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* [Bug tree-optimization/92486] Wrong optimization: padding in structs is not copied even with memcpy
[not found] <bug-92486-4@http.gcc.gnu.org/bugzilla/>
@ 2020-03-20 11:23 ` ch3root at openwall dot com
0 siblings, 0 replies; only message in thread
From: ch3root at openwall dot com @ 2020-03-20 11:23 UTC (permalink / raw)
To: gcc-bugs
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=92486
--- Comment #18 from Alexander Cherepanov <ch3root at openwall dot com> ---
Adding a `memset` makes trunk fail too:
----------------------------------------------------------------------
#include <string.h>
#include <stdio.h>
struct s {
char c;
int i;
};
__attribute__((noinline,noclone))
void f(struct s *p, struct s *q)
{
struct s w;
memset(&w, 0, sizeof(struct s));
w = *q;
memcpy(&w, q, sizeof(struct s));
*p = w;
memcpy(p, &w, sizeof(struct s));
}
int main()
{
struct s x;
memset(&x, 1, sizeof(struct s));
struct s y;
memset(&y, 2, sizeof(struct s));
f(&y, &x);
for (unsigned char *p = (unsigned char *)&y; p < (unsigned char *)&y +
sizeof(struct s); p++)
printf("%d", *p);
printf("\n");
}
----------------------------------------------------------------------
$ gcc -std=c11 -pedantic -Wall -Wextra test.c && ./a.out
11111111
$ gcc -std=c11 -pedantic -Wall -Wextra -O3 test.c && ./a.out
12221111
----------------------------------------------------------------------
gcc x86-64 version: gcc (GCC) 10.0.1 20200320 (experimental)
----------------------------------------------------------------------
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[not found] <bug-92486-4@http.gcc.gnu.org/bugzilla/>
2020-03-20 11:23 ` [Bug tree-optimization/92486] Wrong optimization: padding in structs is not copied even with memcpy ch3root at openwall dot com
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