fgets "Access violation writing location 0xCCCCCCCC." error

Question

Error: Unhandled exception at 0x60092A8D (msvcr110d.dll) in C_Son60.exe: 0xC0000005: Access violation writing location 0xCCCCCCCC.

When below code executed this error code is given.(Compiles successfully) Where is my mistake?

#include <stdio.h>

int i;

int main(void){

char *names[3];

//get the names of the cities
puts("Enter names of cities");
for (i = 0; i < 3; i++)
{
    fgets( names[i], 99, stdin);
}
//print entered names
for (i = 0; i < 3; i++)
{
    printf("%s", *names[i]);
}

getch();
}

0xCCCCCCCC is what MS stores in unallocated memory ... in this case, `names[i]`. — Jim Balter, Sep 17 '13 at 12:15

score 4 · Answer 1 · answered Sep 17 '13 at 12:11

4

You need to allocate memory to which the char pointers point to before you read them in

for instance:

for (i = 0; i < 3; i++)
{
  names[i] = malloc(200);
  fgets( names[i], 99, stdin);
}

answered Sep 17 '13 at 12:11

Serve Laurijssen

9,266
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3 IntelliSense: a value of type "void *" cannot be assigned to an entity of type "char *" This error is given when I did it – Lyrk Sep 17 '13 at 12:16
use `names[i] = (char *)malloc(100 * sizeof(char));` like i show in my answer @user1939432 – No Idea For Name Sep 17 '13 at 12:25
1

if you're using standard C then it will compile, you are using a C++ compiler apparently where the cast is necessary – Serve Laurijssen Sep 17 '13 at 12:26
@ServéLaurijssen it is always better to cast, and to allocate memory based on the size needed. – No Idea For Name Sep 17 '13 at 12:32
I dont agree with the "always better to cast" argument. Read this: http://stackoverflow.com/questions/605845/do-i-cast-the-result-of-malloc/605858#605858 – Serve Laurijssen Sep 17 '13 at 13:07

No Idea For Name · Accepted Answer · 2013-09-17T12:24:24.300

2 things:

you need to allocate the strings you created- you can do it with malloc(100 * sizeof(char))
when printing you do *names[i] which means - **(names + i).

all you need is names[i]

use the code:

#include <stdio.h>

int i;

int main(void){
    char *names[3];

    //get the names of the cities
    puts("Enter names of cities");
    for (i = 0; i < 3; i++)
    {
        names[i] = (char *)malloc(100 * sizeof(char));
        fgets( names[i], 99, stdin);
    }
    //print entered names
    for (i = 0; i < 3; i++)
    {
        printf("%s", names[i]);
    }

    getch();
}

score 1 · Answer 3 · edited Sep 19 '13 at 20:12

1

You must allocate your memory before storing anything into it. When you need to allocate an array of elements, and you do not know the number of elements at compile time, you must use malloc() to allocate them.

Don't forget to free your dynamically allocated memory later in order to avoid memory leaks!

edited Sep 19 '13 at 20:12

answered Sep 17 '13 at 12:11

Natan Streppel

5,759
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If I knew that each city name would be maximum 50 characters long, can I do it without using malloc? – Lyrk Sep 17 '13 at 12:29
Then you could make it an array of lenght [50] – Natan Streppel Sep 17 '13 at 12:40

fgets "Access violation writing location 0xCCCCCCCC." error

3 Answers3