for some reason I get a segmation fail(core dump) but only on the second run in the loop. some background ptr is declared as char* in main() and initialized as NULL. Attaching screenshot of the code and prints

char* get_command(char **str) {
    char c;
    int i,add=0;
    printf("\tget command\n");

    for(i=0; (c=getchar())!= '\n';i  ) {
        if(i==TOTAL_CHAR*add){
            *str = (char*)realloc(*str,sizeof(char)*TOTAL_CHAR*

    (  add));
    printf("\tmemory alocate succede\n");
        if (*str==NULL) {/*warning if realloc has failed*/
            fprintf(stderr,"ERROR:: realloc fail");
            exit(0);
        }
    }
    
    **(str i)=c;
    printf("\tchar should be: %c, actual: %c\n",c,**(str i));

    }
    return *str;
}

enter image description here

CodePudding user response：

**(str i)=c; it needs to be *(*str i)=c;

char* get_command(char **str)
{
    char c;
    int i,add=0;
    printf("\tget command\n");

    for(i=0; (c=getchar())!= '\n';i  )
    {
        *str = (char*)realloc(*str, i   2);
        if (*str==NULL)
        {/*warning if realloc has failed*/
            fprintf(stderr,"ERROR:: realloc fail\n");
            free(*str);
            exit(0);
        }
    
        *(*str i)=c;
        printf("\tchar should be: %c, actual: %c\n",c,*(*str i));
            
    }
    *(*str   i) = 0;   
    return *str;
}

int main(void)
{
    char *s = NULL;

    get_command(&s);
    printf("string: \"%s\"\n", s);
}

https://godbolt.org/z/T4PMTjn3s