Calling convention

The calling convention specifies how exactly function call and return are implemented in assembly.

C calling conventions

ANSI C does not specify assembly level calling convention to be used by implementations nor means to control actual calling conventions.

Some compilers do however contain extensions that allow to fix a given calling convention.

GCC allows to specify calling convention explicitly as:

void f (int i) __attribute__ ((cdecl));

where cdecl is the name of the calling convention.

In IA32, cdecl is the most popular in Linux, and stdcall the most popular in Windows, but there exist many others.

To call a C function from assembly you need to:

use the correct C calling convention to which the C code compiled to.

Remember that ANSI C does not specify this.
use the correct naming convention of the libraries you want to link to.

For example, exit may be called _exit on certain compilers such as GCC elf format.

This is not specified by ANSI C, so the only portable alternative is via macros.