Compile error when compiling rustc for ios.

[SirVer]

This is d0d3707.

I am trying to follow this tutorial to learn something about iOS. It contains a step about cross compiling rustc for iOS:

$ mkdir build && cd build
$ ../configure --target=armv7-apple-ios,armv7s-apple-ios,i386-apple-ios,aarch64-apple-ios,x86_64-apple-ios --prefix=/opt/rust-ios-toolchains

$ make -j8
...tons of output...

rustc: x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/librustc_bitflags
rustc: x86_64-apple-darwin/stage2/lib/rustlib/armv7-apple-ios/lib/liballoc
rustc: x86_64-apple-darwin/stage2/lib/rustlib/armv7s-apple-ios/lib/liballoc
rustc: x86_64-apple-darwin/stage2/lib/rustlib/aarch64-apple-ios/lib/liballoc
rustc: x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-ios/lib/libcollections
rustc: x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/liballoc
rustc: x86_64-apple-darwin/stage2/lib/rustlib/armv7-apple-ios/lib/libcollections
rustc: x86_64-apple-darwin/stage2/lib/rustlib/armv7s-apple-ios/lib/libcollections
rustc: x86_64-apple-darwin/stage2/lib/rustlib/i386-apple-ios/lib/libcollections
rustc: x86_64-apple-darwin/stage2/lib/rustlib/aarch64-apple-ios/lib/libcollections
rustc: x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/libcollections
rustc: x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-ios/lib/libstd
rustc: x86_64-apple-darwin/stage2/lib/rustlib/armv7-apple-ios/lib/libstd
warning: dropping unsupported crate type `dylib` for target `x86_64-apple-ios`
warning: dropping unsupported crate type `dylib` for target `armv7-apple-ios`
rustc: x86_64-apple-darwin/stage2/lib/rustlib/armv7s-apple-ios/lib/libstd
rustc: x86_64-apple-darwin/stage2/lib/rustlib/i386-apple-ios/lib/libstd
warning: dropping unsupported crate type `dylib` for target `armv7s-apple-ios`
warning: dropping unsupported crate type `dylib` for target `i386-apple-ios`
rustc: x86_64-apple-darwin/stage2/lib/rustlib/aarch64-apple-ios/lib/libstd
warning: dropping unsupported crate type `dylib` for target `aarch64-apple-ios`
rustc: x86_64-apple-darwin/stage2/lib/rustlib/x86_64-apple-darwin/lib/libstd
../src/libstd/sys/unix/backtrace.rs:133:5: 133:17 error: use of unstable library feature 'result_fold': has not seen enough usage to justify its position in the standard library
../src/libstd/sys/unix/backtrace.rs:133     result::fold(iter, (), |_, _| ())
                                            ^~~~~~~~~~~~
../src/libstd/sys/unix/backtrace.rs:133:5: 133:17 help: add #![feature(result_fold)] to the crate attributes to enable
../src/libstd/sys/unix/backtrace.rs:133:5: 133:17 error: use of deprecated item: has not seen enough usage to justify its position in the standard library, #[deny(deprecated)] on by default
../src/libstd/sys/unix/backtrace.rs:133     result::fold(iter, (), |_, _| ())
                                            ^~~~~~~~~~~~
error: aborting due to 2 previous errors
make: *** [x86_64-apple-darwin/stage2/lib/rustlib/armv7-apple-ios/lib/stamp.std] Error 101
make: *** Waiting for unfinished jobs....
../src/libstd/sys/unix/backtrace.rs:133:5: 133:17 error: use of unstable library feature 'result_fold': has not seen enough usage to justify its position in the standard library
../src/libstd/sys/unix/backtrace.rs:133     result::fold(iter, (), |_, _| ())
                                            ^~~~~~~~~~~~
../src/libstd/sys/unix/backtrace.rs:133:5: 133:17 help: add #![feature(result_fold)] to the crate attributes to enable
../src/libstd/sys/unix/backtrace.rs:133:5: 133:17 error: use of deprecated item: has not seen enough usage to justify its position in the standard library, #[deny(deprecated)] on by default
../src/libstd/sys/unix/backtrace.rs:133     result::fold(iter, (), |_, _| ())
                                            ^~~~~~~~~~~~
error: aborting due to 2 previous errors
make: *** [x86_64-apple-darwin/stage2/lib/rustlib/armv7s-apple-ios/lib/stamp.std] Error 101

Seems like an honest bug - I wonder why I only see this with these config flags? Am I doing it wrong?

[azilber]

I've literally just went through this same guide a few hours ago, including the 'Makefile'. I've had a successful build and tested on iphone 4-6plus emulators. Not sure what your versions are, and it would be helpful if you posted that, but I'm on OSX 10.10.4 using Xcode 6.4 and Rust 1.1.0-dev.

I didn't follow the instructions completely though, because I woudn't really want to use nightlies for serious dev. Do multirust default stable instead instead of nightly (as nightly is 1.3 as of this writing). Do a make clean, re-run configure, and make again.

[SirVer]

As stated, I am using a current checkout, namely d0d3707.

I have no doubts that it works with earlier versions (the blog author could make it work obviously) - but the bug seems to be a real one in rust, so I reported it.

I do not get so far as to selecting a toolchain - already the building of the ios rustc fails. Of course this is a Mac OS X system (10.10.4).

[SirVer]

stable works, I checked with this:

$ git checkout stable
$ git submodule update --init --recursive
$ cd build && --target=armv7-apple-ios,armv7s-apple-ios,i386-apple-ios,aarch64-apple-ios,x86_64-apple-ios --prefix=/opt/rust-ios-toolchains && make install

the beta branch fails with the same error as current HEAD.

[steveklabnik]

/cc @brson , if this is an issue with beta but not stable, we need to figure out what's up

[alexcrichton]

iOS isn't an officially supported platform right now, so the build will inevitably fail from time to time. Feel free to submit a PR to fix this, however! The fix would either include:

• Removing the use of result::fold
• Adding #![cfg_attr(target_os = "ios", feature(result_fold))] to the crate attributes

[tamird]

I'll see about fixing this today or tomorrow

[SirVer]

Thanks!