new to C(java programmer) Help with Main() and more please?

Hi guys,
I'm new to C, just came over from the darkside of Java. I'm writing a List.c file that serves as a doubly linked list for a client module. Only problem is that List.c only compiles when it has a main function. I dont need this and when I remove the main function it gives me this error

Code:

---

> cc List.c
Undefined                      first referenced
 symbol                            in file
main                                /opt/SUNWspro/WS6U2/lib/crt1.o
ld: fatal: Symbol referencing errors. No output written to a.out

---

Otherwise it compiles just fine with an empty main function in place.

main is like start point of any C code.

without the main, the compiler doesn't know where to start. with the main the compiler comes to know this is the starting point.

you might call many other sub function with the main. it might be user defines or any library functions

main always return a value

Code:

---

int main()
{
  ...
  ...
  ...

  return 0;
}

---

ssharish2005

Quote:

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Originally Posted by ssharish2005

main is like start point of any C code.

without the main, the compiler doesn't know where to start. with the main the compiler comes to know this is the starting point.

you might call many other sub function with the main. it might be user defines or any library functions

main always return a value

Code:

---

int main()
{
  ...
  ...
  ...

  return 0;
}

---

ssharish2005

---

Ok, but why do I see C programs that dont have main?
I can post up code without a main() if you want.... does it require special compiling?
If you are saying all C programs need a main, I know that is incorrect.
Remember, I am looking to use List.c for a client module(which has a main) which will utilize List.c via List.h...I dont know how else to say it.

You don't need a main() to compile your code. You will need an entry point if you're compiling it to an executable program. Compilers (I have yet to see one that doesn't) will create an executable if you don't pass any specific options to it. In your case you seem to want to compile it to object code, check the manual for your compiler or 'cc --help' to see which flag that represents, usually it's '-c'.

> Ok, but why do I see C programs that dont have main
A C program needs a main
A C file (like list.c) does not.

My current work project has ~3000 files, but only one of them has main().

To make a program, you would need
cc prog.c list.c

Your prog.c might look like this

Code:

---

#include "list.h"
int main ( ) {
  List *mylist = ListNew();
  // more code
  ListDelete(mylist);
  return 0;
}

---

The 'main' is what brings everything together in a single highest level function which is your entire program.

without main you cann`t test the execution of your program , you only can compile it to detect errors(compile time errors / suntax errors) !!

Thanks a lot everyone. This makes sense now.
I hope to be good enough with C that I will be helping others here aswell...I owe it to the board and this community :)

Thanks guys! This is all starting to make a little more sense now.
The other problem I'm getting is "parse error". I searched about it and it usually means I typed something wrong or missed a semicolon somewhere. But I'm getting parse errors at the fourth line! How does that happen? The fourth line is blank and is a space. Above it is include files...aswell as my own #include "List.h". Does this mean something is wrong with List.h? And whats a good way to check if everything is ok? I'm probably spoiled because Java really holds your hand through errors and debugging.

Thanks guys! This is all starting to make a little more sense now.
The other problem I'm getting is "parse error". I searched about it and it usually means I typed something wrong or missed a semicolon somewhere. But I'm getting parse errors at the fourth line! How does that happen? The fourth line is blank and is a space. Above it is include files...aswell as my own #include "List.h". Does this mean something is wrong with List.h? And whats a good way to check if everything is ok? I'm probably spoiled because Java really holds your hand through errors and debugging.

it would make more sense when we have look at your code.

EDIT: you can actullay delete your double post. Click on edit button which is would displayed on to your right bottm of your post and click delete

ssharish2005