problem: function should have a prototype

[iqbalbd]

I have a problem. function should have a proto type. any body help me..

#include<stdio.h>
#include<string.h>
  main()
{
 
 
    char arr[10];
    printf("Enter a string to reverse\n");
 
       gets(arr);
 
    streev(arr);
 
       printf("Reverse of entered string is \n%s\n",arr);
 
       return 0;
}

[Anas Mosaad]

line 12, should be strrev instead of streev.

[donbock]

This didn't cause the error message, but line 3 should be:

int main(void)

[swapnali143]

Here function to reverse string is strrev()
and u used streev() which is not defined in libraries of c

Syntax of strrev() is

strrev(string);
Correct code is as follows

    #include<stdio.h>
    #include<string.h>
      main()
    {
 
 
        char arr[10];
        printf("Enter a string to reverse\n");
 
           gets(arr);
 
        strrev(arr);
 
           printf("Reverse of entered string is \n%s\n",arr);
 
           return 0;
    }
 
 

[Anas Mosaad]

That's what I said earlier.

@donbock, not sure if your statement is correct. I remember from our C class (more than a decade from now) that we could have a main without an int return type.

[Banfa]

@Anas Mosaad quite a few C/C++ courses around the world seem to teach that main can return void. The problem is 2 fold

a. They are using an old non-standard compiler that kind of supports this return type.

b. They are wrong. The C/C++ standards* prohibits a return type from main other than int.


* Strictly speaking the C++ standard prohibits a return type from main other than int. The C standard allows a return type other than int (normally void) but this is considered a compiler extension and as such is completely non-portable.

In general it is a good idea to avoid compiler extensions if at all possible as you never know when you may need to use a different compiler and you can't be sure it will have the same extensions.

[Anas Mosaad]

I agree @Banfa with your post. However I keep my words that the statement should never give such an error as @donbock was trying to says in his post!

[donbock]

As I said, your "function should have a prototype" error message has nothing to do with your main declaration.

Refer to the C FAQ:

What is the correct declaration of main?
Can I declare main as void?
But what about main's third argument envp?
I believe that declaring void main() can't fail.
So what could go wrong?
The book I've been using always uses void main().

[Anas Mosaad]

@donbock, I'm not a native English speaker but I think your post #3 is the opposite of #8. I'm not trying to argue you but I'm trying to make sure I understand it well.
You said "This didn't cause the error message, but line 3 should be:". I believe this means that #2 didn't cause the error and the error is should be at line 3. Is this what your statement says? or I misunderstood it?

[donbock]

What I meant in post 3 was that nothing I was about to say about the proper declaration of main() had anything to do with the error message you reported in your original post.

[Anas Mosaad]

I misunderstood that statement. Anyway, thanks for the clarification :-)