c - Keeping the value of a String initialized into a function -

i know title isn't clear, clearer code + examples. want initialize char* ("motsecret" in main, "mot" in function) containing word selected randomly file, doing function. array made dynamic using memory allocation. variable in function initialized, when print value after exited function, value change , become "0@"

here part concerned in main :

int main() {     file* dico =null;     char *motsecret, *motres;     char lettre=' ';     int check=0, nbcoups=10, longueur=0, nbmots=0;     bool erreur = true;      srand(time(null));     nbmots = scandico(dico);     getword(dico, nbmots, motsecret);     printf("mot : %s", motsecret); 

the problem appears after function getword(). here code of function :

void getword(file* dico, int nblignes, char *mot) {     int nummotchoisi=rand() % nblignes, nbchar=0;     char charactuel=' ';      dico = fopen("dico.txt", "r");     rewind(dico);     if(dico != null)     {         while (nummotchoisi > 0)         {             charactuel = fgetc(dico);             if (charactuel == '\n')                 nummotchoisi--;         }         charactuel = ' ';         while(charactuel != '\n')         {             charactuel = fgetc(dico);             nbchar++;         }         fseek(dico,-(nbchar)-1,seek_cur);         mot = malloc(nbchar * sizeof(char));         if(mot == null)         {             printf("probleme d'allocation memoire");             exit(0);         }         fgets(mot, size, dico);         mot[strlen(mot) - 1] = '\0';         printf("mot = %s ", mot);     }      fclose(dico); } 

the printf @ end of function return value, , printf after getword() in main show value changed in function haven't been "saved"...

other thing, works fine without memory allocation.

i hope i'm clear enough. if forgot tell or if need more informations, please tell me.

c uses pass value in function parameter passing.

you need double pointer, void getword(file* dico, int nblignes, char **mot) if want allocate memory inside function.

as cascased effect, printf("mot : %s", motsecret); trying access uninitialized memory, causing undefined behaviour.

suggestions:

1. i see no reason use file *dico parameter in getword(). in can local.

2. instead of using double pointer, recommend returning allocated pointer getword(), i.e., change void getword() char * getword(), add return mot , use motsecret = getword(<params>)