Works exactly like the MFC macro VERIFY.
Specifies an expression (including pointer values) that evaluates to nonzero or 0.
In the debug version of your application, the ISAPIVERIFY macro evaluates its argument. If the result is 0, the macro prints a diagnostic message and halts the program. If the condition is nonzero, it does nothing.
The diagnostic message has the form
assertion failed in file <name> in line <num>
where name is the name of the source file and num is the line number of the assertion that failed in the source file.
In the release version of your application, ISAPIVERIFY evaluates the expression but does not print or interrupt the program. For example, if the expression is a function call, the call will be made.
ISAPI applications do not have to use MFC. If MFC is not linked to your application, ISAPIVERIFY provides the same VERIFY functionality. If your application is linked to the MFC, ISAPIVERIFY simply calls MFC's VERIFY.