Compiler crashes with SIGSEGV when compiling core library with static relocation model

[Serentty]

So, I'm compiling Rust programs to run on MS-DOS (386 real mode). This requires a static relocation model, and I can get many programs to compile and run by passing -C relocation-model=static during compilation and making sure that my linker flags include -fno-pie. However, things went wrong when I tried to hook the I/O routines that I had written up to Rust's formatting macros. Trait implementations for core::fmt::Arguments start to get pulled in, and the linker complains that they are looking for GLOBAL_OFFSET_TABLE despite the fact that the compiler shouldn't be generating code which needs that.

error: linking with `cc` failed: exit code: 1
  |
  = note: "cc" "-Wl,--as-needed" "-Wl,-z,noexecstack" "-Wl,--gc-sections" "-m16" "-nostdlib" "-march=i386" "-ffreestanding" "-fno-pie" "-Tcom.ld" "-L" "/home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib" "/home/seren/rusty-dos/target/dos/release/deps/dos-81645608ce9864b6.dos.dg1u0jr4-cgu.0.rcgu.o" "/home/seren/rusty-dos/target/dos/release/deps/dos-81645608ce9864b6.dos.dg1u0jr4-cgu.1.rcgu.o" "/home/seren/rusty-dos/target/dos/release/deps/dos-81645608ce9864b6.dos.dg1u0jr4-cgu.2.rcgu.o" "/home/seren/rusty-dos/target/dos/release/deps/dos-81645608ce9864b6.dos.dg1u0jr4-cgu.3.rcgu.o" "/home/seren/rusty-dos/target/dos/release/deps/dos-81645608ce9864b6.dos.dg1u0jr4-cgu.4.rcgu.o" "/home/seren/rusty-dos/target/dos/release/deps/dos-81645608ce9864b6.dos.dg1u0jr4-cgu.5.rcgu.o" "/home/seren/rusty-dos/target/dos/release/deps/dos-81645608ce9864b6.dos.dg1u0jr4-cgu.6.rcgu.o" "-o" "/home/seren/rusty-dos/target/dos/release/deps/dos-81645608ce9864b6.com" "-Wl,--gc-sections" "-no-pie" "-Wl,-zrelro" "-Wl,-znow" "-nodefaultlibs" "-L" "/home/seren/rusty-dos/target/dos/release/deps" "-L" "/home/seren/rusty-dos/target/release/deps" "-L" "/home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib" "-Wl,-Bstatic" "/home/seren/rusty-dos/target/dos/release/deps/libbitflags-e1a464dc3e355838.rlib" "/home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/librustc_std_workspace_core-490848ebf202e93d.rlib" "/home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib" "/home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcompiler_builtins-ae809761299d8c44.rlib" "-Wl,-Bdynamic"
  = note: /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.5.rcgu.o): in function `_ZN4core3fmt10ArgumentV110show_usize17h9290b20043846a9aE.llvm.11768198070876224222':
          core.dffyupwt-cgu.5:(.text._ZN4core3fmt10ArgumentV110show_usize17h9290b20043846a9aE.llvm.11768198070876224222+0x17): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.5.rcgu.o): in function `core::fmt::ArgumentV1::from_usize':
          core.dffyupwt-cgu.5:(.text._ZN4core3fmt10ArgumentV110from_usize17h306ac2fc1d8b66c1E+0xb): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.5.rcgu.o): in function `<core::fmt::Arguments as core::fmt::Debug>::fmt':
          core.dffyupwt-cgu.5:(.text._ZN57_$LT$core..fmt..Arguments$u20$as$u20$core..fmt..Debug$GT$3fmt17h00de601147a33c89E+0x1c): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.5.rcgu.o): in function `<core::fmt::Arguments as core::fmt::Display>::fmt':
