https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78074
Bug ID: 78074
Summary: gcc-6.2.0 miscompiles calloc reimplementation
Product: gcc
Version: unknown
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: phelps at pobox dot com
Target Milestone: ---
For better or worse, tcsh provides its own malloc/calloc/realloc/free
functions. With gcc-6.2.0 (as supplied by Ubuntu-12.10, and also compiled from
sources), I'm seeing its realloc compiled into a infinite loop. Here is a
stripped down test case that loops indefinitely:
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
void *calloc(size_t nmemb, size_t size)
{
void *p = malloc(nmemb * size);
if (p != NULL)
memset(p, 0, nmemb * size);
return p;
}
int main(int argc, char *argv[])
{
char *value = calloc(64, 1);
printf("value=%p\n", value);
exit(0);
}
With -O2, it looks like gcc is interpreting the call to malloc as a call to
calloc instead:
(gdb) disassemble calloc
Dump of assembler code for function calloc:
0x0000000000000760 <+0>: imul %rsi,%rdi
0x0000000000000764 <+4>: mov $0x1,%esi
0x0000000000000769 <+9>: jmpq 0x760 <calloc>
End of assembler dump.
There's clearly something special about the names here: replacing calloc with
xcalloc produces code that runs fine.
