Q41220: Program Hangs the Second Time It Is Run Using an 80287

Article: Q41220
Product(s): See article
Version(s): 5.00 5.10
Operating System(s): MS-DOS
Keyword(s): ENDUSER | | mspl13_c
Last Modified: 16-MAY-1989

When compiling a program that uses signal() with an 80287 coprocessor,
the first time the program runs, everything works correctly. But if
run a second time, it hangs the computer.

This problem has been confirmed to be with the old 80287 coprocessors
and has been corrected in newer 80287 chips.

The example program in the "Microsoft C for the MS-DOS Operating
System: Run-Time Library Reference" manual on Page 280 locks up on the
second time the program is executed with an old 80287. The following
is an example:

#include <stdio.h>
#include <signal.h>
#include <setjmp.h>
#include <float.h>

int fphandler ();
jmp_buf mark;
double a = 1.0, b = 0.0, c;

main()
{
    if(signal(SIGFPE, fphandler) == (int(*) () ) -1)
     abort();

    if(setjmp(mark) == 0)
    {
     c = a/b;
     printf("Should never get here\n");
    }

    printf("Recovered from floating-point error\n");
}

int fphandler (sig, num)
int sig, num;
{
    printf("signal = %d subcode = %d\n", sig, num);
    _fpreset();
    longjmp(mark, -1);
}

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