[vorbis-dev] Re: [vorbis] bug in glibc 2.1.2 and older
xiphmont at xiph.org
Mon Jun 26 12:37:45 PDT 2000
> I have solved this problem in the splay mp3 decoder with this:
> In the header:
> #if (__GNUC__ < 2 || ( __GNUC__ == 2 && __GNUC_MINOR__ < 91 ) )
> #warning "inline code disabled! (buggy egcs version)"
> #undef __NO_MATH_INLINES
> #define __NO_MATH_INLINES 1
Insufficient! The bug is *not* in the compiler. It is in the glibc headers.
I can make bleededing edge GCC break very easily with the bad glibc.
> #include <math.h>
> In the makefile:
> CXXFLAGS=@CXXFLAGS@ -fno-strength-reduce
> (Opt level is 2)
Not needed in vorbis. My code doesn't break in strength reduction (and this
option is only needed if you're doing non-ANSI 'optimizations' in your C)
> and in the excutable:
> Then it did work.
All you did was cause a shift in optimization that changed FPU stack usage,
giving the illusion of the problem going away. If you'd done none of that but
just a printf() of the value after the pow() it would also appear to have
fixed the bug (by forcing a float store, also reducing the stack usage).
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