In C++, is this:
#ifdef A && B
the same as:
#if defined(A) && defined(B)
I was thinking it wasn't, but I haven't been able to find a difference with my compiler (VS2005).
They are not the same. The first one doesn't work (I tested in gcc 4.4.1). Error message was:
test.cc:1:15: warning: extra tokens at end of #ifdef directive
If you want to check if multiple things are defined, use the second one.
You can use the defined operator in the #if directive to use expressions that evaluate to 0 or 1 within a preprocessor line. This saves you from using nested preprocessing directives. The parentheses around the identifier are optional. For example:
#if defined (MAX) && ! defined (MIN)
Without using the defined operator, you would have to include the following two directives to perform the above example:
#ifdef max #ifndef min