Q30644: Trapping FP Execptions with In-Line 8087 Code

Article: Q30644
Product(s): See article
Version(s): 5.00 5.10 | 5.10
Operating System(s): MS-DOS | OS/2
Keyword(s): ENDUSER | docerr | mspl13_c
Last Modified: 27-OCT-1988

Problem:

I am following the instructions on Pages 167-68 of the "Microsoft C
Optimizing Compiler User's Guide" to generate true in-line 8087 code.
I can link a module to remove the fixups for the interrupts, but I can
no longer handle floating-point exceptions using the signal function.

Response:

This is a documentation error. To trap floating-point exceptions with
the signal function while having true in-line 8087 code, you need to
add the following instructions to your FIXUP.ASM module:

           extrn __fpmath:far
           extrn __fptaskdata:far
           extrn __fpsignal:far

           CDATA   segment word common 'DATA'
                   dw      0
                   dd      __fpmath
                   dd      __fptaskdata
                   dd      __fpsignal
           CDATA   ends

Without the previous code, the start-up code will not initialize
the emulator and the signal function returns an error when you attempt
to use signal to trap floating-point exceptions.

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