[ollien]

> The issue with 1 is that it only works until you pass an array into a function by pointer, then the macro no longer works. GCC even has a warning for this.

Even worse, even if you specify the argument to be "of the type" array, it will actually still decay to a pointer. Basically, this macro will only work if you use it in the same function the array is defined.

https://godbolt.org/z/vr4za73qq

[uecker]

You need to pass a pointer to an array: https://godbolt.org/z/jYzY79ac4

When passing an array it decays into a pointer and the size is lost. We can also change sizeof to recover it, but there was a proposal for a _Lengthof operator which could work here.

[bheadmaster]

One exception is if you explicitly define argument as array of fixed length.

Downside being, obviously, that it will only work with arrays of that particular length.