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Re: GCC 3.4 and glibc/nptl: Cancellation broken

On Thu, Jan 22, 2004 at 04:23:37PM +0100, Andreas Jaeger wrote:
> On both i686 and amd64 (no other platforms tested) the current CVS
> glibc with nptl enabled does not pass the nptl testsuite when compiled
> with GCC 3.4 CVS.  The failing tests include:
> tst-cancelx{4,5,10,11,12,14,15,16,17,18,20,21}
> tst-cleanupx{0,1,3,4}
> Note that the tests without the 'x' work.  AFAIK the only difference
> between them is the usage of -fexceptions for the ones with the x.
> On AMD64 I get the following (i686 is equivalent) backtrace for
> nptl/tst-cleanupx0:
> The problem seems to be that the unwind functions are both in the
> executable image and in libgcc_s which is loaded by glibc (via
> dlopen).
> The actual problem then is that the called _Unwind_ForcedUnwind is
> From gcc_s and initializes its static dwarf_reg_size_table.  But later
> the _Unwind_SetGR in the executable is called from the personality
> routine which looks at its own static dwarf_reg_size_table - and this
> one was never initialized and this leads to the abort.  
> The unwind functions in the executable come from libgcc_eh.a and those
> From libgcc_s are dynamically loaded.
> Note this works with GCC 3.3.
> How is this supposed to work properly - and why does it work with 3.3
> but not with 3.4?

GCC 3.3 did not have the HPUX bloat in it.
One way to get around this quickly could be to:

-  size = dwarf_reg_size_table[index];
   ptr = context->reg[index];

+  if (sizeof (_Unwind_Ptr) == sizeof (_Unwind_Word))
+    return * (_Unwind_Word *) ptr;
+  size = dwarf_reg_size_table[index];
   /* This will segfault if the register hasn't been saved.  */
   if (size == sizeof(_Unwind_Ptr))
     return * (_Unwind_Ptr *) ptr;

   if (size == sizeof(_Unwind_Word))
     return * (_Unwind_Word *) ptr;

   abort ();

in _Unwind_GetGR and similarly with _Unwind_SetGR.

Another temporary solution can be linking all NPTL -fexceptions C
programs with -shared-libgcc for the time being.

As soon as I implement (or anyone else beats me to do it)
GCC driver should link all non-static binaries with:
--start-only-if-used -lgcc_s --end-only-if-used
and things will work just fine.


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