Re: [Plplot-devel] Re: New way of getting device info from dyndrivers

[Alan W. I. <ir...@be...>]

On Mon, 10 Feb 2003, Alan W. Irwin wrote:

> On Mon, 10 Feb 2003, Rafael Laboissiere wrote:
>
> > I can replicate this bug here.  The tkwin driver has probably some memory
> > management problems that make surface when lt_dlopenext/lt_dlclose are used.
> > That's weird, eh?
>
> I don't completely trust such interpretation....

I ran the valgrind test I suggested with lt_dclose uncommented and excluding
certain drivers.  This test was based on the 10 February software. The point
of this test is to look for memory management problems in the current set of
drivers with this old code rather than to look at the code Rafael just
checked in which (I believe) avoids making this test of
lt_dlopenext/lt_dlclose for every driver.

I found I got an absolutely clean valgrind result (except for well known
unfreed memory warnings at programme end) if I excluded xwin, tkwin, tk, and
gd.  Here was the list of drivers for the clean result:

ls ../../driversd/*.so
../../driversd/cgm.so*      ../../driversd/ljiip.so*
../../driversd/pstex.so*
../../driversd/dg300.so*    ../../driversd/null.so*    ../../driversd/tek.so*
../../driversd/hpgl.so*     ../../driversd/pbm.so*     ../../driversd/xfig.so*
../../driversd/impress.so*  ../../driversd/plmeta.so*
../../driversd/ljii.so*     ../../driversd/ps.so*

ldd shows that each of these is dynamically linked just to libplotd, libm,
libc, and libdl.  (cgm is also linked to the cd library, but that is a
static library so its a different case than gd, xwin, tkwin, and tk which
all are linked to extra dynamic libraries.)  If I added in gd, then I got
valgrind errors, but no segfault.  In a previous test with gd, xwin, and tkwin
(and tk?) we got segfaults.

There does seem to be a pattern developing that all drivers linked to extra
dynamic libraries have memory management problems of some kind that are
reported by valgrind.  I cannot draw a definitive conclusion from this, but
there is certainly the possibility that a libtool (libltdl) bug could be the
cause of this pattern, and I will certainly check gd, xwin, tkwin, and tk
again once a new version of libtool is released.  For now, though, it is
best to avoid lt_dlclose (which I think the latest code from Rafael does).
In this case (commented out lt_dlclose) we do get valgrind errors, but so
far (knock on wood for luck!) no segfaults have showed up.

I am completely sold on autotools as a convenient way to set up the
configuration of our software.  However, I am sure looking forward to the
day that autotools stabilizes!

Alan
__________________________
Alan W. Irwin
email: ir...@be...
phone: 250-727-2902

Astronomical research affiliation with Department of Physics and Astronomy,
University of Victoria (astrowww.phys.uvic.ca).

Programming affiliations with the Canadian Centre for Climate Modelling and
Analysis (www.cccma.bc.ec.gc.ca) and the PLplot scientific plotting software
package (plplot.org).

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