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Re: [patch]: Replace stryoul call to fetch address
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...
> 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. ;-)
>> 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.
> 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. ;-)
>
>> We'll need a way to distinguish Cygwin vs native Windows
>> binaries. Probably by checking for cygwin.dll in the dll import list?
>
> A check for cygwin1.dll is already done in windows_make_so.
Yeah, though that's only after the dll is loaded. I was thinking
of looking at import list, when the executable is loaded in gdb,
hence before the program is run.
>
>> Another point where that'd be good is in step-over-longjmp support
>> (gdbarch_get_longjmp_target). IIRC, the offset of PC within
>> the jmpbuf of msvcrt.dll is not the same as Cygwin's (32-bit;
>> dunno about 64-bit).
>
> Cygwin 64 bit uses the same jmpbuf layout as native Windows. Only
> two members are used differently, but those should not be used by
> GDB anyway.
OK.
> Ok, I apply it then with only the int changed to unsigned.
Thanks.
--
Pedro Alves