:20: warning: unused function 'port_cfg_dis_non_vid' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2356:20: warning: unused function 'port_cfg_in_filter' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2362:19: warning: unused function 'port_chk_dis_non_vid' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2368:19: warning: unused function 'port_chk_in_filter' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2411:20: warning: unused function 'sw_cfg_unk_def_deliver' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2417:19: warning: unused function 'sw_cfg_chk_unk_def_deliver' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2423:20: warning: unused function 'sw_cfg_unk_def_port' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2428:19: warning: unused function 'sw_chk_unk_def_port' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2459:19: warning: unused function 'port_chk_diffserv' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2465:19: warning: unused function 'port_chk_802_1p' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2471:19: warning: unused function 'port_chk_replace_vid' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2477:19: warning: unused function 'port_chk_prio' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2689:20: warning: unused function 'sw_get_addr' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2906:20: warning: unused function 'hw_r_phy_link_stat' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2911:20: warning: unused function 'hw_r_phy_auto_neg' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2916:20: warning: unused function 'hw_w_phy_auto_neg' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2921:20: warning: unused function 'hw_r_phy_rem_cap' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2926:20: warning: unused function 'hw_r_phy_crossover' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2931:20: warning: unused function 'hw_w_phy_crossover' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2936:20: warning: unused function 'hw_r_phy_polarity' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2941:20: warning: unused function 'hw_w_phy_polarity' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2946:20: warning: unused function 'hw_r_phy_link_md' [-Wunused-function] drivers/net/ethernet/micrel/ksz884x.c:2951:20: warning: unused function 'hw_w_phy_link_md' [-Wunused-function] drivers/net/ethernet/myricom/myri10ge/myri10ge.c:1177:20: warning: unused function 'myri10ge_vlan_ip_csum' [-Wunused-function] drivers/net/ethernet/sun/cassini.c:240:20: warning: unused function 'cas_lock_all' [-Wunused-function] drivers/net/ethernet/sun/cassini.c:269:20: warning: unused function 'cas_unlock_all' [-Wunused-function] drivers/net/ethernet/tehuti/tehuti.c:1368:19: warning: unused function 'bdx_tx_db_size' [-Wunused-function] drivers/net/usb/plusb.c:67:1: warning: unused function 'pl_clear_QuickLink_features' [-Wunused-function] drivers/net/usb/sierra_net.c:357:19: warning: unused function 'sierra_net_is_valid_addrlen' [-Wunused-function] drivers/net/wireless/ath/ath10k/ce.c:127:1: warning: unused function 'ath10k_get_ring_byte' [-Wunused-function] drivers/net/wireless/ath/ath10k/ce.c:212:1: warning: unused function 'ath10k_ce_shadow_dest_ring_write_index_set' [-Wunused-function] drivers/net/wireless/ath/ath10k/ce.c:449:20: warning: unused function 'ath10k_ce_error_intr_enable' [-Wunused-function] drivers/net/wireless/broadcom/b43legacy/dma.c:130:19: warning: unused function 'prev_slot' [-Wunused-function] drivers/net/wireless/broadcom/b43legacy/dma.c:217:19: