See bug 1350001 comment 5 for backstory. The upshot is that I believe Mozillabuild should be updated so that when you start the 32-bit shell, it forces use of the 32-bit rust toolchain, even on 64-bit machines. Likewise starting the 64-bit shell should force use of the 64-bit toolchain. Right now it appears to just use whatever toolchain is default (although it does try to set the *target* of the toolchain correctly). However given that rustc still produces 64-bit artifacts for build scripts in this configuration, it can cause linker errors and build failures. See bug 1350001 for more info.

I'm sympathetic to this issue, but I'm not sure there's much I can at the MozillaBuild level. Any thoughts, froydnj/rillian?

Well, we could install both builds of the compiler and have start_shell set e.g. a different path for the 32-bit build. Seems like an unnecessary extra download though. I liked Alex's suggestion of stripping the MSVC location vars when invoking cargo so rustc's autodetection can find the correct linker for the host binaries.

Note that the start-shell-msvc* batch scripts do set a MOZ_MSVCBITS env var when launching that you could maybe make use of. Of course, given that the long-term desire is to eliminate the start-shell-msvc* scripts entirely, you should probably come up with a way of detecting things outside of env vars that happen to be set.

(In reply to Ralph Giles (:rillian) | needinfo me from comment #2) >I liked Alex's suggestion of stripping the MSVC location > vars when invoking cargo so rustc's autodetection can find the correct > linker for the host binaries. This is bug 1350001 comment 9, for reference. This seems like the cleanest way to do things to me, too.

Ok, I guess we can close this bug and do the work of stripping the vcvars stuff in bug 1350001.