PRB: midiInputHandler GP faults in MIDIMON Sample Application

The information in this article applies to:

• Microsoft Windows Software Development Kit (SDK) for Windows versions 3.0 and 3.1

SYMPTOMS

In the MIDIMON sample application provided with Visual C++ and the Microsoft Windows Software Development Kit (SDK) version 3.1, the midiInputHandler() callback function causes a general protection (GP) fault.

CAUSE

The GP fault occurs when the MIDI event handler tries to store event data in a static variable, but the data segment (DS) is not set correctly because the exported functions in the callback dynamic-link library (DLL) are not exported correctly.

RESOLUTION

Because the /GD compiler option is specified in the makefile for MIDIMON's callback DLL, the DLL's exported functions must be declared with the __export keyword. The exported functions missing the __export keyword are _WEP(), midiInputHandler(), and PutEvent(). The __export keyword should be added as required in CALLBACK.H and CALLBACK.DEF.

MORE INFORMATION

The problem described above exists only in the version of MIDIMON distributed with Visual C++ (Microsoft C version 8.0); the original version distributed with C 7.0 builds correctly as shipped.