Pointer to a two-dimensional array

Recently, I used my mobile phone to learn C Language , I found a problem . Described below .

/*  Whether the main test procedures can pass  */
int main()
{
    
char test[5][5];
move(test);
}

void move(char** ptest)
{
    
    ;
}

Compiled with mobile phone software , The following information was obtained , It needs careful analysis .

A wrong passage
Compile error: …/Main.c: In function ‘main’:
…/Main.c:66:9: warning: passing argument 1 of ‘move’ from incompatible pointer type [-Wincompatible-pointer-types]
move(test);
^~~~
Wrong second paragraph
…/Main.c:27:19: note: expected ‘char **’ but argument is of type 'char (*)[5]
’
void move(char ** p)
~~~~~~~^

The first paragraph of the error explains the prerequisites for compilation errors ：
gcc Compiler added
[-Wincompatible-pointer-types]
after ,
The compiler warns ： Inconsistent pointer conversion

The second paragraph of the error tells the cause of the compilation error ：

1. Expectant (expected) Input type ：char**
2. move The entry parameter of is char (*)[5]

Pass in move The input parameters of the function char test[5][5], and move The type that the function accepts is Array pointer （ Short for pointer to a two-dimensional array ）：char (*)[5]
Here are a few questions that need to be clear ：

• At this point, the compiler , Think char test[5][5] Of “ Simplified type ” yes char (*)[5]
• Why does the compiler think that char ()[5], instead of char ()[6]、char (*)[7] Wait a minute ？ Because the compiler based on the existing input parameters char test[5][5] Inferential .
  So the correct way to write the above code is ：

/*  Whether the main test procedures can pass  */
int main()
{
    
char test[5][5];
move(test);
}

void move(char (*ptest)[5])
{
    
    ;
}

Why? char test[5][5] Of “ Simplified type ” Not what the compiler thinks is wrong char** type , It is char (*)[5] type ？
Because this representation is a static representation of two-dimensional arrays . It can also be called row pointer notation . It can be defined as follows ：

include<string.h>
#include<stdio.h>
char y[3][5];
typedef char (*line)[5] ;
int main(int argc, char *argv[])
{
    
	line x=y;
	strcpy(x[1],"54");
	printf("%s",x[1]);
}

char** Can dynamically define a two-dimensional array . It can be defined as ：

#include<stdio.h>
void test(char** p);
int main(int argc, char *argv[])
{
    
	char **p = new char*[3];
    for(int i = 0;i < 3;i++)
    {
    
        p[i] = new char[5];
    }
    test(p);
}
void test(char** p)
{
    
	    //test
    p[0][2]=100;
    p[0][1]=48;
    p[2][4]=255;
    for(int i=0;i<3;i++)
    for(int j=0;j<5;j++)
    {
    
       printf("p[%d][%d]=%c\n",i,j,p[i][j]);
    }
}