C program crashes

Question

Hi I need some help with debugging my program: It should read from the Console, process the input and give it back out:

The error occures after while(scanf("%15s", input) != EOF) is called the 2nd time. Unfortunately I can't tell you what the error is, because the progam freezes and doesn't give me any Information. I think there is something wrong with the input var (it is passed multiple times)

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

char* repeat(char c, int n);
char* drawLabel(char* label, int n);
char* drawBarnorm(char* label, int value);
char* drawBar(char* label, double value);

int main(void)
{
    char* input;
    double numIn;
    char buf[] = "";
    char* pOutput = &buf[0];

    while(scanf("%15s", input) != EOF)
    {
        scanf("%lf", &numIn);
        if (numIn > 1)
        {
            if (numIn > 30)
            {
                printf("num to big!\n");
                return 0;
            }

            strcat(pOutput, drawBarnorm(input, (int)numIn));
        } else
            {strcat(pOutput, drawBar(input, numIn));}


        printf("%s\n", pOutput);
    }

    printf("%s\n", pOutput);
    return 0;
}

char* repeat(char c, int n)
{
    char* out = (char*)malloc(sizeof(char)*50);
    int i, len;
    out[0] = '\0';

    for (i = 0; i < n; ++i)
    {
        len = strlen(out);
        out[len] = c;
        out[len+1] = '\0';
    }

    return out;
}

char* drawLabel(char* label, int n)
{
    if (strlen(label) > n)
    {
        char* newLabel = (char*)malloc(sizeof(char)*(n+1));
        newLabel[0] = '\0';
        strncpy(newLabel, label, n);
        newLabel[n] = '\0';
        return newLabel;
    } else if (strlen(label) < n)
    {
        strcat(label, repeat(' ', n-strlen(label)));
    }

    return label;
}

char* drawBarnorm(char* label, int value)
{
    char* bar = (char*)malloc(sizeof(char)*41);
    char* barPart;
    bar[0] = '\0';
    bar = drawLabel(label, 8);
    strcat(bar, "|");
    barPart = drawLabel(repeat('#', value), 30);
    strcat(bar, barPart);
    strcat(bar, "|");
    return bar;
}

char* drawBar(char* label, double value)
{
    int val = (int)(30.0*value);
    return drawBarnorm(label, val);
}

Thank you for helping me out with this.

Answer 1

char* input = malloc(size); /* Allocate memory of your wish */

Allocate memory to input You have not initialized your pointer.

The pointer should be pointing to some valid memory location to store the value through scanf()

Answer 2

You have to initialize input or declare it as an array like this

char input[16];

also, you should notice that scanf does not return EOF it returns the number of arguments matched, so you have to change

while(scanf("%15s", input) != EOF)

to

while(scanf("%15s", input) == 1)

because while(scanf("%15s", input) != EOF is always true.