bug#48239: rust-1.19.0 build fails

bug#48239: rust-1.19.0 build fails

[Bone Baboon via Bug reports for GNU Guix]

[-- Attachment #1: Type: text/plain, Size: 7137 bytes --]

On a x86_64 computer when I run `guix build --no-substitutes --cores=1 rust` it fails during the build phase of rust-1.19.0.

The build log of rust-1.19.0 is attached.

`guix describe` outputs:

```
Generation 18   May 03 2021 13:15:55    (current)
  guix 065d2cd
    repository URL: https://git.savannah.gnu.org/git/guix.git
    commit: 065d2cd6ced96ddb38c15a46f798488f61660a33
```

The error message:

```
builder for `/gnu/store/0y39y7vnjcypnc3g0j1fci9xkg186qnp-rust-1.19.0.drv' failed with exit code 1
build of /gnu/store/0y39y7vnjcypnc3g0j1fci9xkg186qnp-rust-1.19.0.drv failed
View build log at '/var/log/guix/drvs/0y/39y7vnjcypnc3g0j1fci9xkg186qnp-rust-1.19.0.drv.bz2'.
cannot build derivation `/gnu/store/zwqk3ilzckx7daq0hasfwbp7khph9f9d-rust-1.20.0.drv': 1 dependencies couldn't be built
building /gnu/store/7phnak4l2fgbgwbc13066lx3fsmszsxv-rustc-1.21.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/m7hc0d7vf8bhrm4z586n84idwbv5fydl-rust-1.21.0.drv': 1 dependencies couldn't be built
building /gnu/store/wkdjph18flyspdiq17db2b6isvx4xwr0-rustc-1.22.1-src.tar.gz.drv...
cannot build derivation `/gnu/store/lyrj2n3xyr36ryb762lhkw7hxckizcny-rust-1.22.1.drv': 1 dependencies couldn't be built
building /gnu/store/s5ylxqj197g8nw9aqga5hl19q5mhrv42-rustc-1.23.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/lm8z6al2a7dllisyri3lwkgn80r4r49a-rust-1.23.0.drv': 1 dependencies couldn't be built
building /gnu/store/jcilf8mrk6kzdi20lgsmz3g4xl4iw6j5-rustc-1.24.1-src.tar.gz.drv...
cannot build derivation `/gnu/store/cz391kmfr35bi4s85xi2rv4zz9rj4hcf-rust-1.24.1.drv': 1 dependencies couldn't be built
building /gnu/store/4xngrg3k6dgiaq81a49a2rz8wcnwvdrz-rustc-1.25.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/v8dysz7ym50yh25w20l50il7rnnv0dir-rust-1.25.0.drv': 1 dependencies couldn't be built
building /gnu/store/52ybm7q3f7cwakm1pz5w33ls2cxknidc-rustc-1.26.2-src.tar.gz.drv...
cannot build derivation `/gnu/store/zifk7csjy1bsc1bsbl3c5icnh8sbkmcm-rust-1.26.2.drv': 1 dependencies couldn't be built
building /gnu/store/z2ph48ca4kdfgz9283nb2sd63jwm0i1w-rustc-1.27.2-src.tar.gz.drv...
cannot build derivation `/gnu/store/s3yfmqgj3vn3lmy0dlqpy6qvzkp8d0k5-rust-1.27.2.drv': 1 dependencies couldn't be built
building /gnu/store/v1irclmcbhm4iv82pbcwl6g2nsxm6viy-rustc-1.28.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/3njr0x22kbx123xwh4afga3dkdm1pijq-rust-1.28.0.drv': 1 dependencies couldn't be built
building /gnu/store/vjxjzwhw1l101lz6lb1kjk9xf4r29vj2-rustc-1.29.2-src.tar.gz.drv...
cannot build derivation `/gnu/store/i7vgd09i95kbna1py0xslx5s9cd791hy-rust-1.29.2.drv': 1 dependencies couldn't be built
building /gnu/store/r0y65j9649hhrnr2mykbx3ygh0d71f24-rustc-1.30.1-src.tar.gz.drv...
cannot build derivation `/gnu/store/jcyn2rwiywj54jknc7gq2v4ljz6x1rbm-rust-1.30.1.drv': 1 dependencies couldn't be built
building /gnu/store/47qjvlvkz52c4m968nma6vjldjn3m7js-rustc-1.31.1-src.tar.gz.drv...
cannot build derivation `/gnu/store/34f7zsjy2qw0vdr6cpaia8yhj56sdns0-rust-1.31.1.drv': 1 dependencies couldn't be built
building /gnu/store/ri5gw4pksiw5v4q7b4d0r86bljrczm9f-rustc-1.32.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/22m9cfn96z67fa6451rf4400nap5n258-rust-1.32.0.drv': 1 dependencies couldn't be built
building /gnu/store/ns2cmaa8away5m72x34ny85340smqi25-rustc-1.33.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/mdkxr60f60ldfmz7wxdjj072qdl0gn1n-rust-1.33.0.drv': 1 dependencies couldn't be built
building /gnu/store/v2622arxvqm96cm5460rh96jk785z9m3-rustc-1.34.1-src.tar.gz.drv...
cannot build derivation `/gnu/store/kqiy0p1084xghwhv59g0yyzhjja8z6m6-rust-1.34.1.drv': 1 dependencies couldn't be built
building /gnu/store/pqz77bf7crv5c3yfl8ccfc4iy0h0x7hp-rustc-1.35.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/nz8qdmzk41mw6gbwan0aai1klnm7yxvz-rust-1.35.0.drv': 1 dependencies couldn't be built
building /gnu/store/q4fbfsxawvmyc74gzh7afjir1plmp06h-rustc-1.36.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/0x5s3s83wvn96qr692ln9fh4xz22dr77-rust-1.36.0.drv': 1 dependencies couldn't be built
building /gnu/store/j2sjb4791rk3x13zmpx40vv4vjv0iyik-rustc-1.37.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/x8q1naqvk5kmyg551zfmqq26hw5hnyrz-rust-1.37.0.drv': 1 dependencies couldn't be built
building /gnu/store/g3lym8f27xrmd747zqaqdc44myhp6276-rustc-1.38.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/pmnhva027xdxh80s44dqw5djlajp575k-rust-1.38.0.drv': 1 dependencies couldn't be built
building /gnu/store/c4xn6qnp282wziwpizc9p79rr56k62dm-rustc-1.39.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/asq42rd9vgdzfaza65574y0c9wr0sc8l-rust-1.39.0.drv': 1 dependencies couldn't be built
building /gnu/store/1qabnflwjr4i2nzjacr15x4l0l1siacy-rustc-1.40.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/9i23lgmj5h2l8af2qv2qm0cyxcav5ggv-rust-1.40.0.drv': 1 dependencies couldn't be built
building /gnu/store/159w3ny6qm67zamxmc60ph93m6hydvlc-rustc-1.41.1-src.tar.gz.drv...
cannot build derivation `/gnu/store/dvw1hiqkmnzhcind2svr305jnxbjx19g-rust-1.41.1.drv': 1 dependencies couldn't be built
building /gnu/store/y0bawnwasvy87pp5514kzsyn0cvm4y77-rustc-1.42.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/37rzaijk6x75fqdxx0ifm2bb3sikvyxs-rust-1.42.0.drv': 1 dependencies couldn't be built
building /gnu/store/iv1wlrydzyd9bp6g0q4gcz2vcwyds8qi-rustc-1.43.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/pc87nxz86kmmq1zc3bcay0gbhnv521k1-rust-1.43.0.drv': 1 dependencies couldn't be built
building /gnu/store/ixs8fs0zh7w6pjb9v78pslzsnrgd58r9-rustc-1.44.1-src.tar.gz.drv...
cannot build derivation `/gnu/store/21jvg5y0paq3xbwjpjq9zv1xd6qhd0ii-rust-1.44.1.drv': 1 dependencies couldn't be built
building /gnu/store/fnx7s4l000nsjzrdmmx4gs8fhsjmfq09-rustc-1.45.2-src.tar.gz.drv...
cannot build derivation `/gnu/store/bs900103rn6b3n9rgbhk5gkrcp7ff81v-rust-1.45.2.drv': 1 dependencies couldn't be built
building /gnu/store/a2pcsi5jvfzqadc6mdfi5187b88ip9ji-rustc-1.46.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/7yzcbdi423h2x5lb5bhp7mv6v0v07xbv-rust-1.46.0.drv': 1 dependencies couldn't be built
building /gnu/store/balpndimpaffj3bv2c4m70axa0djwgcg-rustc-1.47.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/p8qx13x0gqlvf1laj8qgmfdvs1ihm9yn-rust-1.47.0.drv': 1 dependencies couldn't be built
building /gnu/store/b7ld6fj67rz1kcvwvbfkri7545bgy1z2-rustc-1.48.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/6fx9sk5i20dpidbxlc4rc90l4mwfykjf-rust-1.48.0.drv': 1 dependencies couldn't be built
building /gnu/store/36q02kw9bbi0vrgncw5jx8ibwqdkzbhm-rustc-1.49.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/dsl344gpyyn0d9lhrh4jd2lvvf28js90-rust-1.49.0.drv': 1 dependencies couldn't be built
building /gnu/store/96nlaf0vflnzkwnqsy19ax2kjmra01yw-rustc-1.50.0-src.tar.gz.drv...
cannot build derivation `/gnu/store/k46xcizqj8wh7dh9118s27zjfphh8v6l-rust-1.50.0.drv': 1 dependencies couldn't be built
cannot build derivation `/gnu/store/xzr534n5fcl7k2aryvpkvyvvdn7ybcqy-rust-1.51.0.drv': 1 dependencies couldn't be built
guix build: error: build of `/gnu/store/xzr534n5fcl7k2aryvpkvyvvdn7ybcqy-rust-1.51.0.drv' failed
```

