Is this a known bug of c89/VC6?

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Is this a known bug of c89/VC6?

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Is this a known bug of c89/VC6? - Jan. 17, '06, 6:26:44 PM

jluis

Posts: 13
Joined: Oct. 18, '05,
Status: offline

Hi,
This is a test meant to try to isolate a real problem.
In both cases below the if tests should always give != 0
but when the macro definition is used I get NaN == 0
Here are the outputs

1. gcc test_nanVC.c -o test_nanVC
test_nanVC
x_dir = 2147483648.000000 x_indir = NaN
x_dir = 0 x_indir = 41e00000
Case Dir - Not-Equal zero
Case Indir - Not-Equal zero

2. c89 test_nanVC.c
a.out
x_dir = 2147483648.000000 x_indir = NaN
x_dir = 0 x_indir = 41e00000
Case Dir - Not-Equal zero
Case Indir - Equal zero

Is this a know bug of MSVC6 (the compiler I have installed)?

Thanks

J. Luis

/* test_nanVC.c */
#define GMT_make_fnan(x) (((unsigned int *) &x)[0] = 0x7fffffff)

#include <stdio.h>

int main(int argc, char **argv) {
float x_indir, x_dir;

x_dir = ((unsigned int *) &x_dir)[0] = 0x7fffffff;

GMT_make_fnan(x_indir);
fprintf(stderr,"x_dir = %f\tx_indir = %f\n",x_dir, x_indir);
fprintf(stderr,"x_dir = %0x\tx_indir = %0x\n",x_dir, x_indir);

if (x_dir == 0)
fprintf(stderr,"Case Dir - Equal zero\n");
else
fprintf(stderr,"Case Dir - Not-Equal zero\n");

if (x_indir == 0)
fprintf(stderr,"Case Indir - Equal zero\n");
else
fprintf(stderr,"Case Indir - Not-Equal zero\n");

return(0);
}

Post #: 1

RE: Is this a known bug of c89/VC6? - Jan. 17, '06, 6:38:44 PM

markfunk

Posts: 623
Joined: Mar. 31, '03,
Status: offline

Looks like it.
Using VC7, I get:

x_dir = 2147483648.000000 x_indir = NaN
x_dir = 0 x_indir = 41e00000
Case Dir - Not-Equal zero
Case Indir - Not-Equal zero

(in reply to jluis)