Some special usage of C language (# define)

I haven't written a BLOG for a long time. ^_^

If you don't know what to write, write something that is easy to ignore.

I. 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.

Author: vonger