Re: [cc65] Code generation of "jsr enter"

On Mon, Mar 12, 2007 at 05:29:50AM -0800, Mike Harris wrote:
> I'm using cc65 to compile some simple C code, and I'm a bit confused as to
> some of the assembly it's generating.
>
> I see "jsr enter", "jsr pusha", and "jsr leavey" in the generated assembly,
> but I don't see them defined anywhere. This assembles fine though, so I'm not
> sure whats going on or what those subs do.
>
> Can someone shed some light on this?

These functions are part of the runtime library. They're linked in by the -
you guessed it - linker. There are hundreds of these functions and most of
them are really short. If you're interested in the details, you may want to
download the source archive and have a look into the libsrc/runtime/
directory.

Hint: If your routines call "enter" and "leavey", they're probably declared
with an empty parameter list like this:

        void foo ()
        {
        }

An empty parameter list means "this function accepts any number of
parameters". The compiler inserts special code to make this possible. If what
you really want is a function that accepts *no* parameters, using

        void foo (void)
        {
        }

generates better code.

Regards


        Uz


-- 
Ullrich von Bassewitz                                  uz@musoftware.de
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