[Bug c/68334] New: combination of weak and noreturn attributes

["chantry.xavier at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=68334

            Bug ID: 68334
           Summary: combination of weak and noreturn attributes
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: chantry.xavier at gmail dot com
  Target Milestone: ---

It's probably more a nonsense than a bug, and all compilers behave the same way
(from gcc 4.4 to 5.2 and clang too).

If a function definition has both weak and noreturn, then it looks like the
noreturn optimization is applied anyway in the local compilation unit, even
though the function can be overriden by another one at link time.

main.c
---
#include <assert.h>
#include "test.h"

__attribute__((weak)) __attribute__((noreturn))
void test(void)
{
    assert (0);
}

int main(void)
{
    test();
    return 0;
}
---

test.c
---
#include <stdio.h>
#include "test.h"

void test(void)
{
    printf("toto\n");
}
---

test.h
---
void test(void);
---


$CC -Wall -Wextra -c test.c -o test.o
$CC -Wall -Wextra -c main.c -o main.o
$CC -Wall -Wextra main.o test.o -o test

Running ./test produces the following output which shows that the function was
overriden but the code is executed twice and then segfaults:
---
toto
toto
zsh: segmentation fault (core dumped)  ./test
---

I thought that noreturn optim shouldn't be applied in this case (it could maybe
still be done at linking time when using lto).
Otherwise I might have missed something in the doc which explains what's wrong.