Re: Define __start/__stop symbols when there is only a dynamic def

["H.J. Lu" <hjl dot tools at gmail dot com>]

On Mon, Jan 29, 2018 at 8:50 AM, Michael Matz <matz@suse.de> wrote:
> Hi,
>
> On Mon, 29 Jan 2018, H.J. Lu wrote:
>
>> We need a run-time testcase.  Can you provide a run-time testcase?
>
> Replace app.c from last mail with this, add -ldl as appropriate.  Only
> works on systems that have RTLD_DEFAULT (RTLD_SELF could also be used, but
> those are are subset of the former).
>
> % cat app.c
> #define _GNU_SOURCE
> #include <stdlib.h>
> #include <stdio.h>
> #include <dlfcn.h>
>
> extern int __start___verbose[];
> extern int __stop___verbose[];
> int bar (void)
> {
>   static int my_var __attribute__((section("__verbose"))) = 6;
>   int *ptr;
>   ptr = (int*) dlsym(RTLD_DEFAULT, "__start___verbose");
>   if (!ptr || *ptr != 6)
>     return -1;
>   return 0;
> }
>
> int main()
> {
>   if (bar () != 0)
>     {
>       printf("main: wrong __start___verbose\n");
>       exit(2);
>     }
>   return 0;
> }

Just to verify.  This is the correct testcase:

[hjl@gnu-6 orphan-4]$ cat app.c
#define _GNU_SOURCE
#include <stdio.h>
#include <dlfcn.h>

extern int __start___verbose[];
extern int __stop___verbose[];
int bar (void)
{
  static int my_var __attribute__((section("__verbose"))) = 6;
  int *ptr;
  ptr = (int*) dlsym(RTLD_DEFAULT, "__start___verbose");
  if (!ptr || *ptr != 6)
    return -1;
  return 0;
}

int main()
{
  if (bar () != 0)
    {
      printf("main: wrong __start___verbose\n");
      return 2;
    }
  return 0;
}
[hjl@gnu-6 orphan-4]$ make
cc -g   -c -o app.o app.c
cc -B./ -o app app.o -ldl -Wl,-R,.
./app
main: wrong __start___verbose
make: *** [Makefile:6: all] Error 2
[hjl@gnu-6 orphan-4]$

Thanks.

-- 
H.J.