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compiletime_assert() uses __LINE__ to create a unique function name. This
means that if you have more than one BUILD_BUG_ON() in the same source
line (which can happen if they appear e.g. in a macro), then the error
message from the compiler might output the wrong condition.
For this source file:
#include <linux/build_bug.h>
#define macro() \
BUILD_BUG_ON(1); \
BUILD_BUG_ON(0);
void foo()
{
macro();
}
gcc would output:
./include/linux/compiler.h:350:38: error: call to `__compiletime_assert_9' declared with attribute error: BUILD_BUG_ON failed: 0
_compiletime_assert(condition, msg, __compiletime_assert_, __LINE__)
However, it was not the BUILD_BUG_ON(0) that failed, so it should say 1
instead of 0. With this patch, we use __COUNTER__ instead of __LINE__, so
each BUILD_BUG_ON() gets a different function name and the correct
condition is printed:
./include/linux/compiler.h:350:38: error: call to `__compiletime_assert_0' declared with attribute error: BUILD_BUG_ON failed: 1
_compiletime_assert(condition, msg, __compiletime_assert_, __COUNTER__)
Signed-off-by: Vegard Nossum <vegard.nossum@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Reviewed-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Daniel Santos <daniel.santos@pobox.com>
Cc: Rasmus Villemoes <linux@rasmusvillemoes.dk>
Cc: Ian Abbott <abbotti@mev.co.uk>
Cc: Joe Perches <joe@perches.com>
Link: http://lkml.kernel.org/r/20200331112637.25047-1-vegard.nossum@oracle.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.