warning: unused function 'txring_to_priority' [-Wunused-function] drivers/net/wireless/broadcom/b43legacy/radio.c:1713:5: warning: unused function 'freq_r3A_value' [-Wunused-function] drivers/net/wireless/intel/ipw2x00/ipw2200.c:3010:19: warning: unused function 'ipw_alive' [-Wunused-function] drivers/net/wireless/intel/ipw2x00/ipw2200.c:381:19: warning: unused function '_ipw_read16' [-Wunused-function] drivers/net/wireless/intel/iwlegacy/3945.c:226:1: warning: unused function 'il3945_get_tx_fail_reason' [-Wunused-function] drivers/net/wireless/intel/iwlwifi/mvm/sta.c:1370:18: warning: unused function 'iwl_mvm_tid_to_ac_queue' [-Wunused-function] drivers/net/wireless/realtek/rtw88/pci.c:81:21: warning: unused function 'rtw_pci_get_tx_desc' [-Wunused-function] drivers/nvme/target/fc.c:151:1: warning: unused function 'nvmet_fc_iodnum' [-Wunused-function] drivers/nvme/target/fc.c:157:1: warning: unused function 'nvmet_fc_fodnum' [-Wunused-function] drivers/pci/hotplug/shpchp_hpc.c:177:20: warning: unused function 'shpc_writeb' [-Wunused-function] drivers/pcmcia/yenta_socket.c:147:18: warning: unused function 'exca_readw' [-Wunused-function] drivers/scsi/aacraid/aachba.c:1880:19: warning: unused function 'aac_get_safw_phys_device_type' [-Wunused-function] drivers/scsi/cxgbi/libcxgbi.c:2287:19: warning: unused function 'csk_print_port' [-Wunused-function] drivers/scsi/cxgbi/libcxgbi.c:2298:19: warning: unused function 'csk_print_ip' [-Wunused-function] drivers/scsi/myrb.c:2557:20: warning: unused function 'DAC960_LA_gen_intr' [-Wunused-function] drivers/scsi/myrb.c:2591:20: warning: unused function 'DAC960_LA_ack_mem_mbox_intr' [-Wunused-function] drivers/scsi/myrb.c:2609:20: warning: unused function 'DAC960_LA_mem_mbox_status_available' [-Wunused-function] drivers/scsi/myrb.c:2632:20: warning: unused function 'DAC960_LA_intr_enabled' [-Wunused-function] drivers/scsi/myrb.c:2661:29: warning: unused function 'DAC960_LA_read_status_cmd_ident' [-Wunused-function] drivers/scsi/myrb.c:2834:20: warning: unused function 'DAC960_PG_gen_intr' [-Wunused-function] drivers/scsi/myrb.c:2868:20: warning: unused function 'DAC960_PG_ack_mem_mbox_intr' [-Wunused-function] drivers/scsi/myrb.c:2886:20: warning: unused function 'DAC960_PG_mem_mbox_status_available' [-Wunused-function] drivers/scsi/myrb.c:2908:20: warning: unused function 'DAC960_PG_intr_enabled' [-Wunused-function] drivers/scsi/myrb.c:2938:1: warning: unused function 'DAC960_PG_read_status_cmd_ident' [-Wunused-function] drivers/scsi/myrb.c:3112:20: warning: unused function 'DAC960_PD_gen_intr' [-Wunused-function] drivers/scsi/myrb.c:3158:20: warning: unused function 'DAC960_PD_intr_enabled' [-Wunused-function] drivers/scsi/myrs.c:2416:20: warning: unused function 'DAC960_GEM_gen_intr' [-Wunused-function] drivers/scsi/myrs.c:2460:20: warning: unused function 'DAC960_GEM_ack_mem_mbox_intr' [-Wunused-function] drivers/scsi/myrs.c:2483:20: warning: unused function 'DAC960_GEM_mem_mbox_status_available' [-Wunused-function] drivers/scsi/myrs.c:2505:20: warning: unused function 'DAC960_GEM_intr_enabled' [-Wunused-function] drivers/scsi/myrs.c:2533:30: warning: unused function 'DAC960_GEM_read_cmd_ident' [-Wunused-function] drivers/scsi/myrs.c:2682:20: warning: unused function 'DAC960_BA_gen_intr' [-Wunused-function] drivers/scsi/myrs.c:2718:20: warning: unused function 'DAC960_BA_ack_mem_mbox_intr' [-Wunused-function] drivers/scsi/myrs.c:2737:20: warning: unused function 'DAC960_BA_mem_mbox_status_available' [-Wunused-function] drivers/scsi/myrs.c:2755:20: