# git rev-parse -q --verify 3c8ba0d61d04ced9f8d9ff93977995a9e4e96e91^{commit}
3c8ba0d61d04ced9f8d9ff93977995a9e4e96e91
already have revision, skipping fetch
# git checkout -q -f -B kisskb 3c8ba0d61d04ced9f8d9ff93977995a9e4e96e91
# git clean -qxdf
# < git log -1
# commit 3c8ba0d61d04ced9f8d9ff93977995a9e4e96e91
# Author: Kees Cook <keescook@chromium.org>
# Date:   Fri Mar 30 18:52:36 2018 -0700
# 
#     kernel.h: Retain constant expression output for max()/min()
#     
#     In the effort to remove all VLAs from the kernel[1], it is desirable to
#     build with -Wvla.  However, this warning is overly pessimistic, in that
#     it is only happy with stack array sizes that are declared as constant
#     expressions, and not constant values.  One case of this is the
#     evaluation of the max() macro which, due to its construction, ends up
#     converting constant expression arguments into a constant value result.
#     
#     All attempts to rewrite this macro with __builtin_constant_p() failed
#     with older compilers (e.g.  gcc 4.4)[2].  However, Martin Uecker,
#     constructed[3] a mind-shattering solution that works everywhere.
#     Cthulhu fhtagn!
#     
#     This patch updates the min()/max() macros to evaluate to a constant
#     expression when called on constant expression arguments.  This removes
#     several false-positive stack VLA warnings from an x86 allmodconfig build
#     when -Wvla is added:
#     
#       $ diff -u before.txt after.txt | grep ^-
#       -drivers/input/touchscreen/cyttsp4_core.c:871:2: warning: ISO C90 forbids variable length array ‘ids’ [-Wvla]
#       -fs/btrfs/tree-checker.c:344:4: warning: ISO C90 forbids variable length array ‘namebuf’ [-Wvla]
#       -lib/vsprintf.c:747:2: warning: ISO C90 forbids variable length array ‘sym’ [-Wvla]
#       -net/ipv4/proc.c:403:2: warning: ISO C90 forbids variable length array ‘buff’ [-Wvla]
#       -net/ipv6/proc.c:198:2: warning: ISO C90 forbids variable length array ‘buff’ [-Wvla]
#       -net/ipv6/proc.c:218:2: warning: ISO C90 forbids variable length array ‘buff64’ [-Wvla]
#     
#     This also updates two cases where different enums were being compared
#     and explicitly casts them to int (which matches the old side-effect of
#     the single-evaluation code): one in tpm/tpm_tis_core.h, and one in
#     drm/drm_color_mgmt.c.
#     
#      [1] https://lkml.org/lkml/2018/3/7/621
#      [2] https://lkml.org/lkml/2018/3/10/170
#      [3] https://lkml.org/lkml/2018/3/20/845
#     
#     Co-Developed-by: Linus Torvalds <torvalds@linux-foundation.org>
#     Co-Developed-by: Martin Uecker <Martin.Uecker@med.uni-goettingen.de>
#     Signed-off-by: Kees Cook <keescook@chromium.org>
#     Acked-by: Ingo Molnar <mingo@kernel.org>
#     Acked-by: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com>
#     Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
# < /opt/cross/kisskb/gcc-4.6.3-nolibc/i386-linux/bin/i386-linux-gcc --version
# < git log --format=%s --max-count=1 3c8ba0d61d04ced9f8d9ff93977995a9e4e96e91
# < make -s -j 48 ARCH=i386 O=/kisskb/build/linus_i386-allnoconfig_i386 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/i386-linux/bin/i386-linux-  allnoconfig
# make -s -j 48 ARCH=i386 O=/kisskb/build/linus_i386-allnoconfig_i386 CROSS_COMPILE=/opt/cross/kisskb/gcc-4.6.3-nolibc/i386-linux/bin/i386-linux-  
CONFIG_CC_STACKPROTECTOR_AUTO: -fstack-protector available but compiler is broken: disabling
/kisskb/src/arch/x86/kernel/e820.c: In function 'e820__setup_pci_gap':
/kisskb/src/arch/x86/kernel/e820.c:650:16: warning: 'gapstart' may be used uninitialized in this function [-Wuninitialized]
/kisskb/src/kernel/printk/printk.c: In function 'devkmsg_sysctl_set_loglvl':
/kisskb/src/kernel/printk/printk.c:183:16: warning: 'old' may be used uninitialized in this function [-Wuninitialized]
Completed OK
# rm -rf /kisskb/build/linus_i386-allnoconfig_i386
# Build took: 0:00:13.890426