Re: [patch]: Replace stryoul call to fetch address

[Corinna Vinschen <vinschen@redhat.com>]

On Feb 27 19:14, Pedro Alves wrote:
> On 02/27/2013 06:38 PM, Corinna Vinschen wrote:
> 
> >> IIRC, the matching Cygwin code that that special
> >> Cygwin signals handling was never implemented, or it was disabled
> >> on Cygwin, or some such, and that gdb bits is actually causing
> >> trouble -- see http://sourceware.org/ml/gdb-patches/2013-02/msg00122.html.
> >> We should just zap it all.
> > 
> > I don't know exactly.  Probably cgf would be able to answer this
> > better than me.  
> 
> I think I recall some email from him long about about the
> cygwin side of that, but he wasn't against removing these
> bits of on the gdb end in that url above, so...

Chris, ping?

> > In fact I have a SEGV right now which I still have
> > to investigate, but I'm working on GDB only as a side job.
> 
> Sure.  I just meant to point out that that's exactly the code
> you're touching.  ;-)

The SEGV occurs in exception.c, function throw_exception, though.
The `*current_catcher->exception = exception;' assignment crashes
because current_catcher->exception is NULL.  I don't understand yet
why it's NULL, and why the throw_exception function doesn't test
this before trying to write *current_catcher->exception.

> >> One thing that comes to mind is I think we'll need to have separate
> >> mingw64/cygwin64 osabis.  Currently, mingw 32/64 use
> >> GDB_OSABI_CYGWIN, and that limps along, but with LP vs LLP, that
> >> won't work.
> > 
> > Why not?  The only difference between the x86_64 Cygwin and Mingw ABI
> > is the sizeof long.  And that's noted in the dwarf debug info.
> 
> Not every use use of the target's "long" goes through the debug info.  I
> see uses of  gdbarch_long_bit and builtin_long in the expression
> machinery, for example in c-exp.y, for handling integer constants,
> or in eval.c, for type promotion.  x64's long is fixed to 32-bit
> in amd64_windows_init_abi.

Oh, hmm.  I didn't notice that.  So, well, maybe...

> > Apart
> > from a strange crash when trying to load stripped executables, I'm
> > using a x86_64 Mingw GDB to debug x86_64 Cygwin DLL and binaries.
> > I'm not sure this single difference justifies distinct OSABIs.
> 
> Sure, we'll limp along.  But there are cases that bypass debug info.
> A distinct OSABI seems like the proper mechanism to me.  Time
> will tell.  ;-)

...you're right.  I just don't know if I'm really the right person
to do that.

> [...]
> > Ok, I apply it then with only the int changed to unsigned.
> 
> Thanks.

Applied.


Corinna

-- 
Corinna Vinschen
Cygwin Maintainer
Red Hat