Hi,
Attached is a small demo program (demo.c).
With 32-bit mingw compilers (both mingw.org's 4.5.2 and mingw64's 4.6.3) the
output of that program differs, depending upon whether I build it
with -ffloat-store or not.
I've no problem with that - I think I understand what's going on.
To get the output I desire I build *with* -ffloat-store.
When I switch to 64-bit mingw64 compilers (I've tried both 4.6.3 and 4.7.0)
I get the desired output *without* having to invoke -ffloat-store.
And if I do invoke -ffloat-store, I still get the same output.
Why the different behaviour with the 64-bit compilers ?
And a second question:
Is -fno-float-store a valid option ?
I can find no documentation for it - yet using it on the command line does
not produce the "unrecognized command line option" error that I would expect
from an invalid option.
Cheers,
Rob
#include <stdio.h>
#define N 11
double x[N] = { 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0 };
int a[N], b[N], diff[N];
char *success_message = "ok 1 - lists are equal";
char *failure_message = "not ok 1 - lists are equal";
static void
print( int *v, char *title )
{
int i;
printf( "%s = [", title );
for( i = 0; i < N; i++ ) printf( "%2d ", v[i] );
printf( "] \n" );
}
static int
ok( int *v )
{
int i;
for( i = 0; i < N; i++ ) if( v[i] ) return 0;
return 1;
}
double divide1( double a, double b ) { return a/b; }
int divide2( double a, double b ) { return a/b; }
int convert( double a ) { return a; }
int
main( int argc, char **argv )
{
int i;
char *msg;
printf( "1..1\n" );
for( i = 0; i < N; i++ ) a[i] = convert( divide1( x[i], .1 ) );
for( i = 0; i < N; i++ ) b[i] = divide2( x[i], .1 );
for( i = 0; i < N; i++ ) diff[i] = a[i] - b[i];
print( a, "# a" );
print( b, "# b" );
print( diff, "# a - b" );
msg = ok( diff ) ? success_message : failure_message;
printf( "%s\n", msg );
return 0;
}
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