what's the mechanism of sizeof() in C/C++?

Question

It seems sizeof is not a real function?

for example, if you write like this:

int i=0;
printf(\"%d\\n\", sizeof(++i));
printf(\"%d\\n\", i);
         


        

Answer 1

It is replaced with the constant (4 in your case) at compile time. Because it takes 4 bytes to hold an int on your platform.

And your code will not compile, instead of giving you any output ;-) Because of sizoef ;-)