ANSI C - struct **变量是什么意思？

Question

In ANSI C, what does struct **variable mean? For example:

typedef struct estructuraPersona{
  char nombre[30];
  char apellido[30];
} tyPersona;

typedef tyPersona *ptrTyPersona;

ptrTyPersona functionFive(ptrTyPersona *ptrPtrTyPersona) {
  ptrTyPersona *pptP= (ptrTyPersona *)malloc(sizeof(tyPersona));
  if (*pptP == NULL) {
    printf("Error al crear nuevo nodo!");
    return NULL;
  }
  return pptP;
}

I get an error when compiling the code.

Answer 1

Do

ptrTyPersona* functionFive(ptrTyPersona *ptrPtrTyPersona){

instead of

ptrTyPersona functionFive(ptrTyPersona *ptrPtrTyPersona){

Answer 2

This function

ptrTyPersona functionFive(ptrTyPersona *ptrPtrTyPersona){
  ptrTyPersona *pptP= (ptrTyPersona *)malloc(sizeof(tyPersona));
  if(*pptP == NULL){
    printf("Error al crear nuevo nodo!");
    return NULL;
  }
  return pptP;
}

makes no sense because parameter ptrPtrTyPersona is not used.

I can suspect that the function should do the following

ptrTyPersona functionFive(ptrTyPersona *ptrPtrTyPersona){
  *ptrPtrTyPersona = ( ptrTyPersona )malloc(sizeof(tyPersona));

  if(*ptrPtrTyPersona == NULL){
    printf("Error al crear nuevo nodo!");
  }

  return *ptrPtrTyPersona;
}

As for the original function then function return type is ptrTyPersona but the function returns pointer pptP of type ptrTyPersona *

And in this statement

  ptrTyPersona *pptP= (ptrTyPersona *)malloc(sizeof(tyPersona));

there is allocated structure tyPersona so you should use pointer of type ptrTyPersona to refer the allocated memory but you use pointer of type ptrTyPersona *