Compilers: Principles and Practice by Pearson

Assemblers and Macro Processors 445

Macros and Subroutines

Seemingly, from the viewpoint of the programmer, macros provide the same kind of facilities as

subroutines. Then how do they compare?

Macro: Complete macro body code gets substituted every time it is used, so increases the code

length. As it is in-line code, save on the subroutine call and return instruction time and stack load

overheads, and thus works fast.

Subroutine: Code is included only once in the program. Time and stack-space overheads for each

call and return.

In summary, we can say that if the job can be done with a few instructions, say 5 to 10, then it may be

advisable to implement ...