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Error: undefined reference to winmain@16?

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Top Forums Programming Error: undefined reference to winmain@16?
# 1  
Old 11-24-2013
Error in code using Cygwin for C++
I was trying to compile the following code in cygwin using g++:

------------------------------------------

Code:
#include <iostream>
using namespace std;

int identity(int input)
{
  int output = input;
  return output;
}

------------------------------------------

I get this error:

Code:
/usr/lib/gcc/i686-pc-cygwin/4.8.2/../../../libcygwin.a(libcmain.o): In function `main':
/usr/src/debug/cygwin-1.7.25-1/winsup/cygwin/lib/libcmain.c:39: undefined reference to `WinMain@16'
collect2: error: ld returned 1 exit status

Anyone know how I can solve this?
Last edited by DyslexicChciken; 11-24-2013 at 08:54 PM.. Reason: Add CODE tags.
# 2  
Old 11-24-2013
Yes. You are using cygwin. It compiles into what amounts to a Windows executable pretending it runs under Linux.

C requires int main() as a function in your code or it cannot link. ld is the linker.

main() will have to call your function.
# 3  
Old 11-24-2013
Quote:
Originally Posted by jim mcnamara
Yes. You are using cygwin. It compiles into what amounts to a Windows executable pretending it runs under Linux.

C requires int main() as a function in your code or it cannot link. ld is the linker.

main() will have to call your function.
I tried int main() and I still got errors. With int main(), the code looks like this:

Code:
#include <iostream>
using namespace std;


int main()

  int identity(int input) 
{
    int output = input;
    return output;
  
  
}

Now I am getting this error:

Code:
bh.cpp:9:3: error: expected initializer before ‘int’
   int identity(int input)
   ^

# 4  
Old 11-25-2013
C does not require that you dump the words 'int main' into the middle of a program for no discernible reason, no.

It requires that a function named main() must exist, so that the program can begin there.

Code:
int main() {
        int output=identify(32);
}

# 5  
Old 11-25-2013
Quote:
Originally Posted by Corona688
C does not require that you dump the words 'int main' into the middle of a program for no discernible reason, no.

It requires that a function named main() must exist, so that the program can begin there.

Code:
int main() {
        int output=identify(32);
}

I fixed it:

Code:
#include <iostream>

using namespace std;

int main()
{
  int identity(int input); 
    
    int output = input;

    return output;

}

But now I get this error:


Code:
bh.cpp: In function ‘int main()’:
bh.cpp:12:18: error: ‘input’ was not declared in this scope
     int output = input;
                  ^

This is my first programming class, sorry if I am missing something obvious. My teacher tells me to find out what this program does. At school we use different operating system and a Unix terminal. I am using Cygwin on Windows vista.
# 6  
Old 11-25-2013
Again, the compiler is not asking you to jam random things into the middle of your code when it says main doesn't exist. It's asking you to add main(), unrelated to your code, outside it.

Of course, if you want your function to be run, you should tell main() to run it, since main runs everything.

Code:
#include <iostream>

using namespace std;

// Your function
int identity(int input)
{
  int output = input;
  return output;
}

// The function which the compiler will call when the program is run
int main() {
        int output=identify(32);
}

This User Gave Thanks to Corona688 For This Post:
DyslexicChciken
# 7  
Old 11-25-2013
Quote:
Originally Posted by Corona688
Again, the compiler is not asking you to jam random things into the middle of your code when it says main doesn't exist. It's asking you to add main(), unrelated to your code, outside it.

Of course, if you want your function to be run, you should tell main() to run it, since main runs everything.

Code:
#include <iostream>

using namespace std;

// Your function
int identity(int input)
{
  int output = input;
  return output;
}

// The function which the compiler will call when the program is run
int main() {
        int output=identify(32);
}

At first I got another error, but I realized you used "identify" instead of "identity", so that's fixed. Anyway, the output is nothing when I run ./bh.exe(the filename of this code). Is this correct?
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