[snip]
> > does not work correctly on some machines.
>
> Could you be more specific. On which machines for instance ?
Me, myself personally tested on Intel Celeron 733, OS WinXP.
Compiler used: gcc 3.2 mingw port for windows.
Also reported not to work on Sun machine although on some other computers
this works.
That mean sometimes this work and sometimes not :)
Depends on processor perhaps, because I've read asm output (I'm just a crap
when it comes to x86 asm reading but...):
// g++ -save-temps -O0 (to avoid overoptimizations when variable comparison
to itself is just replaced with some boolean constant)
There we have is_nan for floats -
.section .text$_ZN4math4geom6is_nanIfEEbRKT_,"x"
.linkonce discard
.align 2
.globl __ZN4math4geom6is_nanIfEEbRKT_
.def __ZN4math4geom6is_nanIfEEbRKT_; .scl 2; .type 32; .endef
__ZN4math4geom6is_nanIfEEbRKT_:
LFB29:
// function prologue
pushl %ebp
LCFI225:
movl %esp, %ebp
LCFI226:
movl 8(%ebp), %eax
movl 8(%ebp), %edx
// operations on stack, sweet
flds (%eax) // load the same
flds (%edx) // variable to 2 copr. registers
fxch %st(1)
fucompp // comparison (x != x), obviously
fnstsw %ax
andb $69, %ah
xorb $64, %ah
setne %al
andl $255, %eax // && std::numeric_limits<float>::has_quiet_NaN
popl %ebp // function epilogue
ret
Seems like this is not compilers fault. Correct me if I'm wrong. And as me
uses intervals lib and is_nan f-tion, specifically; I'm really concerned
about such problems. If workaround is needed and it's not so simple, perhaps
it could be separated from certain library and moved itself to
numeric_utility.hpp or something?
Respect,
Justinas V.D.
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