PRB: F12 Causes Hard-Coded Breakpoint Exception When Debugging

• The integrated debugger included with: - Microsoft Visual C++, 32-bit Edition, versions 1.0, 2.0, 2.1, 4.0, 5.0

SYMPTOMS

When debugging an application under Windows NT, pressing the F12 key when the debuggee (the application) has focus causes the integrated debugger to pause the debuggee and display a dialog with one of the following messages:

   Break caused by hard coded breakpoint instruction.

   User breakpoint called from code at <address>

CAUSE

When the F12 key is pressed and the application in focus is being debugged, Windows NT calls a function similar to DebugBreak(), which executes a hard coded breakpoint instruction. The integrated debugger then traps the exception generated by this instruction.

This behavior is intentional and occurs with other debuggers such as WinDbg from the Windows 32-bit SDK.

RESOLUTION

While there is no way to disable this functionality, it doesn't affect the application that's being debugged other than to pause debugging and change focus. You can continue debugging by pressing the F5 key.

This can be annoying if you have an application that heavily uses the F12 key, so you may want to temporarily assign another key to handle the F12 key functionality in your program when debugging.

STATUS

This behavior is by design.