Thread: Need help with pointer problem

I am studying C my self and trying to do some exercise.
The exercise requires 2 functions, one to takes three parameters (one string holds questions, one string holds user 's answers, and one integer limits the characters of the answer. The other function is the main function that uses the previous function to ask the user and prints the full name.
I also tried to write the code but there is a problem which I can not find it out by myself. Can any one show me the mistake and explain it for me ?
Thanks all.

Code:

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

#define SIZE 100

void func(char, char, int);

int main(void)
{
    char str1[] = "Enter your first name: ";
    char str2[] = "Enter your middle name: ";
    char str3[] = "Enter your last name: ";
    char answer[SIZE];
    
    func(str1, answer, SIZE);
    
    func(str2, answer, SIZE);
    
    func(str3, answer, SIZE);
    
    printf("Your full name is: %s", answer);
}

void func(char *a, char *b, int max_size)
{
    char temp[100];
    int i;
    
    printf("%s", a);
    gets(temp);

    i = strlen(temp);
            
    if(i < max_size)
    {
        strcat(b, temp);
    }
    else
    {
        printf("You enter too much characters.");
    }
}

Originally Posted by suyaku92

But if I empty the string answer, how can I join the three parts of the name?

When I tried to run the solution, it appeared like this:

Code:

Enter your first name: suyaku // I entered suyaku
Enter your middle name: kudo // I entered kudo
Enter your last name: suyakukudo // I did not entered anything but this "suyakukudo" appeared, and if I press "Enter" button, an error box appeared... "stack arround str2 is corrupted"

Use strcat. Just make sure you put a space between the names.

Originally Posted by Salem

Post your latest code.

The code I posted first time is the lastest !

Originally Posted by Salem

> The code I posted first time is the lastest !
But I gave you two things to fix, and it still looks the same.

So either you've done nothing, except to complain that it still doesn't work. If this is what you're saying, then you're just wasting everyone's time.

Or you've made some changes, and it still doesn't work.

first, the result I posted after run the solution is NOT CHANGED after I changed gets to scanf (follow your 1st instruction)
second, i do not know how to follow 2nd instruction so i asked you again but i haven't got the answer yet

Originally Posted by MK27

So let's see it. But first...





QuantumPete answered this in post #4, but either you did not read it, or you did not understand.

This:

Code:

char answer[SIZE];

could contain any kind of garbage, because it has not been initialized. "Initialize it first" and "making sure it is empty" means something like this:

Code:

char answer[SIZE] = { 0 };

This will zero out the array. That's important, because string functions look for the first zero to, eg, concatenate onto.

Thanks all, it works.
I did not understand ( I told you I just study C myself and I did not encounter this problem before).
Sorry for your time.
Problem solved.

Everyone seems to have failed to spot the following mistake:

the function is declared as follows:

Code:

void func(char, char, int);

but then it is defined like so:

Code:

void func(char *a, char *b, int max_size)

this should be throwing compiler errors (or at least warnings) related to incorrect parameter types. perhaps you need to turn up the warning level on your compiler.