PRB: No Symbolic Information for Local Variables

• The Visual Workbench Integrated Debugger included with:
• Microsoft Visual C++ 32-bit Edition, versions 1.0, 2.0, 4.0, 5.0

SYMPTOMS

The Developer Studio integrated debugger may display incorrect values for the local variables in an application. This can occur when the application being debugged was compiled with optimizations on.

RESOLUTION

During the debugging process for your application, specify the /Od compiler option switch to disable optimizations.

MORE INFORMATION

The C/C++ compilers mentioned above make ample use of registers to store local variables. This is particularly true when optimizations are turned on. Therefore, information regarding local variable storage is not always available to the debugger.

The following code example demonstrates this behavior. If you compile this code with optimizations disabled (specify the /Od compiler option switch), the values of the local variables in the func1() function are correctly displayed after the code calls the func2() function. However, if you compile the code with optimizations (specify the /Ox compiler option switch), the values of the same local variables do not display correctly until the code executes the return statement from func2().

Sample Code

   /*
    * Compile options needed: /Ox
    */

   void func2(int *arg1, int *arg2, int *arg3)
   {
      *arg1 = *arg2 = *arg3 = 5;
   }

   int func1(int arg1)
   {
      int local1, local2;

      func2(&arg1, &local1, &local2);

      return arg1 + local1 + local2;
   }

   void main(void)
   {
      func1(1);
   }