diff mbox series

[2/2] kbuild: add -Wundef to KBUILD_CPPFLAGS for W=1 builds

Message ID	20221206040731.442499-2-masahiroy@kernel.org
State	New
Headers	Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20; From: Masahiro Yamada <masahiroy@kernel.org> To: linux-kbuild@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Masahiro Yamada <masahiroy@kernel.org>, Nathan Chancellor <nathan@kernel.org>, Nick Desaulniers <ndesaulniers@google.com>, Nicolas Schier <nicolas@fjasle.eu> Subject: [PATCH 2/2] kbuild: add -Wundef to KBUILD_CPPFLAGS for W=1 builds Date: Tue, 6 Dec 2022 13:07:31 +0900 Message-Id: <20221206040731.442499-2-masahiroy@kernel.org> In-Reply-To: <20221206040731.442499-1-masahiroy@kernel.org> References: <20221206040731.442499-1-masahiroy@kernel.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Precedence: bulk
Series	[1/2] kbuild: move -Werror from KBUILD_CFLAGS to KBUILD_CPPFLAGS \| [1/2] kbuild: move -Werror from KBUILD_CFLAGS to KBUILD_CPPFLAGS [2/2] kbuild: add -Wundef to KBUILD_CPPFLAGS for W=1 builds

Commit Message

Masahiro Yamada Dec. 6, 2022, 4:07 a.m. UTC

  The use of an undefined macro in an #if directive is warned, but only
in *.c files. No warning from other files such as *.S, *.lds.S.

Since -Wundef is a preprocessor-related warning, it should be added to
KBUILD_CPPFLAGS instead of KBUILD_CFLAGS.

My previous attempt [1] uncovered several warnings, and could not finish
fixing them all.

This commit adds -Wundef to KBUILD_CPPFLAGS for W=1 builds in order to
block new breakages. (The kbuild test robot tests with W=1)

We can fix the warnings one by one. After we fix all of them, we can
make this default in the top Makefile, and remove -Wundef from
KBUILD_CFLAGS.

[1]: https://lore.kernel.org/all/20221012180118.331005-2-masahiroy@kernel.org/

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

 scripts/Makefile.extrawarn | 1 +
 1 file changed, 1 insertion(+)

Comments

kernel test robot Dec. 6, 2022, 10:42 a.m. UTC | #1

Hi Masahiro,

I love your patch! Perhaps something to improve:

[auto build test WARNING on masahiroy-kbuild/for-next]
[also build test WARNING on masahiroy-kbuild/fixes linus/master v6.1-rc8 next-20221206]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Masahiro-Yamada/kbuild-move-Werror-from-KBUILD_CFLAGS-to-KBUILD_CPPFLAGS/20221206-120836
base:   https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git for-next
patch link:    https://lore.kernel.org/r/20221206040731.442499-2-masahiroy%40kernel.org
patch subject: [PATCH 2/2] kbuild: add -Wundef to KBUILD_CPPFLAGS for W=1 builds
config: i386-defconfig
compiler: gcc-11 (Debian 11.3.0-8) 11.3.0
reproduce (this is a W=1 build):
        # https://github.com/intel-lab-lkp/linux/commit/9c41976010ec03f9730df80eea55a21a79dda14a
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Masahiro-Yamada/kbuild-move-Werror-from-KBUILD_CFLAGS-to-KBUILD_CPPFLAGS/20221206-120836
        git checkout 9c41976010ec03f9730df80eea55a21a79dda14a
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        make W=1 O=build_dir ARCH=i386 SHELL=/bin/bash

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   In file included from arch/x86/kernel/head_32.S:29:
>> arch/x86/include/asm/pgtable_32.h:68:5: warning: "PTRS_PER_PMD" is not defined, evaluates to 0 [-Wundef]
      68 | #if PTRS_PER_PMD > 1
         |     ^~~~~~~~~~~~


