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Debug code: assert or if-statement?

Russell · 2004-06-07T10:22:12

I usually use assert macros to validate my data at the beginning of a function. I was thinking about this situation. The asserts get turned off in a release build, so I am basically assuming that they will never fail (after being tested for a good while in debug mode), and they are only there to help find bugs more easily when I compile in debug mode. My question is, if I am already assuming that the asserts will never fail, then why not just put in an if-statement and leave it active in release code? My thinking here is that since it can be assumed that the asserts will never fail, the branch prediction will have no problem at all predicting the correct branch in the corresponding if-statement, so there is basically zero overhead involved (assuming the asserts were simple, as in the examples below), and even though the asserts should never fail, it would be nice for the code to do something besides halt the program in the rare event that an assert would have failed. Here is an example. Normally I might do something like this. int SomeFunction (int number) { assert(number >= 0); // <-- arbitrary asserts assert(number <= 9); // code here... } I am considering replacing that with something like this. int SomeFunction (int number) { if ((number >= 0) && (number <= 9)) { // code here... } else { // report error, return a special value, or whatever } } The first function looks a little cleaner to me, but I can think of situations in my code where I have used asserts, and even though the asserts never fail, there is a reasonable alternative to halting the program in the event that the asserts did fail. Maybe I am just using asserts where I should be using if-statements or exceptions. What is the correct way to handle this?

General and Gameplay Programming Programming

Started by Russell June 05, 2004 02:22 AM

11 comments, last by Russell 19 years, 10 months ago

dmikesell

157

June 07, 2004 09:32 AM

quote:Original post by antareus
The asserts are for conditions which should never arise, such as being passed a null pointer when the function then goes ahead and dereferences said pointer.

Depends on the level of the function. If it''s an API level function, I''d consider this an error and return a status (or throw something) to the caller.

Etnu

880

June 07, 2004 09:46 AM

asserts are mainly a debugging tool. If statements should be used for run-time checking (for example, to make sure that users didn''t enter a number that was out of bounds or an invalid string or whatnot).

Don''t use if statements for the sake of debugging.

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quorn

145

June 07, 2004 10:22 AM

quote:Original post by Etnu
Don''t use if statements for the sake of debugging.

You can turn debugging information on and off at runtime if you use if statements.

Debug code: assert or if-statement?

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