Re: [9fans] GUI toolkit for Plan 9

[Mike Haertel <mike@ducky.net>]

 From 9fans-admin@cse.psu.edu Tue Feb 26 11:06:34 2002
From: presotto@plan9.bell-labs.com
To: 9fans@cse.psu.edu
Subject: Re: [9fans] GUI toolkit for Plan 9
Date: Tue, 26 Feb 2002 14:05:49 -0500

>However, it seems to be an
>accepted consequence amongst compiler writers to trade off
>possible incorrect code generation against probable speed
>gains.  I've been burned numerous times by upping the optimization
>level in compilers including gcc.  This is not a new development.
>It was just as true 30 years ago with the fortran and PL1 compilers
>I used.

I'm not convinced that it's necessarily the compiler writers at
fault in many of these cases.  Certainly there are compiler and
optimizer bugs, and probably the more optimization you apply the
more likely you are to tickle these bugs.  You can blame the compiler
for those.

But, at least in the case of C, there are numerous cases where
people write code that is semantically undefined according to the
detailed rules of the C standard, but does what they want under
particular compilers or levels of optimization.  (E.g. how many of
you have assumed that local variables not declared volatile will
hold their values across a longjmp?)

So who to blame?  The compiler writer, who assumes the code being
compiled is standards-conforming?  The standards committee, who get
to decide which programming idioms will have defined behavior?
The programmer, who often doesn't really understand the rules of
the language?  The authors of programming textbooks, who often
downplay or omit these issues entirely?