          core.dffyupwt-cgu.5:(.text._ZN59_$LT$core..fmt..Arguments$u20$as$u20$core..fmt..Display$GT$3fmt17h8229c189564c851aE+0x1c): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.5.rcgu.o): in function `core::fmt::write':
          core.dffyupwt-cgu.5:(.text._ZN4core3fmt5write17h1c6a04dbcbef5dc7E+0x82): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.5.rcgu.o):core.dffyupwt-cgu.5:(.text._ZN4core3fmt9Formatter8wrap_buf17hf8f3027e075f5fd5E+0xd0): more undefined references to `_GLOBAL_OFFSET_TABLE_' follow
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.12.rcgu.o): in function `<core::sync::atomic::AtomicI64 as core::fmt::Debug>::fmt':
          core.dffyupwt-cgu.12:(.text._ZN66_$LT$core..sync..atomic..AtomicI64$u20$as$u20$core..fmt..Debug$GT$3fmt17hbc9f32d54d630799E+0x35): undefined reference to `__atomic_load_8'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.12.rcgu.o): in function `<core::sync::atomic::AtomicU64 as core::fmt::Debug>::fmt':
          core.dffyupwt-cgu.12:(.text._ZN66_$LT$core..sync..atomic..AtomicU64$u20$as$u20$core..fmt..Debug$GT$3fmt17h2bacc92521ff782aE+0x1a): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: core.dffyupwt-cgu.12:(.text._ZN66_$LT$core..sync..atomic..AtomicU64$u20$as$u20$core..fmt..Debug$GT$3fmt17h2bacc92521ff782aE+0x3a): undefined reference to `__atomic_load_8'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.12.rcgu.o): in function `<&T as core::fmt::Debug>::fmt':
          core.dffyupwt-cgu.12:(.text._ZN42_$LT$$RF$T$u20$as$u20$core..fmt..Debug$GT$3fmt17h05f349f183bd57f5E+0x1e): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.12.rcgu.o): in function `<&T as core::fmt::Debug>::fmt':
          core.dffyupwt-cgu.12:(.text._ZN42_$LT$$RF$T$u20$as$u20$core..fmt..Debug$GT$3fmt17h1feb199478027b45E+0x1e): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.12.rcgu.o): in function `<&T as core::fmt::Debug>::fmt':
          core.dffyupwt-cgu.12:(.text._ZN42_$LT$$RF$T$u20$as$u20$core..fmt..Debug$GT$3fmt17h25a1d98a3ec158d7E+0xd): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.12.rcgu.o): in function `<&T as core::fmt::Debug>::fmt':
          core.dffyupwt-cgu.12:(.text._ZN42_$LT$$RF$T$u20$as$u20$core..fmt..Debug$GT$3fmt17h2ca09666842d4c7eE+0x1a): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.12.rcgu.o): in function `<&T as core::fmt::Debug>::fmt':
          core.dffyupwt-cgu.12:(.text._ZN42_$LT$$RF$T$u20$as$u20$core..fmt..Debug$GT$3fmt17h348ad87268046417E+0x1e): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcore-86783f30f14d1df7.rlib(core-86783f30f14d1df7.core.dffyupwt-cgu.12.rcgu.o):core.dffyupwt-cgu.12:(.text._ZN42_$LT$$RF$T$u20$as$u20$core..fmt..Debug$GT$3fmt17h3eb6f5e1d37d7ffdE+0x1e): more undefined references to `_GLOBAL_OFFSET_TABLE_' follow
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcompiler_builtins-ae809761299d8c44.rlib(compiler_builtins-ae809761299d8c44.compiler_builtins.85hciet7-cgu.7.rcgu.o): in function `__llvm_memcpy_element_unordered_atomic_8':
          compiler_builtins.85hciet7-cgu.7:(.text.__llvm_memcpy_element_unordered_atomic_8+0x47): undefined reference to `__atomic_load_8'
