Baffled by part of an assert function condition :)

Hi there!

Check this out:

Code:

---

m4xMsaaQuality = msQualityLevels.NumQualityLevels;
assert(m4xMsaaQuality > 0 && "Unexpected MSAA quality level.");

---

The variable m4xMsaaQuality is just an unsigned integer that records the available quality levels for a given display adapter and specified format. Just a number.

And it should be above zero. So I can understand the first part of the assert condition, but just not the second part with the string? It looks to me like the string is just a temporary variable created there and then and isn't even linked to a defined variable so I don't understand what checking it is doing?

Surely if I just create a temp variable like that in a condition check it will always simply return as true because it exists?

Thanks :)

Recall that a string constant has a type of 'const char *'

And all string constants will compare as not equal to NULL.
A pointer in a boolean context is implied as comparing it with NULL.
So in other words
assert(m4xMsaaQuality > 0 && "Unexpected MSAA quality level." != NULL);

So you could regard the assert as being logically equivalent to
assert(m4xMsaaQuality > 0 && true);

But using a string gives you a super handy way of documenting the reason for the assert.

Oh that's snazzy! So if the assert fails you'd get a little error message telling you why too :) So it's just for convenience of documentation and error hunting and that's it! Thanks very much Salem :)