INFO: Handling Floating-Point Errors in C

• The C Run-time (CRT) included with: - Microsoft C for MS-DOS, versions 5.1, 6.0, 6.0a, 6.0ax - Microsoft C for OS/2, versions 5.1, 6.0, 6.0a - Microsoft C/C++ for MS-DOS, version 7.0 - Microsoft Visual C++ for Windows, versions 1.0, 1.5 - Microsoft Visual C++ 32-bit Edition, versions 1.0, 2.0, 2.1, 2.2, 4.0,

       4.1, 5.0
  

SUMMARY

With Microsoft C, floating-point error-handling routines may be written using the signal() function; however, "return" should not be used to go back to the calling process. If "return" is used, the floating-point state is left undefined.

Instead, use the setjmp() function to save the stack environment before each section of the calling process code that may potentially generate a floating-point error. In the error handler, use _fpreset() to reinitialize the floating-point package and longjmp() to return to the calling process.

WARNING: Neither the setjmp nor longjmp function is compatible with the C++ language.

The sample program on page 296 of the "Microsoft C/C++ Run-time Library Reference" that shipped with Microsoft C/C++ version 7.0 demonstrates the use of setjmp(), _fpreset(), and longjmp() to handle a floating-point error. The online help also provides samples for these functions.

The function setjmp() saves the environment (bp, si, di, sp, and ds registers) and return address in a buffer. The buffer is used by longjmp() to restore the environment.

Keywords          : CRTIss kbfasttip
Version           : MS-DOS:6.00ax,7.0; OS/2:5.1,6.00a; WINDOWS:1.0,1.5;  WINDOWS NT:1.0,2.0,4.0,4.1,5.0
Platform          : MS-DOS NT OS/2 WINDOWS
Issue type        : kbinfo