vim +/PTRS_PER_PMD +68 arch/x86/include/asm/pgtable_32.h

^1da177e4c3f41 include/asm-i386/pgtable.h        Linus Torvalds  2005-04-16  58  
1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  59  /*
ea3186b9572a1b arch/x86/include/asm/pgtable_32.h Arvind Sankar   2020-10-29  60   * This is used to calculate the .brk reservation for initial pagetables.
ea3186b9572a1b arch/x86/include/asm/pgtable_32.h Arvind Sankar   2020-10-29  61   * Enough space is reserved to allocate pagetables sufficient to cover all
ea3186b9572a1b arch/x86/include/asm/pgtable_32.h Arvind Sankar   2020-10-29  62   * of LOWMEM_PAGES, which is an upper bound on the size of the direct map of
ea3186b9572a1b arch/x86/include/asm/pgtable_32.h Arvind Sankar   2020-10-29  63   * lowmem.
1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  64   *
ea3186b9572a1b arch/x86/include/asm/pgtable_32.h Arvind Sankar   2020-10-29  65   * With PAE paging (PTRS_PER_PMD > 1), we allocate PTRS_PER_PGD == 4 pages for
ea3186b9572a1b arch/x86/include/asm/pgtable_32.h Arvind Sankar   2020-10-29  66   * the PMD's in addition to the pages required for the last level pagetables.
1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  67   */
1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08 @68  #if PTRS_PER_PMD > 1
1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  69  #define PAGE_TABLE_SIZE(pages) (((pages) / PTRS_PER_PMD) + PTRS_PER_PGD)
1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  70  #else
1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  71  #define PAGE_TABLE_SIZE(pages) ((pages) / PTRS_PER_PGD)
1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  72  #endif
1e620f9b23e598 arch/x86/include/asm/pgtable_32.h Boris Ostrovsky 2016-12-08  73

kernel test robot Dec. 6, 2022, 10:42 a.m. UTC | #2

Hi Masahiro,

I love your patch! Perhaps something to improve:

[auto build test WARNING on masahiroy-kbuild/for-next]
[also build test WARNING on masahiroy-kbuild/fixes linus/master v6.1-rc8 next-20221206]
[If your patch is applied to the wrong git tree, kindly drop us a note.
And when submitting patch, we suggest to use '--base' as documented in
https://git-scm.com/docs/git-format-patch#_base_tree_information]

url:    https://github.com/intel-lab-lkp/linux/commits/Masahiro-Yamada/kbuild-move-Werror-from-KBUILD_CFLAGS-to-KBUILD_CPPFLAGS/20221206-120836
base:   https://git.kernel.org/pub/scm/linux/kernel/git/masahiroy/linux-kbuild.git for-next
patch link:    https://lore.kernel.org/r/20221206040731.442499-2-masahiroy%40kernel.org
patch subject: [PATCH 2/2] kbuild: add -Wundef to KBUILD_CPPFLAGS for W=1 builds
config: arm-randconfig-r006-20221205
compiler: arm-linux-gnueabi-gcc (GCC) 12.1.0
reproduce (this is a W=1 build):
        wget https://raw.githubusercontent.com/intel/lkp-tests/master/sbin/make.cross -O ~/bin/make.cross
        chmod +x ~/bin/make.cross
        # https://github.com/intel-lab-lkp/linux/commit/9c41976010ec03f9730df80eea55a21a79dda14a
        git remote add linux-review https://github.com/intel-lab-lkp/linux
        git fetch --no-tags linux-review Masahiro-Yamada/kbuild-move-Werror-from-KBUILD_CFLAGS-to-KBUILD_CPPFLAGS/20221206-120836
        git checkout 9c41976010ec03f9730df80eea55a21a79dda14a
        # save the config file
        mkdir build_dir && cp config build_dir/.config
        COMPILER_INSTALL_PATH=$HOME/0day COMPILER=gcc-12.1.0 make.cross W=1 O=build_dir ARCH=arm SHELL=/bin/bash arch/arm/

If you fix the issue, kindly add following tag where applicable
| Reported-by: kernel test robot <lkp@intel.com>

All warnings (new ones prefixed by >>):