          /usr/sbin/ld: compiler_builtins.85hciet7-cgu.7:(.text.__llvm_memcpy_element_unordered_atomic_8+0x5a): undefined reference to `__atomic_store_8'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcompiler_builtins-ae809761299d8c44.rlib(compiler_builtins-ae809761299d8c44.compiler_builtins.85hciet7-cgu.7.rcgu.o): in function `__llvm_memmove_element_unordered_atomic_8':
          compiler_builtins.85hciet7-cgu.7:(.text.__llvm_memmove_element_unordered_atomic_8+0x15): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: compiler_builtins.85hciet7-cgu.7:(.text.__llvm_memmove_element_unordered_atomic_8+0x5a): undefined reference to `__atomic_load_8'
          /usr/sbin/ld: compiler_builtins.85hciet7-cgu.7:(.text.__llvm_memmove_element_unordered_atomic_8+0x6d): undefined reference to `__atomic_store_8'
          /usr/sbin/ld: compiler_builtins.85hciet7-cgu.7:(.text.__llvm_memmove_element_unordered_atomic_8+0xa7): undefined reference to `__atomic_load_8'
          /usr/sbin/ld: compiler_builtins.85hciet7-cgu.7:(.text.__llvm_memmove_element_unordered_atomic_8+0xba): undefined reference to `__atomic_store_8'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcompiler_builtins-ae809761299d8c44.rlib(compiler_builtins-ae809761299d8c44.compiler_builtins.85hciet7-cgu.7.rcgu.o): in function `__llvm_memset_element_unordered_atomic_8':
          compiler_builtins.85hciet7-cgu.7:(.text.__llvm_memset_element_unordered_atomic_8+0x17): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: compiler_builtins.85hciet7-cgu.7:(.text.__llvm_memset_element_unordered_atomic_8+0xaf): undefined reference to `__atomic_store_8'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcompiler_builtins-ae809761299d8c44.rlib(compiler_builtins-ae809761299d8c44.compiler_builtins.85hciet7-cgu.10.rcgu.o): in function `__divdi3':
          compiler_builtins.85hciet7-cgu.10:(.text.__divdi3+0x13): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcompiler_builtins-ae809761299d8c44.rlib(compiler_builtins-ae809761299d8c44.compiler_builtins.85hciet7-cgu.10.rcgu.o): in function `__divti3':
          compiler_builtins.85hciet7-cgu.10:(.text.__divti3+0x1e): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcompiler_builtins-ae809761299d8c44.rlib(compiler_builtins-ae809761299d8c44.compiler_builtins.85hciet7-cgu.10.rcgu.o): in function `__moddi3':
          compiler_builtins.85hciet7-cgu.10:(.text.__moddi3+0x11): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcompiler_builtins-ae809761299d8c44.rlib(compiler_builtins-ae809761299d8c44.compiler_builtins.85hciet7-cgu.10.rcgu.o): in function `__modti3':
          compiler_builtins.85hciet7-cgu.10:(.text.__modti3+0x1e): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          /usr/sbin/ld: /home/seren/rusty-dos/target/sysroot/lib/rustlib/dos/lib/libcompiler_builtins-ae809761299d8c44.rlib(compiler_builtins-ae809761299d8c44.compiler_builtins.85hciet7-cgu.10.rcgu.o): in function `__divmoddi4':
          compiler_builtins.85hciet7-cgu.10:(.text.__divmoddi4+0x13): undefined reference to `_GLOBAL_OFFSET_TABLE_'
          collect2: error: ld returned 1 exit status

