What is the difference between a macro and a function in C? [closed]

Question

What is the difference between a macro and a function in C? Please tell me one application where I can use macros and functions?

Answer 1

The basic difference is that function is compiled and macro is preprocessed. When you use a function call it will be translated into ASM CALL with all these stack operations to pass parameters and return values. When you use a MACRO, C preprocessor will translate all strings using macro and than compile.

Minus of using macros is that they hide implementation. Its way harder to find bug if have one.

Answer 2

In C (and C++) a macro is a preprocessor directive. This means that before your program starts compiling it will go through and process all your macros. Macros are useful because

• They can make your program easier to read
• They can improve efficiency (as they can be calculated at compile time)
• They can shorten long or complicated expressions that are used a lot. For example, we use a macro to get the current log4cpp logger and another few to write to it with various levels.

Disdvatages

• Expand the size of your executable
• Can flood your name space if not careful. For example, if you have too many preprocessor macros you can accidentally use their names in your code, which can be very confusing to debug.

Example

#define INCREMENT(x) x++

A function is a piece of code that can relatively independently be executed and performs a specific task. You can think of it sort of like a mathematical function: a function given a set of inputs will give a particular output. In C these are defined as

<return type> <name>(<parameters>)
{
  //code body
}