Malloc Problem

[Peterwkc]

Why this program have run time error ?

// 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

		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:

// 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]

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]

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.