PRB: Misuse of ASSERT Causes Problems for MFC AppsLast reviewed: July 31, 1997Article ID: Q115086 |
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MS-DOS | WINDOWS | WINDOWS NTkbprg kbprb The information in this article applies to:
The information in this article is included in the documentation starting with Visual C++ 5.0. Look there for future revisions.
SYMPTOMSWhen you run the debug version of your MFC application, there are no problems. However, the release version of the same application crashes, returns incorrect results, and/or exhibits some other abnormal behavior.
CAUSEThis problem can be caused when you place important code in an ASSERT statement to verify that it performs correctly. Because ASSERT statements are commented out in a release build of an MFC program, the code does not run in a release build.
RESOLUTIONIf you are using ASSERT to confirm that a function call succeeded, consider using VERIFY instead. The VERIFY macro evaluates its own arguments in both debug and release builds of the application. Another preferred technique is to assign the function's return value to a temporary variable and then test the variable in an ASSERT statement. Both of these techniques are demonstrated below in the "MORE INFORMATION" section of this article.
MORE INFORMATIONExamine the following code fragment:
char *buf; ASSERT(buf = (char *) calloc( 20, sizeof(char) )); strcpy( buf, "Hello, World" ); free( buf );This code runs perfectly in a debug version of an MFC application. If the call to calloc() fails, a diagnostic message is displayed, which includes the file and line number. However, in a retail build of an MFC application:
char *buf; buf = (char *) calloc( 20, sizeof(char) ); ASSERT( buf != NULL ); strcpy( buf, "Hello, World" ); free( buf );Or, you can use VERIFY instead:
char *buf; VERIFY(buf = (char *) calloc(20, sizeof(char) )); strcpy( buf, "Hello, World" ); free( buf ); |
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