https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86196
Bug ID: 86196
Summary: Bogus -Wrestrict on memcpy
Product: gcc
Version: 9.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: sbergman at redhat dot com
Target Milestone: ---
With recent trunk (on Linux x86_64), and doesn't seem to be covered by existing
bugs referenced from meta bug 84774:
> $ gcc --version
> gcc (GCC) 9.0.0 20180618 (experimental)
> Copyright (C) 2018 Free Software Foundation, Inc.
> This is free software; see the source for copying conditions. There is NO
> warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
> $ cat test.c
> #include <string.h>
> struct S {
> int n;
> void * p;
> };
> void f(struct S * a, size_t n) {
> size_t i = 0, j = 0;
> for (; i != n; ++i) {
> if (a[i].n == 0) {
> if (i != j) {
> memcpy(&a[j], &a[i], sizeof (struct S));
> }
> ++j;
> }
> }
> }
> $ gcc -Wall -c test.c
> test.c: In function ‘f’:
> test.c:11:17: warning: ‘memcpy’ accessing 16 bytes at offsets [0, 8] and [0,
> 8] overlaps between 8 and 16 bytes at offset [0, 8] [-Wrestrict]
> memcpy(&a[j], &a[i], sizeof (struct S));
> ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Also, I do not understand what that "offset [0, 8]" notation is supposed to
mean.
