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Re: dlclose not calling destructors of static variables.
- From: Christopher Faylor <cgf-use-the-mailinglist-please at cygwin dot com>
- To: cygwin at cygwin dot com
- Date: Mon, 1 Feb 2010 11:26:04 -0500
- Subject: Re: dlclose not calling destructors of static variables.
- References: <4B61732F.firstname.lastname@example.org> <4B62DDE6.email@example.com> <4B62F118.firstname.lastname@example.org> <20100129184514.GA9550@ednor.casa.cgf.cx> <4B66BF2F.email@example.com>
- Reply-to: cygwin at cygwin dot com
On Mon, Feb 01, 2010 at 11:46:55AM +0000, Andrew West wrote:
>On 29/01/2010 18:45, Christopher Faylor wrote:
>> On Fri, Jan 29, 2010 at 02:30:48PM +0000, Andrew West wrote:
>>> On 29/01/2010 13:08, Dave Korn wrote:
>>>> On 28/01/2010 11:21, Andrew West wrote:
>>>>> I seem to be having a problem with dlclose not calling the destructors
>>>>> of statically declared variables. I've attached a simple test case
>>>>> which I compile as follows;
>>>> Thanks for the report and the STC; this should work. I'll take a look
>>>> at it over the weekend or the start of next week if nobody else gets
>>>> there first.
>>> Thanks for looking into this, it looks a little more complex than I
>>> first thought.
>>> I've tried calling __call_exitprocs during dlclose ( after run_dtors
>>> for the unloading library ) just to see if I was thinking along the
>>> right lines. Unfortunately this didn't work as when the destructor is
>>> registered with atexit it isn't associated with the loaded library but
>>> with the main executable.
>>> Which brings me on to the bigger problem, the static variables are
>>> registered with atexit rather than with __cxa_atexit which seems to be
>>> a violation of the C++ standard (1).
>>> Worse still gcc isn't compiled with cxa_atexit enabled. So I assume
>>> the right course of action here is to enable __cxa_atexit in gcc, and
>>> then make sure __cxa_finalize gets called when the library is unloaded?
>> I agree with your assessment here. I've checked in a change which works
>> around the problem you've uncovered but it is not foolproof. It should
>> fix the immediate problem but, in the long run, I agree that gcc should
>> be emitting code which calls __cxa_atexit. Of course I have no idea
>> what the other ramifications of doing that might be. Hopefully Dave can
>> enlighten us.
>> This is in today's snapshot at http://cygwin.com/snapshots/ .
>I checked out the changes and it still crashed for me. Digging into it
>the destructor for testlib fell outside of dll_end ( m.AllocationBase +
>m.RegionSize ). On a whim I change m.AllocationBase to m.BaseAddress and
>that seemed to fix it for me! The destructor ran on dlclose and the
>testrunner.exe didn't segfault.
Could you clarify? Are you saying that your test case still failed?
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