c - Macro Expansion

Question

Basic question

#define A 5
#define B 10

#define C (A*B)


int var;
var = C;

so here how macros will be expanded, Is it

var = (5*10)

or

var = (50)

My doubt is on the macro expansion. If macros has some calculations (*,-,/,+) on all constant,then will marco is just a in line expansion or it will evaluate the result and post it

Answer 1

Macro expansion is always just a textual transform of the input source code. You should be able to see the code after the pre-processor (the part of the compilation that does the macro expansion) is done; this text is what the compiler proper then works on.

But many compilers do "constant folding" optimization during compilation, that will optimize 5 * 10 to 50 so that it doesn't need to be calculated at runtime.