Chapter 6 pre-processor

Macro is text expansion. In reality, it can be expanded and written to discover errors..

6.1 do not ignore spaces in macro definitions.6.2 When a macro Is Not a function macro defining a function, 1. Enclose each parameter in brackets. 2. Enclose the entire expression. 3. Make sure that the macro parameters have no side effects # define max (A, B) (a)> (B )? (A) (B) max (big, X [I ++]). At this time, ++ may be calculated twice, resulting in side effects. Macros may have side effects due to auto-increment or decrement operations, and may also generate very large expressions.
Eliminate the side effects of if else: # define assert (e) \ (void) (e) | _ assert_error (_ file __,__ line __)))
6.4 macro is not a type definition # define T1 struct Foo * typedef struct Foo * t2
T1 a, B; // declaration is extended to struct Foo * a, B; B is not a pointer. T2 A, B;