fortify: Ensure that __glibc_fortify condition is a constant [BZ #29141]

The fix c8ee1c85 introduced a -1 check for object size without also
checking that object size is a constant.  Because of this, the tree
optimizer passes in gcc fail to fold away one of the branches in
__glibc_fortify and trips on a spurious Wstringop-overflow.  The warning
itself is incorrect and the branch does go away eventually in DCE in the
rtl passes in gcc, but the constant check is a helpful hint to simplify
code early, so add it in.

Resolves: BZ #29141
Signed-off-by: Siddhesh Poyarekar <siddhesh@sourceware.org>
This commit is contained in:
Siddhesh Poyarekar 2022-05-13 10:01:47 +05:30
parent 0b6c675073
commit 61a8753010

View File

@ -164,7 +164,7 @@
/* Length is known to be safe at compile time if the __L * __S <= __OBJSZ
condition can be folded to a constant and if it is true, or unknown (-1) */
#define __glibc_safe_or_unknown_len(__l, __s, __osz) \
((__osz) == (__SIZE_TYPE__) -1 \
((__builtin_constant_p (__osz) && (__osz) == (__SIZE_TYPE__) -1) \
|| (__glibc_unsigned_or_positive (__l) \
&& __builtin_constant_p (__glibc_safe_len_cond ((__SIZE_TYPE__) (__l), \
(__s), (__osz))) \