   In file included from arch/arm/mm/cache-v7.S:17:
>> arch/arm/mm/proc-macros.S:109:5: warning: "L_PTE_SHARED" is not defined, evaluates to 0 [-Wundef]
     109 | #if L_PTE_SHARED != PTE_EXT_SHARED
         |     ^~~~~~~~~~~~
>> arch/arm/mm/proc-macros.S:109:21: warning: "PTE_EXT_SHARED" is not defined, evaluates to 0 [-Wundef]
     109 | #if L_PTE_SHARED != PTE_EXT_SHARED
         |                     ^~~~~~~~~~~~~~
>> arch/arm/mm/proc-macros.S:113:10: warning: "L_PTE_XN" is not defined, evaluates to 0 [-Wundef]
     113 |         (L_PTE_XN+L_PTE_USER+L_PTE_RDONLY+L_PTE_DIRTY+L_PTE_YOUNG+\
         |          ^~~~~~~~
>> arch/arm/mm/proc-macros.S:113:19: warning: "L_PTE_USER" is not defined, evaluates to 0 [-Wundef]
     113 |         (L_PTE_XN+L_PTE_USER+L_PTE_RDONLY+L_PTE_DIRTY+L_PTE_YOUNG+\
         |                   ^~~~~~~~~~
>> arch/arm/mm/proc-macros.S:113:30: warning: "L_PTE_RDONLY" is not defined, evaluates to 0 [-Wundef]
     113 |         (L_PTE_XN+L_PTE_USER+L_PTE_RDONLY+L_PTE_DIRTY+L_PTE_YOUNG+\
         |                              ^~~~~~~~~~~~
>> arch/arm/mm/proc-macros.S:113:43: warning: "L_PTE_DIRTY" is not defined, evaluates to 0 [-Wundef]
     113 |         (L_PTE_XN+L_PTE_USER+L_PTE_RDONLY+L_PTE_DIRTY+L_PTE_YOUNG+\
         |                                           ^~~~~~~~~~~
>> arch/arm/mm/proc-macros.S:113:55: warning: "L_PTE_YOUNG" is not defined, evaluates to 0 [-Wundef]
     113 |         (L_PTE_XN+L_PTE_USER+L_PTE_RDONLY+L_PTE_DIRTY+L_PTE_YOUNG+\
         |                                                       ^~~~~~~~~~~
>> arch/arm/mm/proc-macros.S:114:10: warning: "L_PTE_PRESENT" is not defined, evaluates to 0 [-Wundef]
     114 |          L_PTE_PRESENT) > L_PTE_SHARED
         |          ^~~~~~~~~~~~~
   arch/arm/mm/proc-macros.S:114:27: warning: "L_PTE_SHARED" is not defined, evaluates to 0 [-Wundef]
     114 |          L_PTE_PRESENT) > L_PTE_SHARED
         |                           ^~~~~~~~~~~~


