Re: Ltdl and gcov

[Ralf Wildenhues]

Hello Thomas,

* Thomas Moulard wrote on Mon, Jul 27, 2009 at 11:43:24AM CEST:
> I am trying to integrate gcov into my buildchain but I ran into the
> following problem: if I compile my Autoconf/Automake/Libtool package
> using -fprofile-arcs and -ftest-coverage, the program produces a segv
> at the end of the execution.  This program load a ltdl plug-in, do a
> simple thing and unload it.
> 
> The problem only arrive when I compile with -fprofile-arcs,
> -ftest-coverage and if lt_dlclose is called to properly unload the
> plug-in.  If I do not call lt_dlclose it always works, if I do not use
> these two compiling flags it always work and Valgrind does not report
> any error.
> 
> When it fails, gdb and valgrind indicates that the program jumped to
> an invalid address in libc-start.c:252.
> 
> Last thing: when I tried to compile with test coverage support both my
> plug-in /and/ my loader were recompiled with that flag.

This sounds very much like a bug in libc, GCC coverage support, or the
interaction between the two.  If you can reproduce the issue while using
dlopen and dlclose directly (thus by-passing libltdl), then you have
proof that libltdl is not part of this issue.

My guess would be that coverage support is not suited for unloading
plugins.  Maybe you can get more information about this on the gcc-help
mailing list.

Cheers,
Ralf