Differences between release and debug builds
I used the phrase 'debug build' quite a few times in the preceding paragraphs. It's important to understand that asserts are a debug helper. If you're building a debug version of your program the compiler includes all the code inside the ASSERT(...). If you're building a release version the ASSERT itself and all the code inside the parentheses disappears. The assumption is that you've tested your debug builds and caught all likely errors. If you're unlucky and missed an error and release a buggy version of your program the hope is that it'll limp along even though it failed a test that an assert would have caught. Sometimes optimism is a good thing!
It might happen that you want, in a debug build, to assert that something is true and the something you're asserting is code that must be compiled into your program whether it's a debug build or a release build. That's where the VERIFY(...) macro comes to the rescue. VERIFY in a debug build includes the extra plumbing MFC provides to let you jump into the debugger in the event that the condition isn't satisfied. In a release build the extra plumbing is omitted from your program but the code inside the VERIFY(...) statement is still included in your executable. For example.
VERIFY(MoveFile(szOriginalFilename, szNewFileName));
will cause a debug assert if, for whatever reason, the MoveFile() function fails in debug builds. Regardless of what kind of build the MoveFile() call will be included in your program. But in a release build the failure of the call is simply ignored. Contrast this with
ASSERT(MoveFile(szOriginalFilename, szNewFileName));
In debug builds the MoveFile() will be compiled and executed. In release builds the line completely disappears and no file move is attempted. This can lead to some puzzled head-scratching
thanks
