[MPlayer-dev-eng] Re: -mieee CFLAG missing on alpha (patch included)

Thomas Cort linuxgeek at gmail.com
Tue Nov 29 21:38:15 CET 2005


> I disagree. It may work, but it is the wrong way to fix it. The problem
> here probably is a division by zero that should be fixed in CVS already.

I disagree with you disagreeing ;) I tried the following one line C
program, which has a division by zero, with and without -mieee and got
a floating point exception in both cases: int main() {
printf("%d\n",1/0); return 0; } I also tried the following one line C
program, which has a floating point division by zero, with and without
-mieee and got "inf" as the output in both cases: int main() {
printf("%f\n",1.0/0.0); return 0; }

So you see, dividing by zero has the same result whether or not I use
the -mieee flag. Therefore, I question the validity of the your
statement that a division by zero FPE was fixed by adding a compiler
flag that has no effect on division by zero exceptions. I was
wondering if you could explain to me why exactly adding -mieee on an
alpha would be a bad solution?

I also tried the CVS version to check if the problem was indeed fixed
"in CVS", but the CVS version would not compile:

cc -c -I../libvo -I../../libvo -I/usr/X11R6/include -O4  -mcpu=ev56
-pipe -ffast-math -fomit-frame-pointer -D_REENTRANT
-D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64  -I.. -I../loader       -o
stream_dvd.o stream_dvd.c
stream_dvd.c: In function `dvd_parse_chapter_range':
stream_dvd.c:82: warning: passing arg 2 of `strtol' from incompatible
pointer type
stream_dvd.c: At top level:
stream_dvd.c:420: error: parse error before '*' token
stream_dvd.c: In function `dvdtimetomsec':
stream_dvd.c:423: error: `dt' undeclared (first use in this function)
stream_dvd.c:423: error: (Each undeclared identifier is reported only once
stream_dvd.c:423: error: for each function it appears in.)
make[1]: *** [stream_dvd.o] Error 1
make[1]: Leaving directory `/root/mplayer-playground/main/libmpdemux'
make: *** [libmpdemux/libmpdemux.a] Error 2

-Thomas Cort

PS: A longer explaination of -mieee with a mini-FAQ:
http://skarpsey.dyndns.org/alpha-lfs/#mieee




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