Kbuild: use -std=gnu11 for KBUILD_USERCFLAGS

As we change the C language standard for the kernel from gnu89 to
gnu11, it makes sense to also update the version for user space
compilation.

Some users have older native compilers than what they use for
kernel builds, so I considered using gnu99 as the default version
for wider compatibility with gcc-4.6 and earlier.

However, testing with older compilers showed that we already require
HOSTCC version 5.1 as well because a lot of host tools include
linux/compiler.h that uses __has_attribute():

  CC      tools/objtool/exec-cmd.o
In file included from tools/include/linux/compiler_types.h:36:0,
                 from tools/include/linux/compiler.h:5,
                 from exec-cmd.c:2:
tools/include/linux/compiler-gcc.h:19:5: error: "__has_attribute" is not defined [-Werror=undef]

Signed-off-by: Arnd Bergmann <[email protected]>
Reviewed-by: Nathan Chancellor <[email protected]>
Reviewed-by: Nick Desaulniers <[email protected]>
Tested-by: Sedat Dilek <[email protected]>
Signed-off-by: Masahiro Yamada <[email protected]>

1 files changed, 1 insertions, 1 deletions

diff --git a/Makefile b/Makefile
index 19b4f75d42c2..8a18fa1e19a7 100644
--- a/Makefile
+++ b/Makefile
@@ -432,7 +432,7 @@ HOSTCXX	= g++
 endif
 
 export KBUILD_USERCFLAGS := -Wall -Wmissing-prototypes -Wstrict-prototypes \
-			      -O2 -fomit-frame-pointer -std=gnu89 \
+			      -O2 -fomit-frame-pointer -std=gnu11 \
 			      -Wdeclaration-after-statement
 export KBUILD_USERLDFLAGS :=