Use of static in C Language

During the development process, we often need to define some static variables or functions. Let's talk about static in detail;

1. Modify Variables

When static is used to modify a variable, the visible range and lifecycle of the variable are doomed;

(1) When modifying global variables

Static int flag1 = 0;

Int flag2 = 0;

These two variables are stored in the global data zone. flag1 is only visible in this file, but not in other files. flag2 can be used in other files by declaring extern int flag2;

(2) When modifying a local variable

Void fun (void ){

Static int temp1;

Int temp2 = 0;

......................

Return;

}

In the function, temp1 is a local static variable, stored in the global data zone, and temp2 is a local variable and stored on the stack. However, as the function exits, the lifecycle of temp2 ends, however, temp1 is still valid, and only the visible range is within this function. When you enter this function again, any modifications to temp1 are made based on the previous modification, that is, temp1 has a memory.

2. Modifier

Static modifiers are mainly functions used in this file and are not provided externally. static functions of this type are available in any file in the Linux kernel;

Static inline void enable_noirq (void ){

................

}

The advantage of using the static modifier is that all files can define functions with the same name, and compilation errors caused by duplicate names are not considered;