vim +/L_PTE_SHARED +109 arch/arm/mm/proc-macros.S

9a1af5f2206bd30 Vladimir Murzin    2016-08-30   14  
^1da177e4c3f415 Linus Torvalds     2005-04-16   15  /*
^1da177e4c3f415 Linus Torvalds     2005-04-16   16   * vma_vm_mm - get mm pointer from vma pointer (vma->vm_mm)
^1da177e4c3f415 Linus Torvalds     2005-04-16   17   */
^1da177e4c3f415 Linus Torvalds     2005-04-16   18  	.macro	vma_vm_mm, rd, rn
^1da177e4c3f415 Linus Torvalds     2005-04-16   19  	ldr	\rd, [\rn, #VMA_VM_MM]
^1da177e4c3f415 Linus Torvalds     2005-04-16   20  	.endm
^1da177e4c3f415 Linus Torvalds     2005-04-16   21  
^1da177e4c3f415 Linus Torvalds     2005-04-16   22  /*
^1da177e4c3f415 Linus Torvalds     2005-04-16   23   * vma_vm_flags - get vma->vm_flags
^1da177e4c3f415 Linus Torvalds     2005-04-16   24   */
^1da177e4c3f415 Linus Torvalds     2005-04-16   25  	.macro	vma_vm_flags, rd, rn
^1da177e4c3f415 Linus Torvalds     2005-04-16   26  	ldr	\rd, [\rn, #VMA_VM_FLAGS]
^1da177e4c3f415 Linus Torvalds     2005-04-16   27  	.endm
^1da177e4c3f415 Linus Torvalds     2005-04-16   28  
^1da177e4c3f415 Linus Torvalds     2005-04-16   29  /*
^1da177e4c3f415 Linus Torvalds     2005-04-16   30   * act_mm - get current->active_mm
^1da177e4c3f415 Linus Torvalds     2005-04-16   31   */
^1da177e4c3f415 Linus Torvalds     2005-04-16   32  	.macro	act_mm, rd
50596b7559bf226 Ard Biesheuvel     2021-09-18   33  	get_current \rd
ffa47aa678cfaa9 Arnd Bergmann      2017-06-30   34  	.if (TSK_ACTIVE_MM > IMM12_MASK)
ffa47aa678cfaa9 Arnd Bergmann      2017-06-30   35  	add	\rd, \rd, #TSK_ACTIVE_MM & ~IMM12_MASK
ffa47aa678cfaa9 Arnd Bergmann      2017-06-30   36  	.endif
ffa47aa678cfaa9 Arnd Bergmann      2017-06-30   37  	ldr	\rd, [\rd, #TSK_ACTIVE_MM & IMM12_MASK]
^1da177e4c3f415 Linus Torvalds     2005-04-16   38  	.endm
^1da177e4c3f415 Linus Torvalds     2005-04-16   39  
^1da177e4c3f415 Linus Torvalds     2005-04-16   40  /*
^1da177e4c3f415 Linus Torvalds     2005-04-16   41   * mmid - get context id from mm pointer (mm->context.id)
9520a5bece13b73 Ben Dooks          2013-02-11   42   * note, this field is 64bit, so in big-endian the two words are swapped too.
^1da177e4c3f415 Linus Torvalds     2005-04-16   43   */
^1da177e4c3f415 Linus Torvalds     2005-04-16   44  	.macro	mmid, rd, rn
9520a5bece13b73 Ben Dooks          2013-02-11   45  #ifdef __ARMEB__
9520a5bece13b73 Ben Dooks          2013-02-11   46  	ldr	\rd, [\rn, #MM_CONTEXT_ID + 4 ]
9520a5bece13b73 Ben Dooks          2013-02-11   47  #else
^1da177e4c3f415 Linus Torvalds     2005-04-16   48  	ldr	\rd, [\rn, #MM_CONTEXT_ID]
9520a5bece13b73 Ben Dooks          2013-02-11   49  #endif
^1da177e4c3f415 Linus Torvalds     2005-04-16   50  	.endm
^1da177e4c3f415 Linus Torvalds     2005-04-16   51  
^1da177e4c3f415 Linus Torvalds     2005-04-16   52  /*
^1da177e4c3f415 Linus Torvalds     2005-04-16   53   * mask_asid - mask the ASID from the context ID
^1da177e4c3f415 Linus Torvalds     2005-04-16   54   */
^1da177e4c3f415 Linus Torvalds     2005-04-16   55  	.macro	asid, rd, rn
^1da177e4c3f415 Linus Torvalds     2005-04-16   56  	and	\rd, \rn, #255
^1da177e4c3f415 Linus Torvalds     2005-04-16   57  	.endm
22b1908610dd7ff Russell King       2006-06-29   58  
22b1908610dd7ff Russell King       2006-06-29   59  	.macro	crval, clear, mmuset, ucset
22b1908610dd7ff Russell King       2006-06-29   60  #ifdef CONFIG_MMU
22b1908610dd7ff Russell King       2006-06-29   61  	.word	\clear
22b1908610dd7ff Russell King       2006-06-29   62  	.word	\mmuset
22b1908610dd7ff Russell King       2006-06-29   63  #else
22b1908610dd7ff Russell King       2006-06-29   64  	.word	\clear
22b1908610dd7ff Russell King       2006-06-29   65  	.word	\ucset
22b1908610dd7ff Russell King       2006-06-29   66  #endif
22b1908610dd7ff Russell King       2006-06-29   67  	.endm
bbe888864ec3243 Catalin Marinas    2007-05-08   68  
bbe888864ec3243 Catalin Marinas    2007-05-08   69  /*
