The following test case shows the failure when compiling with -ffast-math
gives a different result than when compiling with out it.
More explanation in the comments at the top of the file.
Cheers,
Erik
/*
** This file is in the Public Domain.
**
** This program demonstrates a bug in the -ffast-math option of the gcc
** armel compiler : gcc version 4.3.2 (Debian 4.3.2-1.1)
**
** This works as expected:
**
** > gcc -Wall -O3 gcc-test.c -o gcc-test && ./gcc-test
** min : 0.0000 max : 0.0000
**
** Compile with -ffast-math and things goes screwy.
**
** > gcc -Wall -O3 -ffast-math gcc-test.c -o gcc-test && ./gcc-test
** min : 99999.0000 max : 0.0000
*/
#include <stdio.h>
#define COUNT 10
#define test_max(x,y) ((x) < (y) ? (y) : (x))
#define test_min(x,y) ((x) > (y) ? (y) : (x))
int
main (void)
{ /* C Standard says static data gets initialized to zero. */
static float data [COUNT] ;
float max = -99999.0, min = 99999.0 ;
int k ;
for (k = 0 ; k < COUNT ; k++)
{ max = test_max (max, data [k]) ;
min = test_min (min, data [k]) ;
} ;
printf ("min : %12.4f max : %12.4f\n", min, max) ;
return 0 ;
}
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