How do I use C libraries in assembler?

Question

I want to know how to write a text editor in assembler. But modern operating systems require C libraries, particularly for their windowing systems. I found this page, which has helped me a lot.

But I wonder if there are details I should know. I know enough assembler to write programs that will use windows in Linux using GTK+, but I want to be able to understand what I have to send to a function for it to be a valid input, so that it will be easier to make use of all C libraries. For interfacing between C and x86 assembler, I know what can be learned from this page, and little else.

Answer 1

One of the most instructive ways to learn how to call C from assembler is to:

1. Write a C program that calls the C function of interest
2. Compile it, and look at the assembly listing (gcc -S)

This approach makes it easy to experiment by starting with something that is already known to work. You can change the C source and see how the generated code changes, and you can start with the generated code and modify it yourself.