example_pointer_array.c

#include <stdio.h>
#include <stdlib.h>

/*
https://www.infoq.com/news/2020/08/c2rust-transpiler
C type systems hide so much relevant information required to make even basic assumptions.
For example, if we take strncpy declaration, it really requires its two arguments destination and source to be arrays,
but its signature hides this fact behind the generic notion of a pointer to a character:

char* strncpy (char* destination, const char* source, size_t num);


Even though some languages are context-sensitive, context-sensitive grammars are rarely used for describing computer languages.
For instance, C is slightly context-sensitive because of the way it handles identifiers and type,
but this context-sensitivity is resolved by a special convention, rather than by introducing context-sensitivity into the grammar.
http://matt.might.net/articles/grammars-bnf-ebnf
*/

//characters
void functionxyz_char(char**     outVariable)
{
    *outVariable = malloc( 2 * sizeof(char) );
    (*outVariable)[0] = 'A';
    (*outVariable)[1] = 'B';
    printf("Inside functionxyz_char \n");
    printf("theVariablechar[0] = %c \n",(*outVariable)[0]);
    printf("theVariablechar[1] = %c \n",(*outVariable)[1]);
    printf("Address[0] = %p \n", &( (*outVariable)[0] )   );
    printf("Address[1] = %p \n", &( (*outVariable)[1] )   );
}

//strings
void functionxyz_string(char***     outVariable)
{
    *outVariable = malloc( 2 * sizeof(char*) );
    (*outVariable)[0] = "A";
    (*outVariable)[1] = "B";
    printf("Inside functionxyz_string \n");
    printf("theVariablestring[0] = %s \n",(*outVariable)[0]);
    printf("theVariablestring[1] = %s \n",(*outVariable)[1]);
    printf("Address[0] = %p \n", &((*outVariable)[0]));
    printf("Address[1] = %p \n", &((*outVariable)[1]));
}

int main() {
    /*
    foo[x]     = *(foo + x)
    *(foo[x])  = *( *(foo + x) )
    (*foo)[x]  = *(  *foo + x  )
    
    if you do *outVariable[0] it works necause *outVariable[0] is basically **outVariable
    So &theVariable[1] is & (theVariable[1])  and not (&theVariable)[1]
    
    variable char    = character value									=> char x = 'A';
    variable char*   = character pointer / character array              => char *x = { 'A', 'B', 'C', 0 };
    function argument char**  = reference value to character array
    
    variable char*   = string                                           => char *y = "ABC";
    variable char**  = string pointer / string array					=> char **y = {"ABC", "DEF", "GHI", 123};
    function argument char*** = reference value to string array

    char**  reference to character array
    char*** reference to string array
    
    The last digit is number of items
    const char *a[2];
	a[0] = "blah";
	a[1] = "hmm";
	
	Here the last digit become number of character for each item
	char a[2][14];
	strcpy(a[0], "blah");
	strcpy(a[1], "hmm");

    */
    
    char*   theVariablechar       = NULL;
    functionxyz_char(&theVariablechar);
   
    printf("after function return, Address[0] = %p \n", &theVariablechar[0]);
    printf("after function return, Address[1] = %p \n", &theVariablechar[1]);
    printf("theVariablechar[0] = %c \n",theVariablechar[0]);
    printf("theVariablechar[1] = %c \n",theVariablechar[1]);
    printf("\n --------- \n\n");
    
    char**   theVariablestring    = NULL;
    functionxyz_string(&theVariablestring);
    
    printf("after function return, Address[0] = %p \n", &theVariablestring[0]);
    printf("after function return, Address[1] = %p \n", &theVariablestring[1]);
    printf("theVariablestring[0] = %s \n",theVariablestring[0]);
    printf("theVariablestring[1] = %s \n",theVariablestring[1]);
    
    return 0;
}
/*
Inside functionxyz_char 
theVariablechar[0] = A 
theVariablechar[1] = B 
Address[0] = 0x5634e70382a0 
Address[1] = 0x5634e70382a1 
after function return, Address[0] = 0x5634e70382a0 
after function return, Address[1] = 0x5634e70382a1 
theVariablechar[0] = A 
theVariablechar[1] = B 

 --------- 

Inside functionxyz_string 
theVariablestring[0] = A 
theVariablestring[1] = B 
Address[0] = 0x5634e70386d0 
Address[1] = 0x5634e70386d8 
after function return, Address[0] = 0x5634e70386d0 
after function return, Address[1] = 0x5634e70386d8 
theVariablestring[0] = A 
theVariablestring[1] = B
*/