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Message-ID: <55623666.7060908@iki.fi>
Date: Sun, 24 May 2015 23:36:54 +0300
From: "Andris Pavenis (andris DOT pavenis AT iki DOT fi)" <djgpp AT delorie DOT com>
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To: djgpp AT delorie DOT com
Subject: Re: New GDB versions and DJGPP (Was: ANNOUNCE: DJGPP 2.05 beta 1)
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Reply-To: djgpp AT delorie DOT com

On 05/24/2015 12:24 PM, Eli Zaretskii (eliz AT gnu DOT org) wrote:
>> Date: Sun, 24 May 2015 11:17:27 +0300
>> From: "Andris Pavenis (andris DOT pavenis AT iki DOT fi)" <djgpp AT delorie DOT com>
>>
>>> So what and how goes wrong in the DJGPP build of GDB?  Can someone
>>> with enough free time step through the go32 initialization, and see
>>> what's wrong there?
>> Perhaps at least some hint could give GDB commit which caused that DJGPP port stopped to work (with
>> symptoms described earlier)
>>
>> https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=commit;h=9b409511d07fe375284701af34909fb539029caf
> Thanks!
>
> Actually, it seems bd265cd0bde9e045ab5946532449430b66fe91ad, which is
> a followup to the one you mentioned, is the bad commit.  It seems a
> simple case of misunderstanding the API conventions of our read_child
> and write_child.
>
> Can you try the patch below?  If it fixes the problem, I will push it.
>
> diff --git a/gdb/go32-nat.c b/gdb/go32-nat.c
> index f3966cd..852473b 100644
> --- a/gdb/go32-nat.c
> +++ b/gdb/go32-nat.c
> @@ -587,6 +587,13 @@
>     else
>       res = read_child (memaddr, readbuf, len);
>   
> +  /* read_child and write_child return zero on success, non-zero on
> +     failure; adjust the result value to that.  */
> +  if (res == 0)
> +    res = len;
> +  else
> +    res = -1;
> +
>     if (res <= 0)
>       return TARGET_XFER_E_IO;
>   
>
>
I can confirm that with this patch applied I git current GIT master version of GDB to work for DJGPP:
- same example program cc1.exe from my earlier gcc-4.8.4 build used
- no error messages about accessing process memory
- backtrace somewhat unreliable but mostly works

Some small build problems:
- perhaps it would be best to kill dos_noop() in gdb-ser32.c and add appropriate static functions 
instead (proptype of of one of them has changed in master branch, which caused compile error)
- got also DJGPP related compile error which is potentially related to latest changes, but I did 
not have time to check whether it so

Also: Tried also cc1.exe from my last gcc-5.1.0 build with about the same results as with gcc-4.8.4 
except that backtrace works sligthly worse.

Also: fails to read debug info from cc1.exe from gcc-6.0.0 20150506 snapshot build and complains 
about dwarf error (could not find abbrev number 115 ....)

cc1.exe used from each tests were from stage 3 compile which is built by stage2 compiler of the 
same version.

Andris