FIX: /Og Causes C1001 While Looping

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

      - Microsoft Visual C++, 32-bit Editions, version 5.0
  

SYMPTOMS

Compiling code similar to the code in the sample below may cause the following error to be generated:

   fatal error C1001: INTERNAL COMPILER ERROR
       (compiler file 'E:\utc\src\\P2\main.c', line 379)

RESOLUTION

One way to work around the C1001 error is to correct the apparent programming error in the sample code below. Notice the check of p==0 in the if statement. The code that follows will cause an access violation if executed. Changing the check to p!=0 will cause the compiler to not generate the C1001 error and allow the code to compile. Another workaround that preserves the apparently incorrect algorithm is to introduce a local integer that holds the result of the comparison of p to zero. Use this local integer in the if statement instead of the actual comparison.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been fixed in Visual Studio 97 Service Pack 3.

For additional information about the Visual Studio 97 Service Pack 3, 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

   // compile options: /Og /c
   int f( int * p )
   {
      int i = 1;
      // int i2 = (p==0); // uncomment these 2 lines and
      // if( i2 )         //
      if( p == 0 )        // comment this one for workaround
      {
         while( i && *p != 0 )
         {
            i = *p++ == 3;
         }
      }
      return i;
   }