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Re: dlclose not calling destructors of static variables.

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 .



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.

For what it's worth the small change is attached as a patch.


Attachment: dll_init.patch
Description: Text document

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