Problem Writing a Function

[Gleeok]

No wait, 0 means register! #$%^ dammit. :mad:

Also, DarkDragon is much more knowledgeable about the ZScript compiler than I am.

What's the best way to inspect the stack without a live stack debuger? Throw out ZConsole messages with the values of the expression accumulators?

I'm sort of in the 'how does Gleeok do this' mode...which is why I was hoping for a procedural list from you, on what the flidd you would do; or some kind of step-by-step details on how to build this kind of function in the frrst place.

Honestly, I usually half forget some of this stuff, so I just go in order of: 1) Declare constants and opcodes; update script tables; implement compiler procedure as needed; update bytecode in ffscript.cpp; and finally, implement function that gets called.


[edit]
Also, what compiler are you using that doesn't have a debugger?

[DarkDragon]

ZoriaRPG, to answer your question in your commented lines: the ZScript calling convention is more or less equivalent to C's. The caller first pushes the return address onto the stack, then all of the function's explicit argument, and finally, if the function is a member function, the "this" pointer is implicitly pushed as the last argument.

The return value of the function is by convention stored in EXP1.

The callee, then, before it can return, must pop all of the arguments (including the "this" pointer) off of the stack. That's what the lines are doing that you've commented about. The ZASM instruction uses the top 4 entries of the stack, but leaves them untouched, so ZScript pops them off, then pops off the return address and jumps to it. You could use NUL instead of EXP2 for these pops if you wanted.

The reason EXP2 is used as scratch space instead of EXP1 is simply to avoid accidentally tampering with the return value of the function.

[ZoriaRPG]

ZoriaRPG, to answer your question in your commented lines: the ZScript calling convention is more or less equivalent to C's. The caller first pushes the return address onto the stack, then all of the function's explicit argument, and finally, if the function is a member function, the "this" pointer is implicitly pushed as the last argument.

The return value of the function is by convention stored in EXP1.

The callee, then, before it can return, must pop all of the arguments (including the "this" pointer) off of the stack. That's what the lines are doing that you've commented about. The ZASM instruction uses the top 4 entries of the stack, but leaves them untouched, so ZScript pops them off, then pops off the return address and jumps to it. You could use NUL instead of EXP2 for these pops if you wanted.

The reason EXP2 is used as scratch space instead of EXP1 is simply to avoid accidentally tampering with the return value of the function.

Got it. Good stuff there; and I put it into the docs. :)