# git rev-parse -q --verify ee07f8442ecdc5450f2a10dd86443b822e4d96ec^{commit}
ee07f8442ecdc5450f2a10dd86443b822e4d96ec
already have revision, skipping fetch
# git checkout -q -f -B kisskb ee07f8442ecdc5450f2a10dd86443b822e4d96ec
# git clean -qxdf
# < git log -1
# commit ee07f8442ecdc5450f2a10dd86443b822e4d96ec
# Author: Gustavo A. R. Silva <gustavoars@kernel.org>
# Date:   Thu May 28 09:35:11 2020 -0500
# 
#     w1: Replace zero-length array with flexible-array
#     
#     The current codebase makes use of the zero-length array language
#     extension to the C90 standard, but the preferred mechanism to declare
#     variable-length types such as these ones is a flexible array member[1][2],
#     introduced in C99:
#     
#     struct foo {
#             int stuff;
#             struct boo array[];
#     };
#     
#     By making use of the mechanism above, we will get a compiler warning
#     in case the flexible array does not occur last in the structure, which
#     will help us prevent some kind of undefined behavior bugs from being
#     inadvertently introduced[3] to the codebase from now on.
#     
#     Also, notice that, dynamic memory allocations won't be affected by
#     this change:
#     
#     "Flexible array members have incomplete type, and so the sizeof operator
#     may not be applied. As a quirk of the original implementation of
#     zero-length arrays, sizeof evaluates to zero."[1]
#     
#     sizeof(flexible-array-member) triggers a warning because flexible array
#     members have incomplete type[1]. There are some instances of code in
#     which the sizeof operator is being incorrectly/erroneously applied to
#     zero-length arrays and the result is zero. Such instances may be hiding
#     some bugs. So, this work (flexible-array member conversions) will also
#     help to get completely rid of those sorts of issues.
#     
#     Notice that, currently, more than 250 of these patches have already
#     been merged into mainline during the last merge window, including
#     5.7-rc2. So, in order to make better use of everyone's time, I'm
#     planning to add this treewide patch to my -next tree and then send a
#     pull request to Linus for 5.7-rc3 or -rc4, after getting some acks
#     and/or reviews.
#     
#     This treewide patch has been successfully built (on top of v5.7-rc1) for
#     multiple architectures (arm, arm64, sparc, powerpc, ia64, s390, i386,
#     nios2, c6x, xtensa, openrisc, mips, parisc, x86_64, riscv, sh, sparc64)
#     and 82 different configurations with the help of the 0-day CI guys[5].
#     
#     This issue was found with the help of Coccinelle.
#     
#     [1] https://gcc.gnu.org/onlinedocs/gcc/Zero-Length.html
#     [2] https://github.com/KSPP/linux/issues/21
#     [3] commit 76497732932f ("cxgb3/l2t: Fix undefined behaviour")
#     [4] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/log/?qt=grep&q=replace+zero-leng
#     
#     Signed-off-by: Gustavo A. R. Silva <gustavoars@kernel.org>
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/ia64-linux/bin/ia64-linux-gcc --version
# < /opt/cross/kisskb/korg/gcc-4.9.4-nolibc/ia64-linux/bin/ia64-linux-ld --version
# < git log --format=%s --max-count=1 ee07f8442ecdc5450f2a10dd86443b822e4d96ec
# < make -s -j 48 ARCH=ia64 O=/kisskb/build/gustavoars_ia64-defconfig_ia64-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/ia64-linux/bin/ia64-linux-  defconfig
# < make -s -j 48 ARCH=ia64 O=/kisskb/build/gustavoars_ia64-defconfig_ia64-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/ia64-linux/bin/ia64-linux-  help
# make -s -j 48 ARCH=ia64 O=/kisskb/build/gustavoars_ia64-defconfig_ia64-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/ia64-linux/bin/ia64-linux-  olddefconfig
# make -s -j 48 ARCH=ia64 O=/kisskb/build/gustavoars_ia64-defconfig_ia64-gcc4.9 CROSS_COMPILE=/opt/cross/kisskb/korg/gcc-4.9.4-nolibc/ia64-linux/bin/ia64-linux-  
<stdin>:1511:2: warning: #warning syscall clone3 not implemented [-Wcpp]
In file included from /kisskb/src/arch/ia64/include/uapi/asm/intrinsics.h:22:0,
                 from /kisskb/src/arch/ia64/include/asm/intrinsics.h:11,
                 from /kisskb/src/arch/ia64/include/asm/bitops.h:19,
                 from /kisskb/src/include/linux/bitops.h:29,
                 from /kisskb/src/include/linux/kernel.h:12,
                 from /kisskb/src/include/linux/list.h:9,
                 from /kisskb/src/include/linux/preempt.h:11,
                 from /kisskb/src/include/linux/spinlock.h:51,
                 from /kisskb/src/include/linux/seqlock.h:36,
                 from /kisskb/src/include/linux/time.h:6,
                 from /kisskb/src/fs/nfs/read.c:11:
/kisskb/src/fs/nfs/read.c: In function 'nfs_read_completion':
/kisskb/src/arch/ia64/include/uapi/asm/cmpxchg.h:57:2: warning: value computed is not used [-Wunused-value]
 ((__typeof__(*(ptr))) __xchg((unsigned long) (x), (ptr), sizeof(*(ptr))))
  ^
/kisskb/src/fs/nfs/read.c:196:5: note: in expansion of macro 'xchg'
     xchg(&nfs_req_openctx(req)->error, error);
     ^
/kisskb/src/fs/nfs/read.c: In function 'nfs_readpage':
/kisskb/src/arch/ia64/include/uapi/asm/cmpxchg.h:57:2: warning: value computed is not used [-Wunused-value]
 ((__typeof__(*(ptr))) __xchg((unsigned long) (x), (ptr), sizeof(*(ptr))))
  ^
/kisskb/src/fs/nfs/read.c:353:2: note: in expansion of macro 'xchg'
  xchg(&ctx->error, 0);
  ^
/kisskb/src/drivers/gpu/drm/drm_dp_mst_topology.c: In function 'drm_dp_mst_dsc_aux_for_port':
/kisskb/src/drivers/gpu/drm/drm_dp_mst_topology.c:5502:9: warning: missing braces around initializer [-Wmissing-braces]
  struct drm_dp_desc desc = { 0 };
         ^
/kisskb/src/drivers/gpu/drm/drm_dp_mst_topology.c:5502:9: warning: (near initialization for 'desc.ident') [-Wmissing-braces]
No errors detected in 22168 functions.
Completed OK
# rm -rf /kisskb/build/gustavoars_ia64-defconfig_ia64-gcc4.9
# Build took: 0:02:24.812897