Some special C language usage -------- [Badboy]

I. special string macro [cpp] # defineA (x) T _ # x # defineB (x) # @ x # defineC (x) # x we suppose x = 1, the macro definition above will be interpreted as follows: A (1) ------ & gt; T_1B (1) ------ & gt; & #39; 1 & #39; C (1) ------ & gt 1: special string macros

[Cpp]

# Define A (x) T _ # x

# Define B (x) # @ x

# Define C (x) # x

Assume that x = 1, the macro definition above will be interpreted as follows:

A (1) ------> T_1

B (1) ------> '1'

C (1) ------> "1"

These functions are mainly used in string processing functions and parameter naming. they are not complex, but few are known.

II. shielding useless parameter warnings

[Cpp]

# Define UNUSED_PARAM (p) (void) p)

This is used to block invalid parameters

For example

[Cpp] view plaincopy

Void a (int x1, int x2)

{

// Do nothing

}

A warning is displayed. x1 and x2 are invalid parameters.

However, it doesn't matter if you write it like this.

[Cpp]

Void a (int x1, int x2)

{

UNUSED_PARAM (x1 );

UNUSED_PARAM (x2 );

}

3: I can't think of it. I want to hold a place and wait until I wake up.

I will not write more common macro usage, such as the header file security macro, version definition macro, flexible use indeed get twice the result with half the effort.