Malloc Problem

Peterwkc

Why this program have run time error ?

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// Malloc.c  -- String version
 
#include<stdio.h>

#include<stdlib.h>
 
int main(int argc, char * argv[])

{

    int number, loop;

    char *string;
 
    printf("How many number of characters : ");

    scanf("%d", &number);
 
    string = malloc (number);
 
    for (loop=0;loop<number;loop++)

    {

        scanf("%c", &string[loop]);

    }
 
    for (loop=0;loop<number;loop++)

    {

        printf("The string is %s", *(string + loop));

    }
 
    return 0;
 
}
 
// Why this program got run time error ? 

// Please correct my mistake and i can learn from mistake

Thanks for oyur help.

Your help is greatly appreciated by me and others.

Banfa

There are 2 errors.

1. You have not zero terminated your string. In C/C++ the end of character arrays used as strings are indicated by the 0 character '\0'. You have not put one in your variable string and you have not allocated memory for it (you need a + 1). An array of characters holding a string must always be at least 1 longer than the string itself to hold this 0 terminator.

2. In the code line

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printf("The string is %s", *(string + loop));

%s indicates a string, a variable of type char * but you pass it a variable of type char. Additionally by using (string + number) you actually reference the position where the 0 terminator for the string should be (but isn't).

Peterwkc

I couldn't understand what you say in second infromation. Sorry for my stupidness.

By the way, i have changed the size to store null terminated character but still have run time error.

Below is my code:

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// Malloc.c  -- String version
 
#include<stdio.h>

#include<stdlib.h>
 
int main(int argc, char * argv[])

{

    int number, loop;

    char *string;
 
    printf("How many number of characters : ");

    scanf("%d", &number);
 
    string = malloc (sizeof(char) * (number + 1));
 
    for (loop=0;loop<number;loop++)

    {

        scanf("%c", &string[loop]);

    }
 
    *(string + number) = '\0';

    for (loop=0;loop<number;loop++)

    {

        printf("The string is %s", *(string + loop));

    }
 
    return 0;
 
}
 
// Why this program got run time error ? 

// Please correct my mistake and i can learn from mistake

Thanks for your help.

Your help is greatly appreciated by me and others.

Banfa

Quote:

Originally Posted by Peterwkc

I couldn't understand what you say in second infromation. Sorry for my stupidness.

Well why don't you try explain to me what you think

*(string + loop)

in your printf line represents.

Ganon11

Also, when you assign string to the result of your malloc() call, you don't cast the result to a (char *). malloc() returns a void *, not a char*.

Banfa

Quote:

Originally Posted by Ganon11

Also, when you assign string to the result of your malloc() call, you don't cast the result to a (char *). malloc() returns a void *, not a char*.

Strictly speaking that is not an error because this is C code not C++ code. C supplies an inctrinsic cast from void * to most other data pointer types which C++ does not because of its stricter typing. In fact in C it is an error to put in unnecessary casts like that amd to override the compilers intrisic casting rules.

chella

Hi,
I think the problem is with the scanf statement inside the first for loop.

It is not advisable to use scanf for a character. For More details please look into this website.

http://www.gidnetwork.com/b-60.html

And in the printf statement inside the second for loop should use "%c" format.

Regards,
chella

Peterwkc

Thanks for all the reply.

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