Malloc和Struct

Question

i am facing some difficulties with malloc and structs. I want to read the m_data.number_chars as shown in my code (which is an integer) to be the memory that i want to allocate.. But when i compile my code, and run it, it crushes.. Any ideas..? Thanks in advance!

#include <stdio.h>

struct movies {
int number_chars;
char name;
int made_year;
float money;
};
struct movies m_data;


int main()
{
   scanf("%d",&m_data.number_chars);
   m_data.name=malloc(m_data.number_chars);
   gets(m_data.name);
   printf("%s",m_data.name);
}

Answer 1

When calling scanf , you need to pass the address of the variable to hold the result (using the ampersand & ). This would definitely cause serious memory problems right there.

Also, name is of type char . char is not a pointer. Therefore, you cannot assign the result of malloc() to name .

You need a pointer type.

Also, "crushes" is not a technical description of what is going wrong. You'll probably get further if you can articulate your situation better.

Answer 2

Try:

#include <stdio.h>
#include <stdlib.h>

struct movies {
int number_chars;
char *name;
int made_year;
float money;
};
struct movies m_data;


int main()
{
   scanf("%d",&m_data.number_chars);
   m_data.name=malloc(m_data.number_chars);
   gets(m_data.name);
   printf("%s",m_data.name);
   free(m_data.name)
}

Answer 3

Well you were supposed to pass char* to the scanf - more specifically address of the variable on which input will be stored. You didn't do that.

No return value check for the standard functions and ofcourse you didn't use malloc earlier.

#include <stdio.h>
#include <stdlib.h>
struct movies {
    int number_chars;
    char* name;
    int made_year;
    float money;
};
struct movies m_data;


int main(void)
{
    if( scanf("%d",&m_data.number_chars)!= 1){
        fprintf(stderr, "%s\n", "Error in input");
        exit(EXIT_FAILURE);
    }
    getchar();
    if(m_data.number_chars <= 0){
        fprintf(stderr, "%s\n", "Error in number of character count");
        exit(EXIT_FAILURE);
    }
    m_data.name = malloc(m_data.number_chars+1);
    if(!m_data.name){
        perror("Malloc error");
        exit(EXIT_FAILURE);
    }
    if(fgets(m_data.name,m_data.number_chars+1,stdin)){
        printf("[%s]\n",m_data.name);
    }
    return 0;
}