For beginner Visual C++ programmers, an assertion error can be an unpleasant surprise
and the response to them is usually not clear. An assertion error is usually the result of
an MFC ASSERT macro. See the documentation for
for details about it .
MFC uses ASSERT macros extensively. If a problem exists in your program that MFC
uses an ASSERT macro to detect then the ASSERT macro in a debug version of your
program will result in a message box with "Abort", "Retry" and "Ignore" buttons.
If you click "Retry" then the debugger will show you were the error occurred.
The source code you see will probably be a line of MFC source code but you can
easily get the debugger to show you your source code and the line of your
program that the problem was encountered at.
The purpose of most ASSERT macros in MFC code is to test for conditions that might be a problem, or will be a problem,
if the program were allowed to continue. If you attempt to ignore
and/or bypass the assertions then more serious errors are likely to occur. The
appropriate response is to look at the MFC source code line containing the ASSERT macro to
see what the condition is that MFC is concerned about. Often there are also comments
indicating the problem and/or solution. To find the MFC source code line containing the ASSERT macro, debug the program, if you
have not already. Then when the assertion failure occurs, choose to debug the
program (click "Retry"). The debugger should show the MFC source code with the ASSERT macro.
You will probably need to know where in your own source code that the program
is. You can use the
call stack to find it. See: Debugging using the Call Stack.
It seems that 90% of the time that people post a question in a newsgroup or
discussion forum asking for help with an "assertion failure" or
something like that they just say that the program is getting an "assertion failure" or
something like that. Unfortunately it is not likely that anyone can be of much
assistance with such minimal information. If you have looked at the MFC
source code that is doing the assert and need help, then please be sure to
describe the MFC
source code that is doing the assert, and include relevant comments in the
MFC source code. Also include the line of you source that is getting the
assertion error and relevant previous lines.