This is the mail archive of the
gcc@gcc.gnu.org
mailing list for the GCC project.
Re: gcc 3.3 / i386 / -O2 question
On Wed, 17 Nov 2004, Steven Bosscher wrote:
> Remember, "Undefined behavior" is not the same thing as "Unspecified
> behavior". In the latter case, perhaps you're right. Unspecified
> behavior should be consistent independent of the compiler options
> (and this behavior should be documented). But for undefined behavior
> you shouldn't expect anything.
No, it's implementation-defined behavior that is documented. Unspecified
behavior has bounds of variation but need not be documented. For example,
in evaluating "x = f() + g()", the order in which f() and g() are
evaluated is unspecified and could vary with compiler options, but their
evaluation is not interleaved.
--
Joseph S. Myers http://www.srcf.ucam.org/~jsm28/gcc/
jsm@polyomino.org.uk (personal mail)
joseph@codesourcery.com (CodeSourcery mail)
jsm28@gcc.gnu.org (Bugzilla assignments and CCs)