Re: LuaJIT linker error on iOS

[Mike Pall <mikelu-1202@...>]

Scott Shumaker wrote:
> I'm including luajit in my iOS project (as a static library), and I
> get the following linker errors:
>
> Undefined symbols for architecture armv6:
>  "___aeabi_cdcmple", referenced from:
>
> [...]
>
> BTW, this is using iOS5.0.

Well, yes, this is a known problem. Some other users have written
to me with the same issue. The iOS build of LuaJIT is broken for
the latest XCode 4.2 (i.e. iOS 5.0). Or rather the Clang/LLVM
version, that comes with it, is broken.

Those symbols are a mandatory part of the ARM EABI. They are
needed by LuaJIT/ARM, because this is (still) a soft-float-only
port. It uses soft-float function calls, even if you're compiling
for a CPU which has a hardware FPU (VFP).

<rant> Apparently, some clever soul at Apple decided to strip
those functions from Clang (and violate the ARM EABI). But hey,
it's Apple and they define their own standards, anyway. And they
truly love to break plenty of interesting stuff on every release.
Building cross-platform apps that work on Apple's "lifestyle gear"
("hardware" sounds way too durable in comparison) is a nightmare
and I'm lead to believe this is fully intentional. </rant>

Oh well, I don't have an easy solution for this. I've been working
on this problem with someone, who helped me with the iOS port. We
guessed those soft-float functions might still be present somewhere
in the default libraries, except under different names (__divdf3
etc.). But we didn't get around to figure out the details, yet.

> I appeared to have fixed it, I had to link against libgcc, which you
> can find here:
>
> /Developer/Platforms/iPhoneOS.platform/Developer/usr/llvm-gcc-4.2/lib/gcc/arm-apple-darwin10/4.2.1
>
> There's a couple different variants, depending on whether you're
> building for armv6 or armv7.

Good to hear this fixes your problem! Alas, this is not a general
solution, of course. I don't see an easy way to deduce the required
library path and file name. Hardcoding these is certainly going to
break on the next release of XCode and/or on previous releases.

--Mike