warning: unused function 'DAC960_BA_intr_enabled' [-Wunused-function] drivers/scsi/myrs.c:2782:30: warning: unused function 'DAC960_BA_read_cmd_ident' [-Wunused-function] drivers/scsi/myrs.c:2932:20: warning: unused function 'DAC960_LP_gen_intr' [-Wunused-function] drivers/scsi/myrs.c:2968:20: warning: unused function 'DAC960_LP_ack_mem_mbox_intr' [-Wunused-function] drivers/scsi/myrs.c:2987:20: warning: unused function 'DAC960_LP_mem_mbox_status_available' [-Wunused-function] drivers/scsi/myrs.c:3005:20: warning: unused function 'DAC960_LP_intr_enabled' [-Wunused-function] drivers/scsi/myrs.c:3031:30: warning: unused function 'DAC960_LP_read_cmd_ident' [-Wunused-function] drivers/scsi/qla2xxx/qla_nx.c:384:1: warning: unused function 'qla82xx_pci_set_crbwindow' [-Wunused-function] drivers/scsi/qla4xxx/ql4_nx.c:3654:1: warning: unused function 'flash_data_addr' [-Wunused-function] drivers/staging/comedi/drivers/cb_pcidas64.c:232:19: warning: unused function 'analog_trig_low_threshold_bits' [-Wunused-function] drivers/staging/comedi/drivers/cb_pcidas64.c:383:28: warning: unused function 'dma_chain_flag_bits' [-Wunused-function] drivers/staging/isdn/gigaset/bas-gigaset.c:241:21: warning: unused function 'usb_pipetype_str' [-Wunused-function] drivers/staging/rtl8192u/ieee80211/ieee80211_rx.c:2072:18: warning: unused function 'ieee80211_SignalStrengthTranslate' [-Wunused-function] drivers/staging/rts5208/xd.c:34:19: warning: unused function 'xd_check_err_code' [-Wunused-function] drivers/tty/isicom.c:369:19: warning: unused function '__isicom_paranoia_check' [-Wunused-function] drivers/usb/host/sl811-hcd.c:588:18: warning: unused function 'checkdone' [-Wunused-function] drivers/usb/host/u132-hcd.c:220:28: warning: unused function 'udev_to_u132' [-Wunused-function] drivers/usb/serial/quatech2.c:179:19: warning: unused function 'qt2_setdevice' [-Wunused-function] drivers/usb/typec/tps6598x.c:158:19: warning: unused function 'tps6598x_write16' [-Wunused-function] drivers/usb/typec/tps6598x.c:163:19: warning: unused function 'tps6598x_write32' [-Wunused-function] drivers/vhost/vhost.c:52:1: warning: unused function 'vhost_umem_interval_tree_iter_next' [-Wunused-function] drivers/video/fbdev/arkfb.c:321:18: warning: unused function 'dac_read_reg' [-Wunused-function] drivers/video/fbdev/arkfb.c:328:20: warning: unused function 'dac_read_regs' [-Wunused-function] drivers/video/fbdev/aty/aty128fb.c:548:18: warning: unused function '_aty_ld_8' [-Wunused-function] drivers/video/fbdev/neofb.c:145:20: warning: unused function 'write_le32' [-Wunused-function] drivers/video/fbdev/tridentfb.c:1127:20: warning: unused function 'shadowmode_off' [-Wunused-function] drivers/watchdog/it87_wdt.c:152:20: warning: unused function 'superio_outw' [-Wunused-function] fs/btrfs/extent-tree.c:2723:19: warning: unused function 'heads_to_leaves' [-Wunused-function] fs/cifs/dfs_cache.c:317:20: warning: unused function 'is_sysvol_or_netlogon' [-Wunused-function] fs/dlm/lock.c:238:19: warning: unused function 'is_granted' [-Wunused-function] fs/lockd/xdr.c:109:1: warning: unused function 'nlm_encode_oh' [-Wunused-function] fs/nfsd/nfs4state.c:6034:1: warning: unused function 'end_offset' [-Wunused-function] fs/ocfs2/dlm/dlmrecovery.c:129:20: warning: unused function 'dlm_reset_recovery' [-Wunused-function] fs/xfs/xfs_sysfs.c:72:1: warning: unused function 'to_mp' [-Wunused-function] kernel/locking/rwsem.c:219:20: warning: unused function 'is_rwsem_reader_owned' [-Wunused-function] kernel/locking/rwsem.c:284:35: warning: unused function 