[Pkg-rust-maintainers] Bug#897854: rustc: ftbfs with GCC-8

[Matthias Klose]

Package: src:rustc
Version: 1.24.1+dfsg1-1
Severity: normal
Tags: sid buster
User: debian-gcc at lists.debian.org
Usertags: ftbfs-gcc-8

Please keep this issue open in the bug tracker for the package it
was filed for.  If a fix in another package is required, please
file a bug for the other package (or clone), and add a block in this
package. Please keep the issue open until the package can be built in
a follow-up test rebuild.

The package fails to build in a test rebuild on at least amd64 with
gcc-8/g++-8, but succeeds to build with gcc-7/g++-7. The
severity of this report will be raised before the buster release.

The full build log can be found at:
http://aws-logs.debian.net/2018/05/01/gcc8/rustc_1.24.1+dfsg1-1_unstable_gcc8.log.gz
The last lines of the build log are at the end of this report.

To build with GCC 8, either set CC=gcc-8 CXX=g++-8 explicitly,
or install the gcc, g++, gfortran, ... packages from experimental.

  apt-get -t=experimental install g++ 

Common build failures are new warnings resulting in build failures with
-Werror turned on, or new/dropped symbols in Debian symbols files.
For other C/C++ related build failures see the porting guide at
http://gcc.gnu.org/gcc-8/porting_to.html

[...]
warning:      struct pair
warning:             ^~~~
error: build failed
thread 'main' panicked at 'command did not execute successfully: "/usr/bin/cargo" "build" "--target" "x86_64-unknown-linux-gnu" "-v" "--release" "--features" " llvm" "--manifest-path" "/<<BUILDDIR>>/rustc-1.24.1+dfsg1/src/rustc/Cargo.toml" "--message-format" "json"
expected success, got: exit code: 101', bootstrap/compile.rs:880:9
stack backtrace:
   0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace
   1: std::sys_common::backtrace::print
   2: std::panicking::default_hook::{{closure}}
   3: std::panicking::default_hook
   4: std::panicking::rust_panic_with_hook
   5: std::panicking::begin_panic
   6: std::panicking::begin_panic_fmt
   7: bootstrap::compile::run_cargo
   8: <bootstrap::compile::Rustc as bootstrap::builder::Step>::run
   9: bootstrap::builder::Builder::ensure
  10: <bootstrap::compile::Assemble as bootstrap::builder::Step>::run
  11: bootstrap::builder::Builder::ensure
  12: bootstrap::builder::Builder::compiler
  13: <bootstrap::compile::Assemble as bootstrap::builder::Step>::run
  14: bootstrap::builder::Builder::ensure
  15: bootstrap::builder::Builder::compiler
  16: <bootstrap::compile::Std as bootstrap::builder::Step>::make_run
  17: bootstrap::builder::StepDescription::maybe_run
  18: bootstrap::builder::StepDescription::run
  19: bootstrap::builder::Builder::run
  20: bootstrap::Build::build
  21: bootstrap::main
  22: std::rt::lang_start::{{closure}}
  23: std::panicking::try::do_call
  24: __rust_maybe_catch_panic
  25: std::rt::lang_start_internal
  26: std::rt::lang_start
  27: main
  28: __libc_start_main
  29: _start
Traceback (most recent call last):
  File "./x.py", line 20, in <module>
    bootstrap.main()
  File "/<<BUILDDIR>>/rustc-1.24.1+dfsg1/src/bootstrap/bootstrap.py", line 755, in main
    bootstrap()
  File "/<<BUILDDIR>>/rustc-1.24.1+dfsg1/src/bootstrap/bootstrap.py", line 746, in bootstrap
    run(args, env=env, verbose=build.verbose)
  File "/<<BUILDDIR>>/rustc-1.24.1+dfsg1/src/bootstrap/bootstrap.py", line 149, in run
    raise RuntimeError(err)
RuntimeError: failed to run: /<<BUILDDIR>>/rustc-1.24.1+dfsg1/build/bootstrap/debug/bootstrap build --config debian/config.toml -v --on-fail env
make[1]: *** [debian/rules:207: override_dh_auto_build-arch] Error 1
make[1]: Leaving directory '/<<BUILDDIR>>/rustc-1.24.1+dfsg1'
make: *** [debian/rules:143: build-arch] Error 2
dpkg-buildpackage: error: debian/rules build-arch subprocess returned exit status 2