Magical if-statement

If it's a floating point number with a NaN value then (foo != foo) and the code could go into the else block.

If it's a floating point number with a NaN value then (foo != foo) and the code could go into the else block.

I'm 90% certain that it was an into of some sort. It was pretty funny and

we both were like, yeah, this will not be mentioned in polite company

ever again :) .

Of course if it's C++ and someone has overloaded operator == then literally anything could happen.

Of course, one could have written #define foo rand() and #define bar time(0) to be particularly treacherous. Then it would make sense. Sort of.

Couldn't foo and bar also be declared volotile?

when x is a floating point number, if (x!=x) permits to check if x is NaN. This is terribly ugly .... but that's it

Couldn't foo and bar also be declared volotile?

Yeah, without volatile foo==foo compiles to pseudo-asm like:

int reg0 = read(&foo);
bool reg1 = compare( reg0, reg0 );

But with volatile, it would compile to something like:

int reg0 = read(&foo);
int reg1 = read(&foo);
bool reg2 = compare( reg0, reg1 );

So if the memory at &foo is constantly changing, the comparison could possibly be false.

However, that kind of code should probably never be written. Generally if your code contains volatile, then you have a bug

About the only place it's valid to see that keyword used, would be inside the implementation of std::atomic.

Couldn't foo and bar also be declared volotile?

I don't think I've ever used volatile in my entire coding career.