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GCC Compiler Bug
----------------
Reference: http://boudicca.tux.org/hypermail/linux-kernel/2000week05/0983.html
From: Johan Kullstam (kullstam@ne.mediaone.net)
Date: Thu Jan 27 2000 - 18:00:28 EST
Horst von Brand <vonbrand@sleipnir.valparaiso.cl> writes:
> My question in this vein would be the -fno-strength-reduce. The gcc bug
> that placed this in the kernel was in gcc-2.7.2, and was worked around in
> 2.7.2.3 by just making this option unconditional. Both 2.2.15pre4 and
> 2.3.41pre2 at least demand gcc-2.7.2.3 as minimal version.
just when you thought it was safe to go into the water...
strength-reduction is broken again in gcc-2.95.2 (aka the current
release). i'm not sure about what versions actually do work.
for fun, try this one out. cut and paste the program bug.c.
$ gcc -O2 bug.c -o b0
$ gcc -O2 -fno-strength-reduce bug.c -o b1
run b1. notice it finish immediately.
now run b0. notice how b0 never terminates (until you ^C it).
-- bug.c -----------------------------------------
static void bug(int size, int tries)
{
int i;
int num = 0;
while (num < size)
{
for (i = 1; i < tries; i++) num++;
}
}
int main()
{
bug(5, 10);
return 0;
}
-- bug.c -----------------------------------------
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