configure: update required LLVM version

[cardoe]

Rust 1.7.0 and newer appears to require LLVM 3.6.0 or newer when
building against a version that's out of the tree with the --llvm-root
flag.

Signed-off-by: Doug Goldstein cardoe@cardoe.com

[rust-highfive]

Thanks for the pull request, and welcome! The Rust team is excited to review your changes, and you should hear from @alexcrichton (or someone else) soon.

If any changes to this PR are deemed necessary, please add them as extra commits. This ensures that the reviewer can see what has changed since they last reviewed the code. Due to the way GitHub handles out-of-date commits, this should also make it reasonably obvious what issues have or haven't been addressed. Large or tricky changes may require several passes of review and changes.

Please see the contribution instructions for more information.

[cardoe]

I've been working on getting a newer version of Rust into Gentoo and I'd prefer to use the LLVM we ship rather than build another LLVM. I wasn't able to get it to build with anything older than 3.6.0 which is where this suggestion comes from. I've been using Rust 1.7.0 to test with.

[alexcrichton]

Hm I don't seem to recall a commit which broke 3.5 compatibility, but maybe we did by accident? What's the build error you're seeing against 3.5?

[cardoe]

error: linking with cc failed: exit code: 1
note: "cc" "-Wl,--as-needed" "-m64" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/bin/rustc.0.o" "-o" "x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/bin/rustc" "-Wl,--gc-sections" "-pie" "-Wl,-O1" "-nodefaultlibs" "-L" "/usr/lib64" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-Wl,-Bstatic" "-Wl,-Bdynamic" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_driver-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_passes-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_borrowck-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_privacy-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_typeck-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_lint-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_resolve-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "syntax_ext-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_plugin-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_metadata-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_trans-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_platform_intrinsics-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_mir-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_data_structures-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_back-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "flate-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "getopts-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "arena-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "fmt_macros-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "graphviz-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_front-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "syntax-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "term-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rustc_llvm-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "rbml-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "serialize-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "log-6a154fe0" "-L" "/var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "std-6a154fe0" "-l" "z" "-l" "pthread" "-l" "ffi" "-l" "curses" "-l" "dl" "-l" "m" "-l" "stdc++" "-l" "dl" "-l" "pthread" "-l" "gcc_s" "-l" "c" "-l" "m" "-l" "rt" "-Wl,-rpath,$ORIGIN/../lib" "-Wl,-rpath,/usr/local/lib/rustlib/x86_64-unknown-linux-gnu/lib" "-l" "compiler-rt"
note: /var/tmp/portage/dev-lang/rust-1.7.0/work/rustc-1.7.0/x86_64-unknown-linux-gnu/stage0/lib/rustlib/x86_64-unknown-linux-gnu/lib/librustc_trans-6a154fe0.so: undefined reference to `LLVMCloneModule'
collect2: error: ld returned 1 exit status

[dotdash]

Oh, that's from my fix for emitting mulitple formats at once, I didn't realize that LLVMCloneModule was new in 3.6

[alexcrichton]

Ah no worries! We still don't have many requests for specifically older LLVM versions and we're not committed to supporting LLVM 3.5, so this seems fine (especially now that it's been tracked down)

@bors: r+ ed28247

Thanks!

[bors]

⌛ Testing commit ed28247 with merge c9b6ba8...

[bors]

☀️ Test successful - auto-linux-32-nopt-t, auto-linux-32-opt, auto-linux-64-debug-opt, auto-linux-64-nopt-t, auto-linux-64-opt, auto-linux-64-opt-mir, auto-linux-64-opt-rustbuild, auto-linux-64-x-android-t, auto-linux-64-x-armhf, auto-linux-64-x-armsf, auto-linux-64-x-freebsd, auto-linux-64-x-netbsd, auto-linux-cross-opt, auto-linux-musl-64-opt, auto-mac-32-opt, auto-mac-64-nopt-t, auto-mac-64-opt, auto-mac-ios-opt, auto-win-gnu-32-nopt-t, auto-win-gnu-32-opt, auto-win-gnu-32-opt-rustbuild, auto-win-gnu-64-nopt-t, auto-win-gnu-64-opt, auto-win-msvc-32-opt, auto-win-msvc-64-opt, auto-win-msvc-64-opt-mir, auto-win-msvc-64-opt-rustbuild