f91e2c3bd427239 Catalin Marinas    2010-12-07   70   * dcache_line_size - get the minimum D-cache line size from the CTR register
f91e2c3bd427239 Catalin Marinas    2010-12-07   71   * on ARMv7.
bbe888864ec3243 Catalin Marinas    2007-05-08   72   */
bbe888864ec3243 Catalin Marinas    2007-05-08   73  	.macro	dcache_line_size, reg, tmp
9a1af5f2206bd30 Vladimir Murzin    2016-08-30   74  #ifdef CONFIG_CPU_V7M
9a1af5f2206bd30 Vladimir Murzin    2016-08-30   75  	movw	\tmp, #:lower16:BASEADDR_V7M_SCB + V7M_SCB_CTR
9a1af5f2206bd30 Vladimir Murzin    2016-08-30   76  	movt	\tmp, #:upper16:BASEADDR_V7M_SCB + V7M_SCB_CTR
9a1af5f2206bd30 Vladimir Murzin    2016-08-30   77  	ldr     \tmp, [\tmp]
9a1af5f2206bd30 Vladimir Murzin    2016-08-30   78  #else
f91e2c3bd427239 Catalin Marinas    2010-12-07   79  	mrc	p15, 0, \tmp, c0, c0, 1		@ read ctr
9a1af5f2206bd30 Vladimir Murzin    2016-08-30   80  #endif
f91e2c3bd427239 Catalin Marinas    2010-12-07   81  	lsr	\tmp, \tmp, #16
f91e2c3bd427239 Catalin Marinas    2010-12-07   82  	and	\tmp, \tmp, #0xf		@ cache line size encoding
f91e2c3bd427239 Catalin Marinas    2010-12-07   83  	mov	\reg, #4			@ bytes per word
bbe888864ec3243 Catalin Marinas    2007-05-08   84  	mov	\reg, \reg, lsl \tmp		@ actual cache line size
bbe888864ec3243 Catalin Marinas    2007-05-08   85  	.endm
da0916539d20f25 Russell King       2008-09-06   86  
da30e0ac0f9a521 Catalin Marinas    2010-12-07   87  /*
da30e0ac0f9a521 Catalin Marinas    2010-12-07   88   * icache_line_size - get the minimum I-cache line size from the CTR register
da30e0ac0f9a521 Catalin Marinas    2010-12-07   89   * on ARMv7.
da30e0ac0f9a521 Catalin Marinas    2010-12-07   90   */
da30e0ac0f9a521 Catalin Marinas    2010-12-07   91  	.macro	icache_line_size, reg, tmp
9a1af5f2206bd30 Vladimir Murzin    2016-08-30   92  #ifdef CONFIG_CPU_V7M
9a1af5f2206bd30 Vladimir Murzin    2016-08-30   93  	movw	\tmp, #:lower16:BASEADDR_V7M_SCB + V7M_SCB_CTR
9a1af5f2206bd30 Vladimir Murzin    2016-08-30   94  	movt	\tmp, #:upper16:BASEADDR_V7M_SCB + V7M_SCB_CTR
9a1af5f2206bd30 Vladimir Murzin    2016-08-30   95  	ldr     \tmp, [\tmp]
9a1af5f2206bd30 Vladimir Murzin    2016-08-30   96  #else
da30e0ac0f9a521 Catalin Marinas    2010-12-07   97  	mrc	p15, 0, \tmp, c0, c0, 1		@ read ctr
9a1af5f2206bd30 Vladimir Murzin    2016-08-30   98  #endif
da30e0ac0f9a521 Catalin Marinas    2010-12-07   99  	and	\tmp, \tmp, #0xf		@ cache line size encoding
da30e0ac0f9a521 Catalin Marinas    2010-12-07  100  	mov	\reg, #4			@ bytes per word
da30e0ac0f9a521 Catalin Marinas    2010-12-07  101  	mov	\reg, \reg, lsl \tmp		@ actual cache line size
da30e0ac0f9a521 Catalin Marinas    2010-12-07  102  	.endm
da0916539d20f25 Russell King       2008-09-06  103  
da0916539d20f25 Russell King       2008-09-06  104  /*
da0916539d20f25 Russell King       2008-09-06  105   * Sanity check the PTE configuration for the code below - which makes
25985edcedea639 Lucas De Marchi    2011-03-30  106   * certain assumptions about how these bits are laid out.
da0916539d20f25 Russell King       2008-09-06  107   */
8b79d5f217d7fc7 Catalin Marinas    2009-07-24  108  #ifdef CONFIG_MMU
da0916539d20f25 Russell King       2008-09-06 @109  #if L_PTE_SHARED != PTE_EXT_SHARED
da0916539d20f25 Russell King       2008-09-06  110  #error PTE shared bit mismatch
da0916539d20f25 Russell King       2008-09-06  111  #endif
1b6ba46b7efa310 Catalin Marinas    2011-11-22  112  #if !defined (CONFIG_ARM_LPAE) && \
1b6ba46b7efa310 Catalin Marinas    2011-11-22 @113  	(L_PTE_XN+L_PTE_USER+L_PTE_RDONLY+L_PTE_DIRTY+L_PTE_YOUNG+\
b007ea798f5c568 Kirill A. Shutemov 2015-02-10 @114  	 L_PTE_PRESENT) > L_PTE_SHARED
da0916539d20f25 Russell King       2008-09-06  115  #error Invalid Linux PTE bit settings
da0916539d20f25 Russell King       2008-09-06  116  #endif
8b79d5f217d7fc7 Catalin Marinas    2009-07-24  117  #endif	/* CONFIG_MMU */
da0916539d20f25 Russell King       2008-09-06  118

