[Good Programming habits] simplify program logic with implicit Initialization

In Figure 1, the prototype of the three APIS is mprotector_init (), mprotector_fini (), and mprotector_section_add (). Assume that mprotector_section_add () will be called by multiple tasks to initialize data related to each task. However, before mprotector_section_add () is called, you must ensure that mprotector_init () it has been executed and can only be executed once. In addition, the figure shows that task A and Task B call mprotector_section_add () in their entry functions to perform corresponding operations. Now the question is, where should mprotector_init () be called? Obviously, it is not good to put the function in the entry of task A and Task B, which results in A completely different result after the initialization sequence or priority of the task changes. Another easy way to think of is to call mprotector_init () before creating tasks A and B, so that the problem is solved. Is there a better way?

Example. c
Int mprotector_init ();
Int mprotector_fini ();
Int mprotector_section_add (section_id_t _ id, maddr_t _ start, msize_t _ size );

Void task_entry_A (void * _ p_arg)
{
Maddr_t start;
Msize_t size;
...
Mprotector_section_add (SECTION_1, start, size );
...
}

Void task_entry_ B (void * _ p_arg)
{
Maddr_t start;
Msize_t size;
...
Mprotector_section_add (SECTION_2, start, size );
...
}

Figure 1

A better method is to use the implicit initialization method, which requires some changes to the mprotector_init () and mprotector_section_add () functions, as shown in figure 2. The change in mprotector_init () allows it to be called multiple times, but adds a static local variable to record whether it has been actually initialized. When mprotector_init () if this variable is changed to true, 0 is returned directly, indicating that the operation is successful. Otherwise, subsequent Initialization is required. Finally, call mprotector_section_add () to mprotector_init.

Example. c
Int mprotector_init ()
{
Static bool initialized = false;

If (initialized ){
Return 0;
}
...
Initialized = true;
Return 0;
}

Int mprotector_section_add (section_id_t _ id, maddr_t _ start, msize_t _ size)
{
If (0! = Mprotector_init ()){
Return-1;
}
...
}
Figure 2

With these changes, users who use the mprotector_section_add () function do not need to consider where to call the mprotector_init () function, which simplifies the program logic.

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