Sender: rich AT phekda DOT freeserve DOT co DOT uk
Message-ID: <3EABD66F.59393BFF@phekda.freeserve.co.uk>
Date: Sun, 27 Apr 2003 14:09:03 +0100
From: Richard Dawe <rich AT phekda DOT freeserve DOT co DOT uk>
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To: DJGPP workers <djgpp-workers AT delorie DOT com>
Subject: [Fwd: Bug 00314 -- div() still broken]
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Reply-To: djgpp-workers AT delorie DOT com

Ben Peddell wrote:
> 
> Richard Dawe wrote:
> 
>  > Hello.
>  >
>  > Ben Peddell wrote:
>  >> [snip]
>  >>
>  >> OK. GCC 3.2.1 has -fpcc-struct-return by default in DJGPP, whilst GCC
>  >> 3.2.2 has -freg-struct-return by default in DJGPP.
>  >> GCC 3.2.2 may need to be configured to make -fpcc-struct-return the
>  >> default, to maintain compatibility with the DJGPP 2.03 libraries. Or,
>  >> the libraries may need to be re-compiled for GCC 3.2.2, and marked as
>  >> such.
>  >>
>  >> These options are in `info gcc "Invoking GCC" "Code Gen Options"'
>  >
>  >
>  > After rummaging around a bit more:
>  >
>  > It's possible that 3.2.1 was broken. There were some ABI regressions
>  > in 3.2.1 that were fixed in 3.2.2:
>  >
>  > http://gcc.gnu.org/gcc-3.2/changes.html#3.2.2
> 
> This does not mention DJGPP.
> Linux is mentioned. However, it returns the same as DJGPP - structures
> in memory (with gcc 3.2).
> 
>  >
>  > PR/9506 is the one:
>  >
>  > http://gcc.gnu.org/cgi-bin/gnatsweb.pl?cmd=view%20audit-trail&pr=9506
>  >
>  > gcc defaults to using -fpcc-struct-return, but what does it actually
>  > use for 2.95.2 and 3.2.2?
>  >
>  > I've just looked at the gcc 2.95.2 sources and it looks like
>  > -fpcc-struct-return (i.e.: use memory) is the default there.
>  >
>  > The gcc 3.2.2 source seems to default to using registers. See the end
>  > gcc/config/i386/djgpp.h:
>  >
>  > /* Don't default to pcc-struct-return, because gcc is the only
>  > compiler,
>  >    and we want to retain compatibility with older gcc versions.  */
>  > #define DEFAULT_PCC_STRUCT_RETURN 0
> 
> I wonder where they got that from?
> Did they accidentally put that in the wrong target? What systems default
> to structures in registers? Watch for ABI bugs of this sort in them.
> 
> GCC 3.2 still had structures in memory, and it is supposed to have had
> an ABI change from the previous GCCs.
> 
>  > Why is this defined? I couldn't see a ChangeLog entry for djgpp.h.
>  > AFAICT this breaks backwards compatibility, i.e.: the opposite of
> what > the comment says.
>  > Is there something I'm missing?
>  >
>  > Thanks, bye, Rich =]
>  >

-- 
Richard Dawe [ http://www.phekda.freeserve.co.uk/richdawe/ ]