Macros vs. Functions

• Functions must have a type associated with their parameters.
• Macros do not have to have a type associated with their parameters.
• Functions have overhead associated with each call.
• Macros do not have any overhead.
• Functions behave correctly (i.e. as expected) no matter what the actual parameters are.
• Macros do not always behave as expected if the parameters are expressions.
• Functions can be as complicated as needed.
• Macros should be very simple and should NOT contain a loop. Many compilers will not accept macros with loops. Basically, if the macro can not be written in 1 line, it probably should be a function.
• Most (if not all) of the function's overhead can be eliminated by using the C++ inline facility.
• To make the macros behave, the programmer must force a type constraint and use a global variable. (See Foster Example 11-16 on page 602.)