Bitode fembed-bitcode-marker breaking iOS debug builds

[kali]

Hi,

It looks like the -fembed-bitcode-marker breaks the debug builds (it is not set on release bug).

To be honest, I'm not 100% sure where the actual issue is, but something looses track of the actually compiled symbols somewhere.

Here is a test-case. A rust wrapper library with a -sys underneath (with a void native_function() {} ), try to build test on the rusty wrapper.

First run: native, macos for reference.
Second run: test targetting ios, missing symbols while linking.
Third run: same with --release, disabling the fembed-bitcode-marker as a side effect, it compiles.

Forcing cc back to 1.0.5 make the probelm disappear. Or Using a patched cc-rs that do not put the bintcode-marker.

S 15/03 9:42 ~/dev/snips/tc-init-bitcode-marker% cargo test
   Compiling cc v1.0.7
   Compiling tc-init-bitcode-marker-sys v0.1.0 (file:///Users/kali/dev/snips/tc-init-bitcode-marker/tc-init-bitcode-marker-sys)
   Compiling tc-init-bitcode-marker v0.1.0 (file:///Users/kali/dev/snips/tc-init-bitcode-marker)
    Finished dev [unoptimized + debuginfo] target(s) in 2.73 secs
     Running target/debug/deps/tc_init_bitcode_marker-c331333640f6d205

running 1 test
test tests::it_works ... ok

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

   Doc-tests tc-init-bitcode-marker

running 0 tests

test result: ok. 0 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out

S 15/03 9:42 ~/dev/snips/tc-init-bitcode-marker% TARGET_SYSROOT=`xcrun -sdk iphoneos --show-sdk-path` cargo test --target aarch64-apple-ios
   Compiling tc-init-bitcode-marker-sys v0.1.0 (file:///Users/kali/dev/snips/tc-init-bitcode-marker/tc-init-bitcode-marker-sys)
   Compiling tc-init-bitcode-marker v0.1.0 (file:///Users/kali/dev/snips/tc-init-bitcode-marker)
error: linking with `cc` failed: exit code: 1
  |
  = note: "cc" "-arch" "arm64" "-Wl,-syslibroot" "/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS11.2.sdk" "-L" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib" "/Users/kali/dev/snips/tc-init-bitcode-marker/target/aarch64-apple-ios/debug/deps/tc_init_bitcode_marker-5b76daec38646eb8.1bi40wzgjfa2z8fe.rcgu.o" "/Users/kali/dev/snips/tc-init-bitcode-marker/target/aarch64-apple-ios/debug/deps/tc_init_bitcode_marker-5b76daec38646eb8.1y16o1qfye96o7m0.rcgu.o" "/Users/kali/dev/snips/tc-init-bitcode-marker/target/aarch64-apple-ios/debug/deps/tc_init_bitcode_marker-5b76daec38646eb8.2k322vp0xntl1vb2.rcgu.o" "/Users/kali/dev/snips/tc-init-bitcode-marker/target/aarch64-apple-ios/debug/deps/tc_init_bitcode_marker-5b76daec38646eb8.3rngp6bm2u2q5z0y.rcgu.o" "/Users/kali/dev/snips/tc-init-bitcode-marker/target/aarch64-apple-ios/debug/deps/tc_init_bitcode_marker-5b76daec38646eb8.twro57p54np36np.rcgu.o" "-o" "/Users/kali/dev/snips/tc-init-bitcode-marker/target/aarch64-apple-ios/debug/deps/tc_init_bitcode_marker-5b76daec38646eb8" "/Users/kali/dev/snips/tc-init-bitcode-marker/target/aarch64-apple-ios/debug/deps/tc_init_bitcode_marker-5b76daec38646eb8.crate.allocator.rcgu.o" "-Wl,-dead_strip" "-nodefaultlibs" "-L" "/Users/kali/dev/snips/tc-init-bitcode-marker/target/aarch64-apple-ios/debug/deps" "-L" "/Users/kali/dev/snips/tc-init-bitcode-marker/target/debug/deps" "-L" "/Users/kali/dev/snips/tc-init-bitcode-marker/target/aarch64-apple-ios/debug/build/tc-init-bitcode-marker-sys-bcd7b7491fb82c24/out" "-L" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib" "/Users/kali/dev/snips/tc-init-bitcode-marker/target/aarch64-apple-ios/debug/deps/libtc_init_bitcode_marker_sys-f1d44cb505be7d46.rlib" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib/libtest-24fa6627a68aaf09.rlib" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib/libterm-18625f57bc60e498.rlib" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib/libgetopts-85228cbd7e544789.rlib" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib/libstd-df91e356061f8ac8.rlib" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib/libpanic_unwind-1086e1d0e6cd90ef.rlib" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib/libunwind-ce923fc11d74f968.rlib" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib/liballoc_system-e87ca03f4215e4ef.rlib" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib/liblibc-e959e9c0d1548c0e.rlib" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib/liballoc-37638280ec40d743.rlib" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib/libstd_unicode-0766335b25639e9e.rlib" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib/libcore-e1a6bc6fd1c79bbc.rlib" "/Users/kali/.rustup/toolchains/stable-x86_64-apple-darwin/lib/rustlib/aarch64-apple-ios/lib/libcompiler_builtins-c410c86b18328824.rlib" "-l" "System" "-l" "objc" "-framework" "Security" "-framework" "Foundation" "-l" "resolv" "-l" "c" "-l" "m"
  = note: Undefined symbols for architecture arm64:
            "_native_function", referenced from:
                tc_init_bitcode_marker::call_it::h8098132b2999850c in tc_init_bitcode_marker-5b76daec38646eb8.1bi40wzgjfa2z8fe.rcgu.o
          ld: symbol(s) not found for architecture arm64
          clang: error: linker command failed with exit code 1 (use -v to see invocation)


error: aborting due to previous error

error: Could not compile `tc-init-bitcode-marker`.

