BUG: Step-After-Return in CodeView "Hangs" in a Large Function

MS-DOS         | WINDOWS

The information in this article applies to:

• Microsoft CodeView for MS-DOS, versions 4.0, 4.01, and 4.1
• Microsoft CodeView for Windows, versions 4.0, 4.01, and 4.1

SYMPTOMS

Using the PR command (Stop After Return) on a large function, or on a function with long iterative loop, causes CodeView to appear to hang.

CAUSE

The PR command is inefficient when used on large functions because it is too slow. In the case of the example below, there is no activity. Locals and watch expressions do not get updated, and IP tracking is inactive. Furthermore, CTRL+BREAK, CTRL+C, AND CTRL+ALT+SYSREQ do not terminate the PR command because CodeView is receiving single step notifications fast enough that the system is likely not getting a chance to process them.

RESOLUTION

To work around this problem, refrain from using the PR command on large functions, or those with long iterative loops. Instead, set a breakpoint at the location you wish CodeView to stop, or move the cursor to that location and press F7 to Run-To-Cursor.

STATUS

Microsoft has confirmed this to be problem with CodeView for MS-DOS, versions 4.0, 4.01, and 4.1, and CodeView for Windows, versions 4.0, 4.01, and 4.1. We are researching this problem and will post more information in the Microsoft Knowledge Base as soon as it becomes available.

MORE INFORMATION

The sample code below may be used to reproduce the problem. After starting CodeView, enter these commands in the command window:

  g f
  p
  pr

Sample Code

/* Compile options needed:  /Zi
*/
   #ifdef _WINDOWS
   #include <windows.h>
   #endif

   void f(void);

   void main(void)
   {
    f();
   }

   void f(void)
   {
    int t;
    int x;

    for (t=32767; t>0; --t)
    {
     x = t;
    }
   }

   #ifdef _WINDOWS
   int WINAPI WinMain (HANDLE hInstance, HANDLE hPrevInstance,
                       LPSTR lpszCmdParam, int nCmdShow)
   {
    main();
    return( TRUE );
   }
   #endif