'rwsem_owner' [-Wunused-function] kernel/power/snapshot.c:1260:21: warning: unused function 'saveable_highmem_page' [-Wunused-function] kernel/sched/cputime.c:255:19: warning: unused function 'account_other_time' [-Wunused-function] kernel/sched/fair.c:4383:19: warning: unused function 'cfs_rq_clock_task' [-Wunused-function] kernel/trace/trace_events_filter.c:1563:1: warning: unused function 'event_set_no_set_filter_flag' [-Wunused-function] kernel/trace/trace_events_filter.c:1569:1: warning: unused function 'event_clear_no_set_filter_flag' [-Wunused-function] kernel/trace/trace_events_filter.c:1575:1: warning: unused function 'event_no_set_filter_flag' [-Wunused-function] kernel/trace/trace_kprobe.c:96:38: warning: unused function 'trace_kprobe_offset' [-Wunused-function] lib/zlib_inflate/inffast.c:31:1: warning: unused function 'get_unaligned16' [-Wunused-function] mm/memcontrol.c:4661:20: warning: unused function 'mem_cgroup_id_get' [-Wunused-function] mm/slub.c:1401:29: warning: unused function 'slab_free_hook' [-Wunused-function] mm/slub.c:2007:28: warning: unused function 'tid_to_cpu' [-Wunused-function] mm/slub.c:2012:29: warning: unused function 'tid_to_event' [-Wunused-function] mm/zsmalloc.c:479:20: warning: unused function 'set_zspage_inuse' [-Wunused-function] net/bluetooth/6lowpan.c:105:35: warning: unused function 'peer_lookup_ba' [-Wunused-function] net/bluetooth/6lowpan.c:912:20: warning: unused function 'bdaddr_type' [-Wunused-function] net/ipv6/exthdrs.c:712:33: warning: unused function 'ipv6_skb_idev' [-Wunused-function] net/ipv6/ip6_gre.c:846:20: warning: unused function 'ip6gre_tnl_addr_conflict' [-Wunused-function] net/sched/sch_choke.c:145:20: warning: unused function 'choke_set_classid' [-Wunused-function] net/sunrpc/svcauth_unix.c:301:30: warning: unused function 'ip_map_lookup' [-Wunused-function] net/sunrpc/svcauth_unix.c:330:19: warning: unused function 'ip_map_update' [-Wunused-function] security/apparmor/file.c:159:20: warning: unused function 'is_deleted' [-Wunused-function] security/apparmor/label.c:1230:20: warning: unused function 'label_is_visible' [-Wunused-function] sound/drivers/portman2x4.c:186:18: warning: unused function 'portman_read_command' [-Wunused-function] sound/drivers/portman2x4.c:196:18: warning: unused function 'portman_read_data' [-Wunused-function] sound/pci/asihpi/asihpi.c:261:19: warning: unused function 'hpi_stream_group_get_map' [-Wunused-function] sound/pci/azt3328.c:368:1: warning: unused function 'snd_azf3328_codec_outl' [-Wunused-function] sound/pci/rme9652/hdspm.c:6154:19: warning: unused function 'copy_u32_le' [-Wunused-function] sound/pci/trident/trident_memory.c:109:21: warning: unused function 'offset_ptr' [-Wunused-function] sound/pci/ymfpci/ymfpci_main.c:34:18: warning: unused function 'snd_ymfpci_readb' [-Wunused-function] Hope this helps. - Sedat - [1] https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git/commit/?h=kbuild&id=025960c034eacc433afd366085077991f8ed6e4e
Just as a sidenote:
From [PATCH v2] kbuild: enable unused-function warnings for W= build with Clang:
"Per the documentation [1], -Wno-unused-function will also disable
-Wunneeded-internal-declaration, which can help find bugs like
commit 8289c4b6f2e5 ("platform/x86: mlx-platform: Properly use
mlxplat_mlxcpld_msn201x_items"). (pointed out by Nathan Chancellor)
I added -Wunneeded-internal-declaration to address it.
If you contribute to code clean-up, please run "make CC=clang W=1"
and check -Wunused-function warnings. You will find lots of unused
functions."
Isn't that missing in your double?
