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Date: Sun, 27 Sep 2015 00:28:24 +0300
Message-ID: <CAA2C=vDSknbCKHzUA954weavLj16nXuDyP_Ggi+SmLJ_e-U_KA@mail.gmail.com>
Subject: Re: dlclose not removing dependency dxes
From: "Ozkan Sezer (sezeroz AT gmail DOT com) [via djgpp AT delorie DOT com]" <djgpp AT delorie DOT com>
To: djgpp AT delorie DOT com
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On 9/26/15, Juan Manuel Guerrero (juan DOT guerrero AT gmx DOT de) [via
djgpp AT delorie DOT com] <djgpp AT delorie DOT com> wrote:
> On Friday, September 25, 2015 at 7:21:47 PM UTC+2, Ozkan Sezer
> (sezeroz AT gmail DOT com) [via djgpp AT delorie DOT com] wrote:
>> On 9/25/15, Ozkan Sezer <sezeroz AT gmail DOT com> wrote:
>> > AFAICS, dlclose()ing of a dxe doesn't remove its dependency dxes along
>> > with it, which will result in unnecessarily occupied memory which may
>> > prove fatal upon multiple dlopen()/dlclose() of a dxe with deps.  This
>> > needs addressing.
>> >
>>
>> My last argument was inaccurate and misleading. Here's better:
>>
>> One has a.dxe and b.dxe; a.dxe depends on b.dxe.  Do dlopen a.dxe
>> and b.dxe is opened implicitly.  Do dlcose a.dxe, and b.dxe stays
>> open still occupying its memory.  The memory occupied by the unused
>> b.dxe might be needed by the app but will be unavailable to it.
>> Further dlopen calls for a.dxe will increment the refcount for b.dxe
>> which never gets decremented.
>
>
> Can you provide a minimal sample code to demonstrate the issue?
>
> Regards,
> Juan M. Guerrero
>

=======================================

$ cat 12.c
extern int my_func2();
int my_func1() {
  return my_func2();
}
$ gcc -c 12.c
$ dxe3gen -o a.dxe -P b.dxe -U 12.o
$ dxe3gen --show-exp a.dxe
_my_func1
$ dxe3gen --show-dep a.dxe
b.dxe

=======================================

$ cat 13.c
int my_func2() {
  return -1;
}
$ gcc -c 13.c
$ dxe3gen -o b.dxe 13.o
$ dxe3gen --show-exp b.dxe
_my_func2

=======================================

$ cat 11.c
#include <dlfcn.h>
#include <stdio.h>

void *my_dxe1;
int (*my_f)();

int main (void) {
  my_dxe1 = dlopen("a.dxe",0);
  if (!my_dxe1) {
    printf("dlopen() failed\n");
    return 1;
  }
  dlclose(my_dxe1);

  my_f = dlsym(RTLD_DEFAULT,"_my_func1");
  if(!my_f) {
    printf("a.dxe not loaded\n");
  }
  else {
    printf("a.dxe:my_func1(): %p\n",my_f);
  }

  my_f = dlsym(RTLD_DEFAULT,"_my_func2");
  if(!my_f) {
    printf("b.dxe not loaded\n");
  }
  else {
    printf("b.dxe:my_func2(): %p\n",my_f);
    printf("b.dxe:my_func2() returns: %d\n",my_f());
  }

  return 0;
}

$ gcc -Wall -W 11.c

=======================================

$ a.exe > a.log
$ cat a.log
a.dxe not loaded
b.dxe:my_func2(): 95830
b.dxe:my_func2() returns: -1