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Date: Thu, 1 Oct 2015 10:34:59 +0300
Message-ID: <CAA2C=vAdzu+ebq1mEsoqwkxJcYR+2EZdKJ3d5XxOZRCytL6z8w@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>
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On 9/27/15, Ozkan Sezer <sezeroz AT gmail DOT com> wrote:
> 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
>

PING? Any ideas? (Sorry that I brought the issue
but have no patch for it myself.)