Q69348: CVP May Generate a Trap B with Large Programs Under OS/2 1.30
Article: Q69348 Product(s): See article Version(s): 2.20 2.30 3.00 3.10 3.11 Operating System(s): OS/2 Keyword(s): ENDUSER | gp fault protection violation | mspl13_basic Last Modified: 25-FEB-1991 Debugging a large application with CodeView under OS/2 version 1.30 may result in a Trap B system error. Trap B is a "segment not present" exception, which results from changes that were made to this version of the operating system. In version 1.30 of OS/2, the code for DosPTrace() was made swappable, while in previous versions it was not. DosPTrace() is part of the OS/2 API that allows a parent process to control the execution of a child process, and to access the child process's memory directly to insert breakpoints or change data. Because CodeView relies heavily on DosPTrace(), problems arise if this code is swapped from memory. The majority of problems occur when execution reaches a breakpoint while the DosPTrace() code is not present; control should then jump to code that is not currently in RAM. Because large programs (or heavily loaded systems) tend to result in more swapping, this problem appears much more readily when debugging large applications. The only sure workaround for this problem is to turn off swapping while debugging, but it also may help to increase or free up available memory. To disable swapping, modify the MEMMAN switch in CONFIG.SYS as follows: MEMMAN=NOSWAP To increase available memory, either install more memory in the computer itself or terminate all other unnecessary processes before debugging (to remove them from memory). This problem is the result of a design change with OS/2 1.30 and is not a problem with CodeView. This change is being reconsidered for future versions of OS/2. New information will be posted here as it becomes available.
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