Re: Fwd: Re: [Meta?] Where do I post proposals/ideas?

[Adhemerval Zanella <azanella at linux dot vnet dot ibm dot com>]

On 08-01-2015 09:58, Soni L. wrote:
> Eh, I forgot to reply to the list...
>
>
> -------- Forwarded Message --------
> Subject:     Re: [Meta?] Where do I post proposals/ideas?
> Date:     Thu, 08 Jan 2015 09:49:51 -0200
> From:     Soni L. <fakedme+libc@gmail.com>
> To:     Adhemerval Zanella <azanella@linux.vnet.ibm.com>
>
>
>
> On 08/01/15 09:33 AM, Adhemerval Zanella wrote:
>> On 08-01-2015 07:06, Soni L. wrote:
>>>
>>> On 08/01/15 02:13 AM, Paul Pluzhnikov wrote:
>>>> On Wed, Jan 7, 2015 at 5:56 PM, Soni L. <fakedme@gmail.com> wrote:
>>>>
>>>>> This is my proposal/idea:
>>>> 1. What actual problem does your proposal solve?
>>>> 2. Are you aware of dlmopen ?
>>>>
>>>
>>> Oh great I derped when configuring that gmail alias >.>
>>>
>>> 1. It solves a problem when loading 2 different <Lua/Python/insert something else> versions where you can't load extensions. For example, if you load Python 2 and Python 3, you can make it so trying to load Python 2 modules works, but then you wouldn't be able to load Python 3 modules, or vice-versa.
>>>
>>> 2. `man dlmopen`: No manual entry for dlmopen
>>>
>> dlfcn/dlfcn.h :
>>
>> #ifdef __USE_GNU
>> [...]
>> /* Type for namespace indeces.  */
>> typedef long int Lmid_t;
>>
>> /* Special namespace ID values.  */
>> # define LM_ID_BASE     0       /* Initial namespace.  */
>> # define LM_ID_NEWLM    -1      /* For dlmopen: request new namespace.  */
>> [...]
>> /* Like `dlopen', but request object to be allocated in a new namespace.  */
>> extern void *dlmopen (Lmid_t __nsid, const char *__file, int __mode) __THROWNL;
>>
>> /* Find the run-time address in the shared object HANDLE refers to
>>     of the symbol called NAME with VERSION.  */
>> extern void *dlvsym (void *__restrict __handle,
>>                       const char *__restrict __name,
>>                       const char *__restrict __version)
>>       __THROW __nonnull ((2, 3));
>> #endif
>>
>
> Oh... And how do I use it?
>
>
>
$ cat dlmopen_test.c
#define _GNU_SOURCE

#include <dlfcn.h>
#include <link.h>
#include <stdio.h>
#include <stdlib.h>

typedef void (*foo_t)(void);

int
main (int argc, char **argv)
{
  const char lib_string[] = "dummy.so.1";

  void *handle1 = dlmopen (LM_ID_NEWLM, lib_string, RTLD_LOCAL | RTLD_LAZY);
  if (handle1 == NULL)
    {
      printf ("error: dlmopen failed (1)\n");
      exit (EXIT_FAILURE);
    }
  printf ("handle1 = 0x%p\n", handle1);

  void *handle2 = dlmopen (LM_ID_NEWLM, lib_string, RTLD_LOCAL | RTLD_LAZY);
  if (handle1 == NULL)
    {
      printf ("error: dlmopen failed (2)\n");
      exit (EXIT_FAILURE);
    }
  printf ("handle1 = 0x%p\n", handle2);

  foo_t foo1 = (foo_t) dlsym (handle1, "foo");
  if (foo1 == NULL)
    {
      printf ("error: dlvsym failed (1)\n");
      exit (EXIT_FAILURE);
    }
  foo_t foo2 = (foo_t) dlsym (handle1, "foo");
  if (foo1 == NULL)
    {
      printf ("error: dlvsym failed (2)\n");
      exit (EXIT_FAILURE);
    }

  foo1 ();
  foo2 ();

  dlclose (handle1);
  dlclose (handle2);

  return 0;
}

$ cat dummy.c 
#include <stdio.h>

void foo(void)
{
  printf ("foo\n");
}

$ cat Makefile 
CC=gcc
CFLAGS = -g -Wall

all: dlmopen_test

dlmopen_test: dlmopen_test.c dummy.so.1
	$(CC) $< $(CFLAGS) -ldl -o $@

dummy.so.1: dummy.o
	$(CC) $< $(CFLAGS) -shared -o $@

dummy.o: dummy.c
	$(CC) $< $(CFLAGS) -fPIC -c -o $@

.PHONY: clean

clean:
	rm -f dlmopen_test *.o dummy.so.1

$ make
gcc dummy.c -g -Wall -fPIC -c -o dummy.o
gcc dummy.o -g -Wall -shared -o dummy.so.1
gcc dlmopen_test.c -g -Wall -ldl -o dlmopen_test

$ LD_LIBRARY_PATH=. ./dlmopen_test
handle1 = 0x0xd12030
handle1 = 0x0xd132b0
foo
foo