指针在C中失去价值

Question

I have a struct which has a char * to act as it's name for finding it. I also have an array of struct declared. I am trying to assign a struct a name, but the problem I am having is the char * is continuing to change values to whatever the last name is set. This is wrecking havoc for the logic of my code. I have tried using malloc() , but that did not change the results.

code:

struct foo {
       char* label;
}
typedef struct foo fum;
fum foolist[25];
/*initialize all elements in foo list to be "empty"*/
bool setArray(char* X) {
      for(int i =0; i <25;i++) {
           if(strncmp("empty", foolist[i].label,5*sizeof(char))==0) {
                    //tried char* temp = (char*)malloc(32*sizeof(char));
                    //foolist[i].label = temp; no change.
                    foolist[i].label = X;
                    return true;
           }
      }
      return false;
}

I want label to not change with 'X' once the declaration is made, i have tried using malloc() , probably not correctly though.

Answer 1

You can do either:

foolist[i].label = malloc(strlen(X) + 1);
if ( !foolist[i].label ) {
    perror("couldn't allocate memory"):
    exit(EXIT_FAILURE);
}
strcpy(foolist[i].label, X);

or, if you have strdup() available:

foolist[i].label = strdup(X);
if ( !foolist[i].label ) {
    perror("couldn't allocate memory"):
    exit(EXIT_FAILURE);
}