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Re: [C++ PATCH] Don't promote bitfields in last arg of __builtin_*_overflow_p

From: Martin Sebor <msebor at gmail dot com>
To: Jakub Jelinek <jakub at redhat dot com>, Jason Merrill <jason at redhat dot com>
Cc: Joseph Myers <joseph at codesourcery dot com>, Marek Polacek <polacek at redhat dot com>, gcc-patches at gcc dot gnu dot org
Date: Wed, 15 Jun 2016 20:24:40 -0600
Subject: Re: [C++ PATCH] Don't promote bitfields in last arg of __builtin_*_overflow_p
Authentication-results: sourceware.org; auth=none
References: <20160610190835 dot GF7387 at tucnak dot redhat dot com> <575B14F7 dot 3070907 at gmail dot com> <20160614083359 dot GA7387 at tucnak dot redhat dot com> <20160614101602 dot GB7387 at tucnak dot redhat dot com> <57603B38 dot 9080302 at gmail dot com> <20160615114756 dot GJ7387 at tucnak dot redhat dot com> <alpine dot DEB dot 2 dot 20 dot 1606151213230 dot 10211 at digraph dot polyomino dot org dot uk> <57616156 dot 6090103 at gmail dot com> <20160615195122 dot GP7387 at tucnak dot redhat dot com>

On 06/15/2016 01:51 PM, Jakub Jelinek wrote:

On Wed, Jun 15, 2016 at 08:08:22AM -0600, Martin Sebor wrote:

I like the idea of being able to use the built-ins for this, but
I think it would be confusing for them to follow subtly different
rules for C than for C++.  Since the value of the last argument


Here is incremental patch to the patch I've posted earlier today,
which doesn't promote the last argument of __builtin_*_overflow_p
and thus for bitfields it behaves pretty much like the C FE.


Looks fine to me.  The bit-field handling should be explained
in the manual.  Though useful, it's unusual enough that I don't
think people will expect it (there have been bug reports or
questions in the past about the C handling of bit-fields from
users familiar with the C++ semantics).

Martin

Follow-Ups:
- Re: [C++ PATCH] Don't promote bitfields in last arg of __builtin_*_overflow_p
  - From: Joseph Myers

References:
- [PATCH] Reject boolean/enum types in last arg of __builtin_*_overflow_p
  - From: Jakub Jelinek
- Re: [PATCH] Reject boolean/enum types in last arg of __builtin_*_overflow_p
  - From: Martin Sebor
- Re: [PATCH] Reject boolean/enum types in last arg of __builtin_*_overflow_p
  - From: Jakub Jelinek
- Re: [PATCH] Reject boolean/enum types in last arg of __builtin_*_overflow_p
  - From: Jakub Jelinek
- Re: [PATCH] Reject boolean/enum types in last arg of __builtin_*_overflow_p
  - From: Martin Sebor
- [PATCH] Reject boolean/enum types in last arg of __builtin_*_overflow_p (take 2)
  - From: Jakub Jelinek
- Re: [PATCH] Reject boolean/enum types in last arg of __builtin_*_overflow_p (take 2)
  - From: Joseph Myers
- Re: [PATCH] Reject boolean/enum types in last arg of __builtin_*_overflow_p (take 2)
  - From: Martin Sebor
- [C++ PATCH] Don't promote bitfields in last arg of __builtin_*_overflow_p
  - From: Jakub Jelinek

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