https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83456
Bug ID: 83456
Summary: -Wrestrict false positive on a non-overlapping memcpy
in an inline function
Product: gcc
Version: 8.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: tree-optimization
Assignee: unassigned at gcc dot gnu.org
Reporter: msebor at gcc dot gnu.org
Target Milestone: ---
As reported in bug 78918, comment #7, the enhanced -Wrestrict warning issues a
false positive on the following code. The false positive is caused by issuing
the warning during folding, after bar() has been inlined but before the call to
memcpy has been eliminated. The reason for issuing the warning in this case
(i.e., equal operands) is to help detect bugs in code built without
optimization when an unguarded overlapping call to the library function would
be made, but it may not be worth the bug reports for the safe cases like this
one.
$ cat z.c && gcc -O2 -S -Wall z.c
extern void* memcpy (void*, const void*, __SIZE_TYPE__);
inline void bar (void *d, void *s, unsigned N)
{
if (s != d)
memcpy (d, s, N);
}
void foo (void* src)
{
bar (src, src, 1);
}
z.c: In function ‘foo’:
z.c:6:5: warning: ‘memcpy’ source argument is the same as destination
[-Wrestrict]
memcpy (d, s, N);
^~~~~~~~~~~~~~~~
