Dear GCC Developers,

I think I've just discovered a bug/ undefined situation in the compiler.
When I try to call a weakly defined function, compiler successfully
generates the code of calling procedure. However, this calling procedure is
nothing but branching to address 0 which results in segmentation fault. I
am not sure if this is the case for the latest version of GCC but it is for
GCC 4.9.2 and many online compilers. I just thought that maybe including a
rule that generates compilation error when the user defines a weak function
and calls it without actually implementing it. You may find the results in
the attachments.

Kind regards,
I am looking forward to hearing from you about this.
Şahin Duran


Attachments:

Source Code:
#include <stdio.h>
#include <stdlib.h>
#include "header.h"

__attribute__((weak)) int add(int,int);

int main(int argc, char *argv[]) {
printf("%x",add);
add(31,31);
return 0;
}
terminal result : 0

Disassembly (on a 64bit AMD Machine):
0x0000000000401530 <+0>: push   rbp
   0x0000000000401531 <+1>: mov    rbp,rsp
   0x0000000000401534 <+4>: sub    rsp,0x20
   0x0000000000401538 <+8>: mov    DWORD PTR [rbp+0x10],ecx
   0x000000000040153b <+11>: mov    QWORD PTR [rbp+0x18],rdx
   0x000000000040153f <+15>: call   0x402100 <__main>
   0x0000000000401544 <+20>: mov    rdx,QWORD PTR [rip+0x2ed5]        #
0x404420 <.refptr.add>
   0x000000000040154b <+27>: lea    rcx,[rip+0x2aae]        # 0x404000
   0x0000000000401552 <+34>: call   0x402b18 <printf>
=> 0x0000000000401557 <+39>: mov    edx,0x1f
   0x000000000040155c <+44>: mov    ecx,0x1f
   0x0000000000401561 <+49>: call   0x0
   0x0000000000401566 <+54>: mov    eax,0x0
   0x000000000040156b <+59>: add    rsp,0x20
   0x000000000040156f <+63>: pop    rbp
   0x0000000000401570 <+64>: ret

Reply via email to