[beta] rustc_const_math: undefined reference to `rust_eh_personality'

[cuviper]

While testing 1.16.0-beta.3 builds on Fedora, I'm getting a link error for rust_eh_personality on i686 and armv7hl, but not on the rest of arches which are all 64-bit. I'm also seeing this only on Fedora 24/25 with LLVM-3.8, not on Fedora rawhide with LLVM-3.9.

   Compiling rustc_const_math v0.0.0 (file:///builddir/build/BUILD/rustc-beta-src/src/librustc_const_math)
error: linking with `cc` failed: exit code: 1
  |
  = note: "cc" "-Wl,--as-needed" "-Wl,-z,noexecstack" "-m32" "-L" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1/lib/rustlib/i686-unknown-linux-gnu/lib" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1-rustc/i686-unknown-linux-gnu/release/deps/rustc_const_math-3eb308102ead4d97.0.o" "-o" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1-rustc/i686-unknown-linux-gnu/release/deps/librustc_const_math-3eb308102ead4d97.so" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1-rustc/i686-unknown-linux-gnu/release/deps/rustc_const_math-3eb308102ead4d97.metadata.o" "-Wl,-O1" "-nodefaultlibs" "-L" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1-rustc/i686-unknown-linux-gnu/release/deps" "-L" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1-rustc/release/deps" "-L" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1/lib/rustlib/i686-unknown-linux-gnu/lib" "-Wl,-Bstatic" "-Wl,-Bdynamic" "-L" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1-rustc/i686-unknown-linux-gnu/release/deps" "-l" "syntax-361284d4f5fb5940" "-L" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1-rustc/i686-unknown-linux-gnu/release/deps" "-l" "rustc_data_structures-b6582de1b9706e19" "-L" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1-rustc/i686-unknown-linux-gnu/release/deps" "-l" "rustc_errors-11fbf09a24007839" "-L" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1-rustc/i686-unknown-linux-gnu/release/deps" "-l" "log-15b4e8336a0a4a4a" "-L" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1/lib/rustlib/i686-unknown-linux-gnu/lib" "-l" "term-1f8b28580ffa517e" "-L" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1-rustc/i686-unknown-linux-gnu/release/deps" "-l" "syntax_pos-091c6cfef6161c2c" "-L" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1-rustc/i686-unknown-linux-gnu/release/deps" "-l" "serialize-41fa6f76166d8a6e" "-L" "/builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1/lib/rustlib/i686-unknown-linux-gnu/lib" "-l" "std-675d08ed24b25a61" "/tmp/rustc.QQnGwqNawKRQ/libcompiler_builtins-55bf5e5eafc786cf.rlib" "-l" "dl" "-l" "rt" "-l" "pthread" "-l" "gcc_s" "-l" "c" "-l" "m" "-l" "rt" "-l" "util" "-shared" "-Wl,-z,relro,-z,now"
  = note: /builddir/build/BUILD/rustc-beta-src/build/i686-unknown-linux-gnu/stage1-rustc/i686-unknown-linux-gnu/release/deps/rustc_const_math-3eb308102ead4d97.0.o:(.data.DW.ref.rust_eh_personality[DW.ref.rust_eh_personality]+0x0): undefined reference to `rust_eh_personality'
          collect2: error: ld returned 1 exit status


error: aborting due to previous error

error: Could not compile `rustc_const_math`.

The problem seems exactly like that described in commit 92e6c53, part of #38482. On the F25 system, the stage1 libcompiler_builtins.rlib contains undefined references to rust_eh_personality, and the working rawhide system does not. I don't know how they identified where the reference is coming from, but since this seems dependent on the LLVM version, I guess there's still some missing optimization or analysis that needs to be cleaned up.

cc @est31 @nagisa

[cuviper]

Here are the two libraries, where llvm38 fails and llvm39 works:
rust40251-libcompiler_builtins.zip

[cuviper]

That commit describes this only happening with optimizations turned off, but I do have optimization on. I also have debuginfo on, in case that matters. I also see a DW.ref.rust_eh_personality, but I'm not sure if that's relevant.

[est31]

@cuviper can you upload the binary somewhere? EDIT: oh, seems you did. Debuginfo turned on is really great, it can help us nail down the offender.

Also, have you turned debug assertions on? If yes, maybe try turning them off.

[cuviper]

I don't think I have debug assertions - at least not in config.mk, just CFG_ENABLE_DEBUGINFO := 1.

[nagisa]

I also see a DW.ref.rust_eh_personality, but I'm not sure if that's relevant.

It is. That’s the thing which preserves the only reference to rust_eh_personality. I’m not sure why it remanins, but it shouldn’t be present in the first place.

[Mark-Simulacrum]

@cuviper confirmed fixed in #40254.