+ revert-kbuild-avoid-static_assert-for-genksyms.patch added to -mm tree

[akpm@linux-foundation.org]

The patch titled
     Subject: Revert "kbuild: avoid static_assert for genksyms"
has been added to the -mm tree.  Its filename is
     revert-kbuild-avoid-static_assert-for-genksyms.patch

This patch should soon appear at
    https://ozlabs.org/~akpm/mmots/broken-out/revert-kbuild-avoid-static_assert-for-genksyms.patch
and later at
    https://ozlabs.org/~akpm/mmotm/broken-out/revert-kbuild-avoid-static_assert-for-genksyms.patch

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------------------------------------------------------
From: Masahiro Yamada <masahiroy@kernel.org>
Subject: Revert "kbuild: avoid static_assert for genksyms"

This reverts commit 14dc3983b5dff513a90bd5a8cc90acaf7867c3d0.

Macro Elver had sent a fix proper fix earlier, and also pointed out
corner cases:

"I guess what you propose is simpler, but might still have corner cases
where we still get warnings. In particular, if some file (for whatever
reason) does not include build_bug.h and uses a raw _Static_assert(),
then we still get warnings. E.g. I see 1 user of raw _Static_assert()
(drivers/gpu/drm/amd/amdgpu/amdgv_sriovmsg.h )."

I believe the raw use of _Static_assert() should be allowed, so this
should be fixed in genksyms.

Even after commit 14dc3983b5df ("kbuild: avoid static_assert for
genksyms"), I confirmed the following test code emits the warning.

  ---------------->8----------------
  #include <linux/export.h>

  _Static_assert((1 ?: 0), "");

  void foo(void) { }
  EXPORT_SYMBOL(foo);
  ---------------->8----------------

  WARNING: modpost: EXPORT symbol "foo" [vmlinux] version generation failed, symbol will not be versioned.

Now that commit 869b91992bce ("genksyms: Ignore module scoped
_Static_assert()") fixed this issue properly, the workaround should
be reverted.

Link: https://lkml.org/lkml/2020/12/10/845
Link: https://lkml.kernel.org/r/20201219183911.181442-1-masahiroy@kernel.org
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>
Cc: Marco Elver <elver@google.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 include/linux/build_bug.h |    5 -----
 1 file changed, 5 deletions(-)

--- a/include/linux/build_bug.h~revert-kbuild-avoid-static_assert-for-genksyms
+++ a/include/linux/build_bug.h
@@ -77,9 +77,4 @@
 #define static_assert(expr, ...) __static_assert(expr, ##__VA_ARGS__, #expr)
 #define __static_assert(expr, msg, ...) _Static_assert(expr, msg)
 
-#ifdef __GENKSYMS__
-/* genksyms gets confused by _Static_assert */
-#define _Static_assert(expr, ...)
-#endif
-
 #endif	/* _LINUX_BUILD_BUG_H */
_

Patches currently in -mm which might be from masahiroy@kernel.org are

revert-kbuild-avoid-static_assert-for-genksyms.patch