# Supporting a new target **URL:** \ **Category:** compiler\ **Created:** [December 21, 2016, 8:58pm UTC](https://internals.rust-lang.org/t/supporting-a-new-target/4483 "2016-12-21T20:58:49Z")\ **Posts on this page:** 7\ **Page:** 1
**Author:** ![wildstyle](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/wildstyle/32/6195_2.png) [@wildstyle](https://internals.rust-lang.org/u/wildstyle)\ **Post date:** [December 21, 2016, 8:58pm UTC](https://internals.rust-lang.org/t/supporting-a-new-target/4483/1 "2016-12-21T20:58:49Z")
I’m writing support for a new target in `rustc`. So far I can make staticlibs work correctly, and inline assembly, so that’s great IMO. Here’s my current challenges, I’d love to hear your thoughts: 1. Rustbuild fails for me. It’s trying to use the stage0 compiler to build my stage1 libstd. This looks like it is wrong for only my use case: bootstrapping stage1 for which no stage0-supporting-my-target exists yet. Can anyone confirm this, or am I misusing/misconfiguring rustbuild? 2. If I ignore that failure and just use my new stage1 `rustc` to try to build core by hand, I get a failure during `LLVMRustWriteOutputFile()` on one particular compile. It’s an assertion in my target, so I’m pretty sure I can take it from here. But it might be easier to investigate if I could dump the input to a file. It still encounters the assertion when I use -C emit=llvm-ir. I guess there’s no way to dump anything higher-level than that right? ---
**Author:** ![vadimcn](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/vadimcn/32/2789_2.png) [@vadimcn](https://internals.rust-lang.org/u/vadimcn)\ **Post date:** [December 21, 2016, 9:16pm UTC](https://internals.rust-lang.org/t/supporting-a-new-target/4483/2 "2016-12-21T21:16:35Z")
> [@wildstyle](#): > > Rustbuild fails for me. It's trying to use the stage0 compiler to build my stage1 libstd. This looks like it is wrong for only my use case: bootstrapping stage1 for which no stage0-supporting-my-target exists yet. Can anyone confirm this, or am I misusing/misconfiguring rustbuild? How did you configure rustbuild? I think you want something like this in your config.toml: ```rust [build] target = ["", ""] ``` i.e. you are building a compiler that still runs on the host platform, but can also cross-compile to your target. ---
**Author:** ![wildstyle](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/wildstyle/32/6195_2.png) [@wildstyle](https://internals.rust-lang.org/u/wildstyle)\ **Post date:** [December 21, 2016, 9:18pm UTC](https://internals.rust-lang.org/t/supporting-a-new-target/4483/3 "2016-12-21T21:18:04Z")
> [@vadimcn](#): > > I think you want something like this Oh! Well, now that you point it out, that's a pretty simple mistake. Thanks! ---
**Author:** ![wildstyle](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/wildstyle/32/6195_2.png) [@wildstyle](https://internals.rust-lang.org/u/wildstyle)\ **Post date:** [December 21, 2016, 9:26pm UTC](https://internals.rust-lang.org/t/supporting-a-new-target/4483/4 "2016-12-21T21:26:13Z")
Hmm, after adding the host triple to the list of targets, it still uses `./build/bootsrap/debug/rustc` and `./build/host/stage0/bin/cargo` with my desired target to build libcore. It doesn’t give an error beyond “Could not compile core”, but I assume it’s something about the target not being supported. Should I clean everything first and then restart the build after that change? ---
**Author:** ![hanna-kruppe](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/hanna-kruppe/32/6540_2.png) [@hanna-kruppe](https://internals.rust-lang.org/u/hanna-kruppe)\ **Post date:** [December 21, 2016, 10:49pm UTC](https://internals.rust-lang.org/t/supporting-a-new-target/4483/5 "2016-12-21T22:49:26Z")
You should see if you can compile core in isolation before trying to bootstrap rustc. Create a `#![no_std]` project, add a path dependency for core in Cargo.toml (point it at src/libcore/ in your rust checkout) and pass --target foo to cargo. To do this you will need a cargo that uses your custom-built rustc. Use `rustup toolchain link` to hook your rustc up to rustup’s cargo, that’s the easiest way I know of. ---
**Author:** ![wildstyle](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/wildstyle/32/6195_2.png) [@wildstyle](https://internals.rust-lang.org/u/wildstyle)\ **Post date:** [December 23, 2016, 3:11pm UTC](https://internals.rust-lang.org/t/supporting-a-new-target/4483/6 "2016-12-23T15:11:25Z")
That was a great tip (`rustup toolchain link`), @hanna-kruppe, thanks. I didn’t know about that feature. Now I can just cd to `src/libcore` and do `cargo build`. I still see that same `isRegLoc()` assertion I was hitting in #2, but it is simpler to reproduce. I’ll crank on this one for a bit and check in if I get stuck again. Thanks, all. ---
**Author:** ![system](https://sea2.discourse-cdn.com/flex002/user_avatar/internals.rust-lang.org/system/32/14092_2.png) [@system](https://internals.rust-lang.org/u/system)\ **Post date:** [March 25, 2019, 8:27am UTC](https://internals.rust-lang.org/t/supporting-a-new-target/4483/7 "2019-03-25T08:27:30Z")
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