C- Dynamic memory allocation for an array of strings problem-CodePudding

I'm working on a project and I need to dynamically allocate an array of strings. Each string is a line from a csv file. The problem is that on the final array, every string of the array but the last one is gibberish. I'm still learning pointers and I can't figure out what's happening.

CSV File:

ZeManel,10032003,7,B,12,50
AntonioSilva,03102002,8,A,23,15
AlbinoFerreira,25122001,9,C,2,31
AntonioSilva,14112000,12,E,1,89.4

Code:

void sorting(){

FILE *fp = fopen("C://Users//G512L//CLionProjects//ProjetoPPP//active_students.csv", "r"), *fp_temp = ("C://Users//G512L//CLionProjects//ProjetoPPP//active_students.csv", "w");
char str[MAXCHAR], **strings, buffer[MAXCHAR];
int lines_count = 0, ctrl = 0, length = 0;



if(fp == NULL) {error_op_fl();}
else{

    while(fgets(str, MAXCHAR, fp) != NULL){
        lines_count  ;
    }
    rewind(fp);

    while(fgets(buffer, MAXCHAR, fp) != NULL) {
        strings = malloc(lines_count * sizeof(char *));
        length = strlen(buffer);
        buffer[length] = '\0';
        strings[ctrl] = malloc(length * sizeof(char));
        strcpy(strings[ctrl], buffer);
        ctrl  ;
    }

    for(int x = 0; x < lines_count; x  ){
        printf("%s\n", strings[x]);
    }

}
free(strings);

Output:

 P☺3┌↓☻
░x3┌↓☻
(null)
AntonioSilva,14112000,12,E,1,89.4

The last line of the output is the only one correct

CodePudding user response：

You are reallocating your outer array on every line

while(fgets(buffer, MAXCHAR, fp) != NULL) {
    strings = malloc(lines_count * sizeof(char *)); <<<<=====
    length = strlen(buffer);
    buffer[length] = '\0';
    strings[ctrl] = malloc(length * sizeof(char));
    strcpy(strings[ctrl], buffer);
    ctrl  ;
}

That should be done only once, plus you need 1 for the string

strings = malloc(lines_count * sizeof(char *));

while(fgets(buffer, MAXCHAR, fp) != NULL) {
    length = strlen(buffer);
    //buffer[length] = '\0'; <<< === not useful since strlen tells you the location of terminating null
    strings[ctrl] = malloc((length   1) * sizeof(char)); <<<===  1
    strcpy(strings[ctrl], buffer);
    ctrl  ;
}