如何在C中链接两个文件

Question

I am currently working on a class assignment. The assignment is to create a linked list in c. But because we it's a class assignment we have some constraints:

We have a header file that we cannot modify. We have ac file that is the linkedlist We have ac file that is just a main method just to test the linkedlist

the header file has a main method defined, so when I attempt to build the linkedlist it fails because there is no main method. What should I do to resolve the issue?? Import the test file (this causes another error)?

Answer 1

I'm assuming your three files are called header.h, main.c, and linkedlist.c

gcc main.c linkedlist.c -o executable

This will create an executable binary called "executable"

Note this also assumes you're using gcc as a compiler.

Answer 2

Like most languages, C supports modules. What I assume your assignment requires is compiling a module. Modules, unlike full programs, lack entry points. Roughly speaking, they are collections of functions, in the manner of a library. When compiling a module, no linking is made. You would compile a module like this: gcc -c linkedlist.c -> this would actually produce linkedlist.o, which is a module. Try executing this linkedlist.o (after changing its mode to executable, since it won't be so by default). The reason you fail to execute this module is, partly, because it is not in the proper format to be executed. Ones of the reasons it is not so is it lacks entry point (what we know as 'main') and linkage. Your assignment seems to provide a test 'main.c', if you wanted to use it, you would only have to link the 'main.c' (actually compiled into main.o) with linkedlist.o . To actually do that, simply type in gcc -o name_of_your_program main.c linkedlist.o . In fact, what is being done here is that your compiler first compiles main.c into a main.o module, then links the 2 modules together under the name you have given it with the -o option, but the compiler is pretty smart and needs nothing explicit about the steps he needs to take. Now if you wanted to know more about this stuff, you'd have to try and learn about how compilers do what they do. Google can help you with that more than I ever could. Good luck.