FIX: Calling a Function Returning double May Not Pop FPU Stack

• The C/C++ Compiler (CL.EXE) included with: - Microsoft Visual C++, 32-bit Editions, version 5.0

SYMPTOMS

When you call a function that returns a double, from within a conditional, and build with /Od, the compiler does not pop the Coprocessor stack. This may cause a floating point stack overflow (0xc0000092), or later calculations involving the FPU to evaluate to -1.#IND00. The sample below demonstrates a form of this bug.

RESOLUTION

Enable global optimizations (/Og).

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been corrected in Visual Studio 97 Service Pack 1.

For additional information about the Visual Studio 97 Service Pack 1, please see the following article in the Microsoft Knowledge Base:

   ARTICLE-ID: Q170365
   TITLE     : INFO: Visual Studio 97 Service Packs - What, Where, and Why

MORE INFORMATION

Sample Code

   // Compile options needed: /Od
   #include <float.h>
   #include <stdio.h>
   double func()
   {
     return 1.0;
   }
   void main()
   {
      int i;
      double d=2.0;
      // uncomment the next line to unmask exception
      //_controlfp(_EM_OVERFLOW, _MCW_EM );
      for( i = 0; i < 10; i++ )
      {
         if( func() );
      }
      // outputs -1.#IND00
      printf("%f",d+d);
   }