[nagisa]

Are you sure you compile libcore and other sysroot crates with -Crelocation-model=static?

[Serentty]

@nagisa The code is here, including the target JSON file. There isn't any code committed which causes this error, but this can be reproduced by simply downloading that repository, adding a few lines trying to use formatting macros, and building it according to the instructions. This is the command I'm using to build.

RUSTFLAGS="-C opt-level=z -C relocation-model=static" cargo xbuild --release --target dos.json

There's always a chance that Cargo XBuild isn't respecting RUSTFLAGS when compiling the core library. That's a possibility that I should look into.

[nagisa]

It should be fairly easy to verify by asking cargo to output compiler invocations with --verbose

[Serentty]

Aha! It only adds the flags to my own crate and its explicit dependencies, not to the core and builtin libraries that it builds automatically. I'll see if I can figure out how to get those built with my flags, and if that doesn't generate this stuff, I'll go ahead and close this issue.

[Serentty]

@nagisa So, I've figured that out, but I seem to have run into a more serious issue. The compiler crashes on an invalid memory reference when trying to build core with a static relocation model.

error: could not compile `core`.

Caused by:
  process didn't exit successfully: `rustc --crate-name core --edition=2018 /home/seren/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libcore/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type rlib --emit=dep-info,metadata,link -C opt-level=3 -C panic=abort -C metadata=b3b8d14870eb83b9 -C extra-filename=-b3b8d14870eb83b9 --out-dir /home/seren/rusty-dos/target/dos/release/deps --target /home/seren/rusty-dos/dos.json -Zforce-unstable-if-unmarked -L dependency=/home/seren/rusty-dos/target/dos/release/deps -L dependency=/home/seren/rusty-dos/target/release/deps -C opt-level=z -C relocation-model=static` (signal: 11, SIGSEGV: invalid memory reference)
warning: build failed, waiting for other jobs to finish...
error: build failed

The command:

RUSTFLAGS="-C opt-level=z -C relocation-model=static" cargo build -Z build-std --release --target dos.json

[nagisa]

This is most likely a llvm assertion, those produce sigsegvs by default for performance reasons.

…

On Mon, 20 Jan 2020, 21:31 Serentty, ***@***.***> wrote: @nagisa <https://github.com/nagisa> So, I've figured that out, but I seem to have run into a more serious issue. The compiler crashes on an invalid memory reference when trying to build core with a static relocation model. error: could not compile `core`. Caused by: process didn't exit successfully: `rustc --crate-name core --edition=2018 /home/seren/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/src/rust/src/libcore/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type rlib --emit=dep-info,metadata,link -C opt-level=3 -C panic=abort -C metadata=b3b8d14870eb83b9 -C extra-filename=-b3b8d14870eb83b9 --out-dir /home/seren/rusty-dos/target/dos/release/deps --target /home/seren/rusty-dos/dos.json -Zforce-unstable-if-unmarked -L dependency=/home/seren/rusty-dos/target/dos/release/deps -L dependency=/home/seren/rusty-dos/target/release/deps -C opt-level=z -C relocation-model=static` (signal: 11, SIGSEGV: invalid memory reference) warning: build failed, waiting for other jobs to finish... error: build failed — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#68323?email_source=notifications&email_token=AAFFZUQ4ZHS547NPACYBG4TQ6X3ZNA5CNFSM4KIOEUHKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEJNT2BY#issuecomment-576404743>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAFFZUUYBMJJ4KFEIZVRGQDQ6X3ZNANCNFSM4KIOEUHA> .

[Serentty]

This would still be some sort of bug though, right? Either Rust is passing in malformed data that doesn't meet LLVM's assumptions, or LLVM itself has an issue.

[nagisa]

Yes.

…

On Tue, 21 Jan 2020, 05:13 Serentty, ***@***.***> wrote: This would still be some sort of bug though, right? Either Rust is passing in malformed data that doesn't meet LLVM's assumptions, or LLVM itself has an issue. — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#68323?email_source=notifications&email_token=AAFFZUSY35LR573Q5CRUFZLQ6ZR5FA5CNFSM4KIOEUHKYY3PNVWWK3TUL52HS4DFVREXG43VMVBW63LNMVXHJKTDN5WW2ZLOORPWSZGOEJOLAWQ#issuecomment-576499802>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AAFFZUSIJSQA2PNPKODLDZ3Q6ZR5FANCNFSM4KIOEUHA> .