To learn more, run the command again with --verbose.
[1]    55263 exit 101   TARGET_SYSROOT=`xcrun -sdk iphoneos --show-sdk-path` cargo test --target
S 15/03 9:42 ~/dev/snips/tc-init-bitcode-marker% TARGET_SYSROOT=`xcrun -sdk iphoneos --show-sdk-path` cargo test --target aarch64-apple-ios  --release
   Compiling cc v1.0.7
   Compiling tc-init-bitcode-marker-sys v0.1.0 (file:///Users/kali/dev/snips/tc-init-bitcode-marker/tc-init-bitcode-marker-sys)
   Compiling tc-init-bitcode-marker v0.1.0 (file:///Users/kali/dev/snips/tc-init-bitcode-marker)
    Finished release [optimized] target(s) in 5.20 secs
     Running target/aarch64-apple-ios/release/deps/tc_init_bitcode_marker-5701cd311fc4ffc2
error: could not execute process `/Users/kali/dev/snips/tc-init-bitcode-marker/target/aarch64-apple-ios/release/deps/tc_init_bitcode_marker-5701cd311fc4ffc2` (never executed)

Caused by:
  Bad CPU type in executable (os error 86)
[1]    55299 exit 101   TARGET_SYSROOT=`xcrun -sdk iphoneos --show-sdk-path` cargo test --target

[kali]

tc-init-bitcode-marker.zip

[kali]

I was able to do a few more tests while investigating the issue. Specifically, nm do not see any symbol in both static libraries formed when the option is set (the .a and the .rlib)

S 15/03 9:53 ~/dev/snips/tc-init-bitcode-marker% nm target/aarch64-apple-ios/debug/build/tc-init-bitcode-marker-sys-10a81f0c360f171f/out/libfoo.a
S 15/03 9:53 ~/dev/snips/tc-init-bitcode-marker% nm target/aarch64-apple-ios/debug/deps/libtc_init_bitcode_marker_sys-1c0d20b841b3adaa.rlib

target/aarch64-apple-ios/debug/deps/libtc_init_bitcode_marker_sys-1c0d20b841b3adaa.rlib(tc_init_bitcode_marker_sys-1c0d20b841b3adaa.1y16o1qfye96o7m0.rcgu.o):
0000000000000000 t ltmp0
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/nm: target/aarch64-apple-ios/debug/deps/libtc_init_bitcode_marker_sys-1c0d20b841b3adaa.rlib(rust.metadata.bin) The end of the file was unexpectedly encountered

S 15/03 9:53 ~/dev/snips/tc-init-bitcode-marker% nm target/aarch64-apple-ios/debug/deps/libtc_init_bitcode_marker-270d3cfb64419d79.rlib

target/aarch64-apple-ios/debug/deps/libtc_init_bitcode_marker-270d3cfb64419d79.rlib(tc_init_bitcode_marker-270d3cfb64419d79.1bi40wzgjfa2z8fe.rcgu.o):
0000000000000000 T __ZN22tc_init_bitcode_marker7call_it17h3e65230248e881c3E
                 U _native_function
0000000000000000 t ltmp0
0000000000000258 s ltmp1
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/nm: target/aarch64-apple-ios/debug/deps/libtc_init_bitcode_marker-270d3cfb64419d79.rlib(rust.metadata.bin) The end of the file was unexpectedly encountered

[1]    56122 exit 1     nm
S 15/03 9:53 ~/dev/snips/tc-init-bitcode-marker% nm target/aarch64-apple-ios/debug/build/tc-init-bitcode-marker-sys-10a81f0c360f171f/out/libfoo.a

[kali]

I think we should probably not put this second option automatically. The --enable-bitcode do not look like a problem.

[alexcrichton]

cc @comex and @michaeleiselsc, would y'all be able to help diagnose what's going on here?

FWIW @kali the change here was spurred on by discussion in rust-lang/rust#35968, but I'm very unfamiliar with iOS myself :(

[michaeleiselsc]

i thought bitcode support would be disabled by default? if so, can't we just use the previous behavior unless the user has added that -Z flag for bitcode?

[alexcrichton]

@michaeleiselsc it was in Rust yeah but that was after I made this change. How would you expect to enable this for the cc crate?

[comex]

Looks like the same LLVM bug I mentioned in rust-lang/rust#48896 (comment). As I said there,

For now, as a workaround for the LLVM bug, I think the best approach is to avoid -fembed-bitcode-marker or equivalent, in both this PR and cc-rs.

I guess I should have filed an issue in this repository too…

[alexcrichton]

Ah right thanks for the heads up @comex!

This was fixed by @kali in #305 (thanks!)