- Sedat -
[1] https://lkml.org/lkml/2019/8/27/729
On Thu, Aug 29, 2019 at 9:05 AM Nathan Chancellor <natechancellor@gmail.com> wrote: > > On Wed, Aug 28, 2019 at 04:28:30PM -0700, Nick Desaulniers wrote: > > On Wed, Aug 28, 2019 at 11:20 AM Nathan Chancellor > > <natechancellor@gmail.com> wrote: > > > > > > On Wed, Aug 28, 2019 at 02:54:25PM +0900, Masahiro Yamada wrote: > > > > GCC and Clang have different policy for -Wunused-function; GCC does not > > > > warn unused static inline functions at all whereas Clang does if they > > > > are defined in source files instead of included headers although it has > > > > been suppressed since commit abb2ea7dfd82 ("compiler, clang: suppress > > > > warning for unused static inline functions"). > > > > > > > > We often miss to delete unused functions where 'static inline' is used > > > > in *.c files since there is no tool to detect them. Unused code remains > > > > until somebody notices. For example, commit 075ddd75680f ("regulator: > > > > core: remove unused rdev_get_supply()"). > > > > > > > > Let's remove __maybe_unused from the inline macro to allow Clang to > > > > start finding unused static inline functions. For now, we do this only > > > > for W=1 build since it is not a good idea to sprinkle warnings for the > > > > normal build. > > > > > > > > My initial attempt was to add -Wno-unused-function for no W=1 build > > > > (https://lore.kernel.org/patchwork/patch/1120594/) > > > > > > > > Nathan Chancellor pointed out that would weaken Clang's checks since > > > > we would no longer get -Wunused-function without W=1. It is true GCC > > > > would detect unused static non-inline functions, but it would weaken > > > > Clang as a standalone compiler at least. > > > > Got it. No problem. > > > > > > > > > > Here is a counter implementation. The current problem is, W=... only > > > > controls compiler flags, which are globally effective. There is no way > > > > to narrow the scope to only 'static inline' functions. > > > > > > > > This commit defines KBUILD_EXTRA_WARN[123] corresponding to W=[123]. > > > > When KBUILD_EXTRA_WARN1 is defined, __maybe_unused is omitted from > > > > the 'inline' macro. > > > > > > > > This makes the code a bit uglier, so personally I do not want to carry > > > > this forever. If we can manage to fix most of the warnings, we can > > > > drop this entirely, then enable -Wunused-function all the time. > > > > How many warnings? > > In an x86 defconfig build (one of the smallest builds we do), I see an > additional 35 warnings that crop up: > > https://gist.github.com/003ba86ba60b4ac7e8109089d6cb1a5a > > > > > > > > > If you contribute to code clean-up, please run "make CC=clang W=1" > > > > and check -Wunused-function warnings. You will find lots of unused > > > > functions. > > > > > > > > Some of them are false-positives because the call-sites are disabled > > > > by #ifdef. I do not like to abuse the inline keyword for suppressing > > > > unused-function warnings because it is intended to be a hint for the > > > > compiler optimization. I prefer #ifdef around the definition, or > > > > __maybe_unused if #ifdef would make the code too ugly. > > > > > > > > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> > > > > > > I can still see warnings from static unused functions and with W=1, I > > > see plenty more. I agree that this is uglier because of the > > > __inline_maybe_unused but I think this is better for regular developers. > > > I will try to work on these unused-function warnings! > > > > How many are we talking here? > > > > > > > > Reviewed-by: Nathan Chancellor <natechancellor@gmail.com> > > > Tested-by: Nathan Chancellor <natechancellor@gmail.com> > > > > This is getting kind of messy. I was more ok when the goal seemed to > > be simplifying the definition of `inline`, but this is worse IMO. > > I guess if you want, we can just go back to v1 and have all unused > function warnings hidden by default with clang. Fixing these warnings > will take a significant amount of time given there will probably be a > few hundred so I don't think having this warning hidden behind W=1 for > that long is a good thing. > > Cheers, > Nathan I slightly prefer this version. Either way we go, I want to fix -Wunused-function warnings, then revert this patch as soon as possible. -- Best Regards Masahiro Yamada
On Fri, Aug 30, 2019 at 6:52 PM Sedat Dilek <sedat.dilek@gmail.com> wrote: > > Just as a sidenote: > > From [PATCH v2] kbuild: enable unused-function warnings for W= build with Clang: > > "Per the documentation [1], -Wno-unused-function will also disable > -Wunneeded-internal-declaration, which can help find bugs like > commit 8289c4b6f2e5 ("platform/x86: mlx-platform: Properly use > mlxplat_mlxcpld_msn201x_items"). (pointed out by Nathan Chancellor) > I added -Wunneeded-internal-declaration to address it. > > If you contribute to code clean-up, please run "make CC=clang W=1" > and check -Wunused-function warnings. You will find lots of unused > functions." This information is unrelated to this version, so I dropped it. > Isn't that missing in your double? > > - Sedat - > > [1] https://lkml.org/lkml/2019/8/27/729
