| Message ID | 20220513043242.805338-1-siddhesh@sourceware.org |
|---|---|
| State | New |
| Headers | show |
| Series | fortify: Ensure that __glibc_fortify condition is a constant [BZ #29141] | expand |
* Siddhesh Poyarekar: > 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> > --- > misc/sys/cdefs.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h > index f1faf8292c..1c2b044a0d 100644 > --- a/misc/sys/cdefs.h > +++ b/misc/sys/cdefs.h > @@ -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))) \ I *think* this is okay based on localized review. Thanks, Florian
diff --git a/misc/sys/cdefs.h b/misc/sys/cdefs.h index f1faf8292c..1c2b044a0d 100644 --- a/misc/sys/cdefs.h +++ b/misc/sys/cdefs.h @@ -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))) \
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> --- misc/sys/cdefs.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-)