Nathan Chancellor Dec. 9, 2022, 5:49 p.m. UTC | #3

On Tue, Dec 06, 2022 at 01:07:31PM +0900, Masahiro Yamada wrote:
> The use of an undefined macro in an #if directive is warned, but only
> in *.c files. No warning from other files such as *.S, *.lds.S.
> 
> Since -Wundef is a preprocessor-related warning, it should be added to
> KBUILD_CPPFLAGS instead of KBUILD_CFLAGS.
> 
> My previous attempt [1] uncovered several warnings, and could not finish
> fixing them all.
> 
> This commit adds -Wundef to KBUILD_CPPFLAGS for W=1 builds in order to
> block new breakages. (The kbuild test robot tests with W=1)
> 
> We can fix the warnings one by one. After we fix all of them, we can
> make this default in the top Makefile, and remove -Wundef from
> KBUILD_CFLAGS.
> 
> [1]: https://lore.kernel.org/all/20221012180118.331005-2-masahiroy@kernel.org/
> 
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Reviewed-by: Nathan Chancellor <nathan@kernel.org>

Looks like the robot already found a few so this clearly works as
intended.

> ---
> 
>  scripts/Makefile.extrawarn | 1 +
>  1 file changed, 1 insertion(+)
> 
> diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
> index 6bbba36c5969..40cd13eca82e 100644
> --- a/scripts/Makefile.extrawarn
> +++ b/scripts/Makefile.extrawarn
> @@ -38,6 +38,7 @@ KBUILD_CFLAGS += -Wno-sign-compare
>  KBUILD_CFLAGS += -Wno-type-limits
>  KBUILD_CFLAGS += -Wno-shift-negative-value
>  
> +KBUILD_CPPFLAGS += -Wundef
>  KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
>  
>  else
> -- 
> 2.34.1
> 
>

Nick Desaulniers Dec. 9, 2022, 6:29 p.m. UTC | #4

On Mon, Dec 5, 2022 at 8:07 PM Masahiro Yamada <masahiroy@kernel.org> wrote:
>
> The use of an undefined macro in an #if directive is warned, but only
> in *.c files. No warning from other files such as *.S, *.lds.S.
>
> Since -Wundef is a preprocessor-related warning, it should be added to
> KBUILD_CPPFLAGS instead of KBUILD_CFLAGS.
>
> My previous attempt [1] uncovered several warnings, and could not finish
> fixing them all.
>
> This commit adds -Wundef to KBUILD_CPPFLAGS for W=1 builds in order to
> block new breakages. (The kbuild test robot tests with W=1)
>
> We can fix the warnings one by one. After we fix all of them, we can
> make this default in the top Makefile, and remove -Wundef from
> KBUILD_CFLAGS.

I like that approach.
Reviewed-by: Nick Desaulniers <ndesaulniers@google.com>

>
> [1]: https://lore.kernel.org/all/20221012180118.331005-2-masahiroy@kernel.org/
>
> Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
> ---
>
>  scripts/Makefile.extrawarn | 1 +
>  1 file changed, 1 insertion(+)
>
> diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
> index 6bbba36c5969..40cd13eca82e 100644
> --- a/scripts/Makefile.extrawarn
> +++ b/scripts/Makefile.extrawarn
> @@ -38,6 +38,7 @@ KBUILD_CFLAGS += -Wno-sign-compare
>  KBUILD_CFLAGS += -Wno-type-limits
>  KBUILD_CFLAGS += -Wno-shift-negative-value
>
> +KBUILD_CPPFLAGS += -Wundef
>  KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
>
>  else
> --
> 2.34.1
>

diff mbox series

Patch

diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn
index 6bbba36c5969..40cd13eca82e 100644
--- a/scripts/Makefile.extrawarn
+++ b/scripts/Makefile.extrawarn
@@ -38,6 +38,7 @@  KBUILD_CFLAGS += -Wno-sign-compare
 KBUILD_CFLAGS += -Wno-type-limits
 KBUILD_CFLAGS += -Wno-shift-negative-value
 
+KBUILD_CPPFLAGS += -Wundef
 KBUILD_CPPFLAGS += -DKBUILD_EXTRA_WARN1
 
 else