C#•2y ago

Crossplatform VarArg PInvoke

What's the current correct way to declare PInvoke C library function with vararg parameters that works on at least Mac, Windows, Android and Linux? I know the actual maximum number of parameters so I don't care if I have to write multiple functions, what I'm interested in is if it will work correctly on all platforms.

DemonikOP•4/15/24, 4:43 PM

(function is from )

DemonikOP•4/15/24, 4:44 PM

my idea is to declare 2 functions for different parameter lists and wrappers around them but I'm not sure if that'll correctly follow calling conventions on all platforms

DemonikOP•4/15/24, 4:46 PM

looking through information on the interet I found keyword but I'm finding very conflicting information on if it's ok to use and if it works on other platforms

DemonikOP•4/15/24, 4:46 PM

and defining multiple functions also can't find any information on if it will work on all target platforms

jcotton42•4/15/24, 4:48 PM

@Demonik I would ask this in #allow-unsafe-blocks

DemonikOP•4/15/24, 4:49 PM

ty, I'll ask there

cap5lut•4/15/24, 7:51 PM

variadic arguments r afaik not possible at ABI level, but that was regarding c++.
in #allow-unsafe-blocks this question (again for c++) comes up quite often and the recommended way was always to write a thin wrapper c library that does the varargs stuff for u.

cap5lut•4/15/24, 7:53 PM

oh sorry, just looked at the timestamps and noticed im late to the party

DemonikOP•4/15/24, 9:02 PM

I just added 1 and 2 arg variants to libopus and rebuilt it

DemonikOP•4/15/24, 9:02 PM

I'll just have to do it for all platforms

DemonikOP•4/15/24, 9:03 PM

the library itself is pure C

DemonikOP•4/15/24, 9:07 PM

the worst part is there doesn't seem to be any reason why it's exposed like that in public api, all it is is a function that receives request id and 1 or 2 arguments based on request, so it could've been just a bunch of 1 / 2 argment functions, yes it would've increased amount of functions exposed because there are like 7 of these functions and a lot of them share same requests, but still is shitty api design

cap5lut•4/15/24, 9:17 PM

i dunno much about C, i would guess maybe they couldnt come up with good names for the different functions, but looking at C function names generally ... u know xD

DemonikOP•4/15/24, 9:43 PM

I mean if you look at docs they literally have names for the functions as s which are passed to the vararg as 2nd argument

cap5lut•4/15/24, 9:45 PM

arent those macros?

DemonikOP•4/15/24, 11:02 PM

yes but they were used as constants

DemonikOP•4/15/24, 11:03 PM

example of a function

DemonikOP•4/15/24, 11:04 PM

this is example of defines

DemonikOP•4/15/24, 11:04 PM

you're supposed to call it like

DemonikOP•4/15/24, 11:05 PM

and it wlll call it like

DemonikOP•4/15/24, 11:06 PM

there is no reason I see why it couldn't have been

DemonikOP•4/15/24, 11:06 PM

it's a shitty api design that clearly ignores that languages other than C exist

DemonikOP•4/15/24, 11:08 PM

this is just one function that does a lot of things depending on 2nd argument

DemonikOP•4/15/24, 11:09 PM

this doesn't really translate to any language other than C and only works in C because of typechecking hacks used in macros