[LLVMdev] C as used/implemented in practice: analysis of responses

[Smith, Kevin B]

Ø  I'm not making any of this up; there have been published cases of bugs creeping into code that had worked correctly

Ø  for years

The generated machine code may have implemented what the programmer intended.  However, the bugs were there all along
in that the program relied on undefined behavior.  The specified semantics of the programming language, or of LLVM IR since
that itself is a programming language is what the user (or FE that uses LLVM IR as its output) can rely on, nothing else.

Kevin B. Smith

From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at cs.uiuc.edu] On Behalf Of Russell Wallace
Sent: Wednesday, July 01, 2015 11:35 AM
To: Tim Northover
Cc: llvmdev at cs.uiuc.edu
Subject: Re: [LLVMdev] C as used/implemented in practice: analysis of responses

Why do you say spin? I'm not making any of this up; there have been published cases of bugs creeping into code that had worked correctly for years, without any change to the code itself, because a new version of GCC started applying a monkey's paw optimisation. That's the sort of thing that prompted the survey that started this thread.

On Wed, Jul 1, 2015 at 7:30 PM, Tim Northover <t.p.northover at gmail.com<mailto:t.p.northover at gmail.com>> wrote:
> But having programs miscompiled so that they silently fail, in many cases
> starting only years after the code in question was written, is very much not
> okay. That's far worse than documented portability problems.

When given a certain spin...

Tim.

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20150701/b629fbe0/attachment.html>