FIX: Global Optimizations (/Og) May Cause the Compiler to Hang

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

SYMPTOMS

The compiler hangs when you are building a function that contains many expressions involving floating-point operations and the /Og optimization is enabled.

RESOLUTION

Disable global optimizations for the file that is causing the compiler to hang. You can do this with either #pragma optimize("g",off) or by using the /Og- switch.

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:

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

MORE INFORMATION

The following sample reproduces the problem. Other examples of this problem are too large to demonstrate in a small sample.

Sample Code

    // Compile options: /c /Og
    float f(int i)
    {
      switch(i)
      {
      case  1: return ( 1.1f * i );
      case  2: return ( 2.2f * i );
      case  3: return ( 3.3f * i );
      case  4: return ( 4.4f * i );
      case  5: return ( 5.5f * i );
      case  6: return ( 6.6f * i );
      case  7: return ( 7.7f * i );
      case  8: return ( 8.8f * i );
      }

    return(2.0f*i);
    } 

Additional query words: /O2 Release Maximum Speed

Keywords : kbcode kbtool kbCompiler kbVC500bug kbVS97sp1fix
Version : 5.0
Platform : NT WINDOWS
Issue type : kbbug