C++ standards question
Thu Feb 7 08:02:00 GMT 2013
I haven't tried constructing a small test case. I fixed the problem by
if ( expression of *p ) *((char volatile*)p) = '-';
I am a skilled enough asm programmer to have zero doubt that I correctly
interpreted the compiled code. It did have that "optimization".
I don't know what else in that C++ function might have given the
compiler permission to make that optimization. I don't think anything
did. I know there was no unconditional write to *p in C++ code and
there was an unconditional write to *p in the asm code.
> This sounds like a bug. But I am skeptical that any compiler has this bug. Do you have a small test case that demonstrates it? Compilers aren't bug-free (nothing is) but there are FAR more bugs in compiler input than compilers themselves.
> - Jay
> On Feb 3, 2013, at 9:34 PM, "Mailaripillai, Kannan Jeganathan" <email@example.com> wrote:
>>> if ( expression of *p ) *p = '-';
>>> The optimizer changes that to the equivalent of
>>> *p = (expression of *p ) ? '-' : *p;
>>> Is that a valid optimization?
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