As far as I can tell, D's DMD can cross compile but not link. I probably missed that before (actually, I think I was trying with LDC, I found the page where they document the process while searching for it just now: https://wiki.dlang.org/Cross-compiling_with_LDC if you try those options, nothing works, at least from MacOS).
I just tried and this only works with the -c option (compile, but not link):
dmd -os=linux -c source/app.d
``` Error: linker exited with status 1 cc app.o -o app -m64 -Xlinker -no_compact_unwind -L/Users/me/dlang/dmd-2.109.1/osx/bin/../lib -Xlinker -Bstatic -lphobos2 -Xlinker -Bdynamic -lpthread -lm (dmd-2.109.1) ```
I am sure Walter knows how to compile on one machine, then go to another machine and do the linking or whatever is needed. I know nothing about those, but with Zig I need not know anything other than which flag to use to cross compile. It's a huge difference. D should do that, otherwise it's just not competitive for people like me (I am just an average joe programmer who knows how to write code but has very little interest in learning how linkers work).
Historically, you would or at least could get your compiler and linker from different vendors -- assembler, disassembler and other tools too. So it's normal/common for C compilers like gcc, clang, dmd to not be distributed like Zig is.
But I would dare say that the way Zig is doing it is a great model for others.
> go to another machine and do the linking
BTW - if you use something like debian/ubuntu for development, they have compilers+linkers+binutils for several different architectures available to make cross-building without Zig at least a little bit easier.
It would be awesome to have a post explaining how to do that :)
I've had a look and saw that Zig is still implementing the `ld` command, but there's already a `ld.ldd` command which might work if you know what magical options to use. I've tried to link my D object file but it can't find a whole lot of generated symbols, and a quick search online does not tell me where do I get those symbols from. That's always what happens when I try to do stuff with D that's not well documented.
I tried this (used the dmd -v option to get the linker command):
zig ld.lld -L/Users/me/dlang/dmd-2.109.1/osx/bin/../lib app.o
```
ld.lld: error: undefined symbol: _d_assert_msg >>> referenced by myd/source/app.d >>> app.o:(_D4core8internal5newaa__T6makeAATAyaTiZQoFNaNeHQoiZSQByQBwQBq7AAShell) >>> referenced by myd/source/app.d >>> app.o:(_D3std6format5write__T14formattedWriteTSQBm5stdio4File17LockingTextWriterTaTS3app__T9StringMapTiZQnZQDaFNfKQCqMxAaQBmZk) >>> referenced by myd/source/app.d >>> app.o:(_D3std6format5write__T14formattedWriteTSQBm5stdio4File17LockingTextWriterTaTS3app__T9StringMapTiZQnZQDaFNfKQCqMxAaQBmZk) >>> referenced 27 more times
ld.lld: error: undefined symbol: _aaLen >>> referenced by myd/source/app.d >>> app.o:(_D4core8internal5newaa__T6makeAATAyaTiZQoFNaNeHQoiZSQByQBwQBq7AAShell) >>> referenced by myd/source/app.d >>> app.o:(_D3std6format8internal5write__T15formatValueImplTSQBw5stdio4File17LockingTextWriterTHiHAyaiTaZQClFNfKQCaQuMKxSQEeQEd4spec__T10FormatSpecTaZQpZv) >>> referenced by myd/source/app.d >>> app.o:(_D3std6format8internal5write__T15formatValueImplTSQBw5stdio4File17LockingTextWriterTHAyaiTaZQCjFNfKQByQsMKxSQEcQEb4spec__T10FormatSpecTaZQpZv)
ld.lld: error: too many errors emitted, stopping now (use --error-limit=0 to see all errors)
```
Do you know how to get past that?