diff --git a/include/linux/compiler_types.h b/include/linux/compiler_types.h index 599c27b56c29..b056a40116da 100644 --- a/include/linux/compiler_types.h +++ b/include/linux/compiler_types.h @@ -130,10 +130,6 @@ struct ftrace_likely_data { /* * Force always-inline if the user requests it so via the .config. - * GCC does not warn about unused static inline functions for - * -Wunused-function. This turns out to avoid the need for complex #ifdef - * directives. Suppress the warning in clang as well by using "unused" - * function attribute, which is redundant but not harmful for gcc. * Prefer gnu_inline, so that extern inline functions do not emit an * externally visible function. This makes extern inline behave as per gnu89 * semantics rather than c99. This prevents multiple symbol definition errors @@ -144,15 +140,27 @@ struct ftrace_likely_data { */ #if !defined(CONFIG_OPTIMIZE_INLINING) #define inline inline __attribute__((__always_inline__)) __gnu_inline \ - __maybe_unused notrace + __inline_maybe_unused notrace #else #define inline inline __gnu_inline \ - __maybe_unused notrace + __inline_maybe_unused notrace #endif #define __inline__ inline #define __inline inline +/* + * GCC does not warn about unused static inline functions for -Wunused-function. + * Suppress the warning in clang as well by using __maybe_unused, but enable it + * for W=1 build. This will allow clang to find unused functions. Remove the + * __inline_maybe_unused entirely after fixing most of -Wunused-function warnings. + */ +#ifdef KBUILD_EXTRA_WARN1 +#define __inline_maybe_unused +#else +#define __inline_maybe_unused __maybe_unused +#endif + /* * Rather then using noinline to prevent stack consumption, use * noinline_for_stack instead. For documentation reasons. diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn index 1fa53968e292..3af1770497fd 100644 --- a/scripts/Makefile.extrawarn +++ b/scripts/Makefile.extrawarn @@ -28,6 +28,8 @@ KBUILD_CFLAGS += $(call cc-option, -Wstringop-truncation) KBUILD_CFLAGS += -Wno-missing-field-initializers KBUILD_CFLAGS += -Wno-sign-compare +KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1 + else # W=1 also stops suppressing some warnings @@ -56,6 +58,8 @@ KBUILD_CFLAGS += -Wsign-compare KBUILD_CFLAGS += $(call cc-option, -Wmaybe-uninitialized) KBUILD_CFLAGS += $(call cc-option, -Wunused-macros) +KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN2 + endif # @@ -73,4 +77,6 @@ KBUILD_CFLAGS += -Wredundant-decls KBUILD_CFLAGS += -Wswitch-default KBUILD_CFLAGS += $(call cc-option, -Wpacked-bitfield-compat) +KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN3 + endif
GCC and Clang have different policy for -Wunused-function; GCC does not warn unused static inline functions at all whereas Clang does if they are defined in source files instead of included headers although it has been suppressed since commit abb2ea7dfd82 ("compiler, clang: suppress warning for unused static inline functions"). We often miss to delete unused functions where 'static inline' is used in *.c files since there is no tool to detect them. Unused code remains until somebody notices. For example, commit 075ddd75680f ("regulator: core: remove unused rdev_get_supply()"). Let's remove __maybe_unused from the inline macro to allow Clang to start finding unused static inline functions. For now, we do this only for W=1 build since it is not a good idea to sprinkle warnings for the normal build. My initial attempt was to add -Wno-unused-function for no W=1 build (https://lore.kernel.org/patchwork/patch/1120594/) Nathan Chancellor pointed out that would weaken Clang's checks since we would no longer get -Wunused-function without W=1. It is true GCC would detect unused static non-inline functions, but it would weaken Clang as a standalone compiler at least. Here is a counter implementation. The current problem is, W=... only controls compiler flags, which are globally effective. There is no way to narrow the scope to only 'static inline' functions. This commit defines KBUILD_EXTRA_WARN[123] corresponding to W=[123]. When KBUILD_EXTRA_WARN1 is defined, __maybe_unused is omitted from the 'inline' macro. This makes the code a bit uglier, so personally I do not want to carry this forever. If we can manage to fix most of the warnings, we can drop this entirely, then enable -Wunused-function all the time. If you contribute to code clean-up, please run "make CC=clang W=1" and check -Wunused-function warnings. You will find lots of unused functions. Some of them are false-positives because the call-sites are disabled by #ifdef. I do not like to abuse the inline keyword for suppressing unused-function warnings because it is intended to be a hint for the compiler optimization. I prefer #ifdef around the definition, or __maybe_unused if #ifdef would make the code too ugly. Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com> --- include/linux/compiler_types.h | 20 ++++++++++++++------ scripts/Makefile.extrawarn | 6 ++++++ 2 files changed, 20 insertions(+), 6 deletions(-)