https://gcc.gnu.org/bugzilla/show_bug.cgi?id=94815
Bug ID: 94815
Summary: Abusive -Wrestrict warning with sprintf
Product: gcc
Version: 10.0
Status: UNCONFIRMED
Severity: normal
Priority: P3
Component: c
Assignee: unassigned at gcc dot gnu.org
Reporter: vincent.riviere at freesbee dot fr
Target Milestone: ---
Target: m68k-elf
Testcase:
$ cat foo.c && m68k-elf-gcc -c foo.c -Wall -O
char *strcpy(char *, const char *);
int sprintf(char *, const char *, ...);
char* myalloc(int n);
void f(void)
{
char* buf = myalloc(20);
char* str1 = buf;
char* str2 = buf + 10;
strcpy(str2, "123");
sprintf(str1, "ABC%s", str2);
}
foo.c: In function 'f':
foo.c:13:5: warning: 'sprintf' argument 3 may overlap destination object 'buf'
[-Wrestrict]
13 | sprintf(str1, "ABC%s", str2);
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
This warning is a unexpected because:
1) strcpy() and sprintf() are declared without __restrict, but __restrict rules
are still actually used.
2) In this simple example, it is obvious that the buffer will not overflow.
This is annoying, because it prevents creating several logical buffers from a
single allocation.
