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Re: [PATCH/expand] PR64011 Adjust bitsize when partial overflow happen for big-endian

From: Jeff Law <law at redhat dot com>
To: Joseph Myers <joseph at codesourcery dot com>
Cc: Jiong Wang <jiong dot wang at arm dot com>, "gcc-patches at gcc dot gnu dot org" <gcc-patches at gcc dot gnu dot org>
Date: Tue, 13 Jan 2015 22:30:45 -0700
Subject: Re: [PATCH/expand] PR64011 Adjust bitsize when partial overflow happen for big-endian
Authentication-results: sourceware.org; auth=none
References: <54A27CBA dot 8080609 at arm dot com> <54AF6B36 dot 5090305 at redhat dot com> <54AFD9F8 dot 5060202 at arm dot com> <54B59217 dot 5070305 at redhat dot com> <alpine dot DEB dot 2 dot 10 dot 1501132239540 dot 10473 at digraph dot polyomino dot org dot uk>

On 01/13/15 15:42, Joseph Myers wrote:

On Tue, 13 Jan 2015, Jeff Law wrote:

In many ways having the compiler or assembler spitting out an error here is
preferable to silently compiling the code.  That would also help explain why


As usual, an error is incorrect in such a case that only has undefined
behavior at runtime (but it may be compiled into an abort if the behavior
is unconditionally undefined, and the abort doesn't replace anything
before the undefined behavior that might have stopped the undefined
behavior from occurring).

You are, of course, correct. We can't error here, but we can generate aconditional warning.


jeff

References:
- Re: [PATCH/expand] PR64011 Adjust bitsize when partial overflow happen for big-endian
  - From: Jeff Law
- Re: [PATCH/expand] PR64011 Adjust bitsize when partial overflow happen for big-endian
  - From: Jiong Wang
- Re: [PATCH/expand] PR64011 Adjust bitsize when partial overflow happen for big-endian
  - From: Jeff Law
- Re: [PATCH/expand] PR64011 Adjust bitsize when partial overflow happen for big-endian
  - From: Joseph Myers

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