Spawned Processes Do Not Always Handle Signals Properly

ID: Q46383

5.10 6.00 6.00a 6.00ax 7.00 | 1.00 1.50

MS-DOS                      | WINDOWS

kbprg

The information in this article applies to:

The C Run-time (CRT), included with:

    - Microsoft C for MS-DOS, versions 5.1, 6.0, 6.0a, and 6.0ax
    - Microsoft C/C++ for MS-DOS, version 7.0
    - Microsoft Visual C++ for Windows, versions 1.0 and 1.5

In the following example, the CTRL+C signal is not handled as expected within the spawned process:

   /*Compile options needed: none
   */ 

   #include <stdio.h>
   #include <process.h>

   void main( void )
   {
       int err;

       err = system( "TYPE TEST.TXT | MORE" );

       printf( "Return from system: %d\n", err );
   }

If CTRL+C is pressed while the file is being typed, temporary files used by MORE to emulate pipes are left in the root of the current drive. The return value from the system does not indicate any problems.

This is a limitation of MS-DOS and the way child processes handle certain signals, not a problem with the C compiler. Interrupting an assembly language program that calls MS-DOS Interrupt 0x4B to spawn "COMMAND /c TYPE TEST.TXT | MORE" gives the same results.

Additional reference words: kbinf 5.10 6.00 6.00a 6.00ax 7.00 1.00 1.50 KBCategory: kbprg KBSubcategory: CRTIss Keywords : kb16bitonly

Last Reviewed: July 18, 1997