- Macros are text replacements created with #define that insert code into your program. Macros may take parameters like a function, but the macro code and parameters are always inserted into code by text substitution.
- Are evaluated by the preprocessor
- Are not executable code themselves
- Can control the generation of code before the compilation process
- Provide shortcuts
#define label text
- Every instance of label in the current file will be replaced by text
- text can be anything you can type into your editor
- Arithmetic expressions evaluated at compile time
#define label(arg1,…, argn) code
- The code must fit on a single line or use '\' to split lines
- Text substitution used to insert arguments into code
- Each instance of label() will be expanded into code
- This is not the same as a C function!
Extreme care must be exercised when using macros. Consider the following use of the below macro:
The result will be the following:
x = 30
i = 7
x = square(i++);
x = ((i++)*(i++));
So i gets incremented twice, not once at the end as expected.