FIX: System Hang with /Oe Option and Switch Statements

The information in this article applies to:

• The Microsoft C/C++ Compiler (CL.EXE), included with:

      - Microsoft Visual C++ for Windows, version 1.0
  

SYMPTOMS

When compiling a source module, the C/C++ compiler may cause the system to hang and not respond if all of the following conditions exist:

1. The code is being compiled with the /Oe (Enable Global Register Allocation) optimization.

2. The source code contains a switch statement where the switch expression contains a function call. For example:

          switch ( my_fcn( 100 ) ) { ... }
   

3. The same function that contains the switch statement has a call to setjmp().

RESOLUTION

To work around the problem, change the switch statement so the switch expression does not contain a function call. Alternatively, avoid using /Oe when compiling the module, or use the #pragma optimize() directive to disable /Oe for the function with the switch statement. For example, place the following statement before the function containing the switch statement:

    #pragma optimize( "e", off ) // Disables /Oe

    #pragma optimize( "", on )   // Re-enables /Oe

STATUS

Microsoft has confirmed this to be a problem in the C/C++ compiler for MS-DOS version 8.0. This problem was corrected in the C/C++ compiler for MS-DOS version 8.0c, included with Visual C++ for Windows, version 1.5.