[nagisa]

You’ll need to build the compiler with LLVM assertions enabled and extract the backtrace (could also do it on the regular build, although knowing what assertion fired is still useful and beneficial)

[Serentty]

Alright, I'll try to do that soon. Meanwhile I'll rename this issue to reflect the current problem.

[helinwang]

I got similar error, but the problem went away after running cargo build --release again:

error: could not compile `ra_ide_db`.

Caused by:
  process didn't exit successfully: `rustc --crate-name ra_ide_db --edition=2018 crates/ra_ide_db/src/lib.rs --error-format=json --json=diagnostic-rendered-ansi,artifacts --crate-type lib --emit=dep-info,metadata,link -C opt-level=3 -Cembed-bitcode=no -C debuginfo=0 -C metadata=1b26a821a979b7f0 -C extra-filename=-1b26a821a979b7f0 --out-dir /home/helin/repos/rust-analyzer/target/release/deps -C incremental=/home/helin/repos/rust-analyzer/target/release/incremental -L dependency=/home/helin/repos/rust-analyzer/target/release/deps --extern either=/home/helin/repos/rust-analyzer/target/release/deps/libeither-aa67f500fa1b3836.rmeta --extern fst=/home/helin/repos/rust-analyzer/target/release/deps/libfst-a436241aaecda5dd.rmeta --extern log=/home/helin/repos/rust-analyzer/target/release/deps/liblog-d65b441cd99ca94f.rmeta --extern once_cell=/home/helin/repos/rust-analyzer/target/release/deps/libonce_cell-1f1d61fb9d888693.rmeta --extern ra_db=/home/helin/repos/rust-analyzer/target/release/deps/libra_db-a1580ba10ebdaadf.rmeta --extern hir=/home/helin/repos/rust-analyzer/target/release/deps/libra_hir-65194feebe637091.rmeta --extern ra_prof=/home/helin/repos/rust-analyzer/target/release/deps/libra_prof-121a6d18eb447714.rmeta --extern ra_syntax=/home/helin/repos/rust-analyzer/target/release/deps/libra_syntax-40f70cf46f5a35df.rmeta --extern ra_text_edit=/home/helin/repos/rust-analyzer/target/release/deps/libra_text_edit-72023d99c13fe359.rmeta --extern rayon=/home/helin/repos/rust-analyzer/target/release/deps/librayon-14c5f6912a720164.rmeta --extern rustc_hash=/home/helin/repos/rust-analyzer/target/release/deps/librustc_hash-0d698360b305d6d8.rmeta --extern superslice=/home/helin/repos/rust-analyzer/target/release/deps/libsuperslice-4f6adebb3fcb1bf0.rmeta --extern test_utils=/home/helin/repos/rust-analyzer/target/release/deps/libtest_utils-e498bb2e216f0313.rmeta` (signal: 11, SIGSEGV: invalid memory reference)
warning: build failed, waiting for other jobs to finish...
remark: <unknown>:0:0: loop not vectorized: loop control flow is not understood by vectorizer
remark: <unknown>:0:0: loop not vectorized: loop control flow is not understood by vectorizer
remark: <unknown>:0:0: loop not vectorized: loop control flow is not understood by vectorizer
error: build failed
➜  rust-analyzer git:(master) cargo build --release
   Compiling ra_ide_db v0.1.0 (/home/helin/repos/rust-analyzer/crates/ra_ide_db)
   Compiling ra_ssr v0.1.0 (/home/helin/repos/rust-analyzer/crates/ra_ssr)
   Compiling ra_assists v0.1.0 (/home/helin/repos/rust-analyzer/crates/ra_assists)
   Compiling ra_ide v0.1.0 (/home/helin/repos/rust-analyzer/crates/ra_ide)
   Compiling rust-analyzer v0.1.0 (/home/helin/repos/rust-analyzer/crates/rust-analyzer)

rustc --version     
rustc 1.46.0-nightly (f844ea1e5 2020-07-03)