This is the mail archive of the gcc-patches@gcc.gnu.org mailing list for the GCC project.

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]
Other format:	[Raw text]

Re: [PATCH][C/C++] Do not promote return arguments

From: Paolo Bonzini <bonzini at gnu dot org>
To: Andrew Haley <aph-gcc at littlepinkcloud dot COM>
Cc: Ian Lance Taylor <iant at google dot com>, Richard Guenther <rguenther at suse dot de>, gcc-patches at gcc dot gnu dot org
Date: Mon, 06 Aug 2007 17:07:51 +0200
Subject: Re: [PATCH][C/C++] Do not promote return arguments
References: <Pine.LNX.4.64.0707051311250.24708@zhemvz.fhfr.qr> <m3y7ht38al.fsf@localhost.localdomain> <18103.7341.556783.13690@zebedee.pink> <m3lkcou45e.fsf@localhost.localdomain> <18103.13400.127562.689237@zebedee.pink>

I don't think it breaks any standard C/C++ code, but the ABI allows
C/C++ code to be called from assembler (and other languages) and
defines how return values should be promoted.  It's quite proper for
assembly code to assume that return values are promoted according to
their type, and this is where the libffi breakage came from.

Also, non-portable C/C++code that assumes that short and char values
will be promoted to ints will be broken by this change.  Sure, it's
nonstandard C/C++ code, but according to the ABI it shouldn't break.
We don't know how much code of this kind there is.

I agree with Andrew, but OTOH I think that this is an i386 backend bug, previously masked by the C++ front-end.

Paolo

Follow-Ups:
- Re: [PATCH][C/C++] Do not promote return arguments
  - From: Andrew Haley

References:
- Re: [PATCH][C/C++] Do not promote return arguments
  - From: Andrew Haley
- Re: [PATCH][C/C++] Do not promote return arguments
  - From: Ian Lance Taylor
- Re: [PATCH][C/C++] Do not promote return arguments
  - From: Andrew Haley

Index Nav:	[Date Index] [Subject Index] [Author Index] [Thread Index]
Message Nav:	[Date Prev] [Date Next]	[Thread Prev] [Thread Next]