build compiler on mingw

[emekoi]

is zig tested regularly on mingw(-w64), or is it known to compile successfully there?

[andrewrk]

We used to test building for mingw in the CI, but the mingw llvm packages were outdated for too long, and I was unable to build LLVM and libclang from source with mingw. This will eventually be solved by #853

[emekoi]

i've gotten it to compile but is doesn't work in the console (exits with exit code 127) or gdb (exits with error code 0xc0000139 before main is even run); however it will open in cmd and git bash but it will segfault when i try to run the tests or compile anything.

[andrewrk]

Yeah. At this point, only builds with msvc are supported. It would be nice to add mingw support before #853 is solved, but it was too hard to test, since the packages didn't have the latest llvm version, and building llvm from source didn't work.

We're about to depend on LLVM 7.0.0 which is scheduled to be released this week. I'm guessing those packages won't be available in mingw for several months.

[ghost]

if building llvm with mingw did not work because of timeouts we could fix this with
#835 (comment) , if its because of some other issue then this would not help obviously (quick closed-issue search did not reveal anything).

[emekoi]

huzzah! the problem was that zig was loading the wrong dll (dlls from qemu) instead of the ones from mingw. now i can work on that segfault...

[emekoi]

ok this is weird but the first time i run the compiler it segfaults but after that it starts giving proper error messages, then it will repeat this every time it gets further than it did last time.

[andrewrk]

I wonder if that's trying to compute the compiler id. Try wiping ~/.local/share/zig/stage1/ and then running zig id.

[emekoi]

that worked but now i have to rebuild because of reasons.

[emekoi]

it works!!! now i just need to run the test suite....
which tests depend on linking to libc? because linking to libc isn't supported yet.

[andrewrk]

which tests depend on linking to libc?

Here's an example to test libc detection:

$ ./zig build-exe ../example/hello_world/hello_libc.zig --library c
$ ./hello
Hello, world!

[emekoi]

no i mean which don't link to libc. as zig is now it doesn't support linking to libc on mingw so i can't run these tests. or is there a way to keep the test harness running if some tests fail?

[andrewrk]

./zig test ../test/behavior.zig
./zig test ../std/index.zig

That covers most stuff without depending on libc. We could also add a flag to the main test command that would exclude libc stuff.

[emekoi]

does zig need to link to compiler-rt? or does it only link to libLLVM, libclang, and libLDD?

[andrewrk]

It only links to libLLVM and libclang.

LDD is source-embedded in zig and compiler rt is built lazily from zig source for the target.

[emekoi]

so i don't need libssp, libcxx, etc.?

[andrewrk]

I'd be happy to look at a paste of errors that you're getting if you're having trouble. Zig only depends on a c++ compiler, libclang, and libllvm.

[emekoi]

it's not that i'm getting errors building zig, it's that i;m building the llvm 7 tool chain from scratch so i can use the most recent version on zig. i was having problems with getting compiler-rt to compile so i thought it best to ask if was actually needed.

[emekoi]

currently, elf format is chosen as the default on mingw if you built llvm from source. is there a way to change the default target?
EDIT: i think i narrowed the error down to how llvm parses target triples.