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bug#48239: rust-1.19.0 build fails

[Mark H Weaver]

Hi,

Bone Baboon via Bug reports for GNU Guix <bug-guix@gnu.org> writes:
> On a x86_64 computer when I run `guix build --no-substitutes --cores=1
> rust` it fails during the build phase of rust-1.19.0.

Thanks for the report.

> The build log of rust-1.19.0 is attached.

Here are the last few lines of the log:

--8<---------------cut here---------------start------------->8---
(76/77) BUILDING cargo v0.20.0
> /gnu/store/c7w05pkmcpsqbng62wlxsna2zaybl9v5-mrustc-0.9/bin/mrustc src/tools/cargo/src/cargo/lib.rs -o output/cargo-build/libcargo-0_20_0.rlib --crate-name cargo --crate-type rlib -C emit-depfile=output/cargo-build/libcargo-0_20_0.rlib.d --crate-tag 0_20_0 -g --cfg debug_assertions -O -L output -L /gnu/store/c7w05pkmcpsqbng62wlxsna2zaybl9v5-mrustc-0.9/lib/mrust -L output/cargo-build --extern crates_io=output/cargo-build/libcrates_io-0_9_0.rlib --extern crossbeam=output/cargo-build/libcrossbeam-0_2_10.rlib --extern curl=output/cargo-build/libcurl-0_4_6.rlib --extern docopt=output/cargo-build/libdocopt-0_7_0.rlib --extern env_logger=output/cargo-build/libenv_logger-0_4_2.rlib --extern error_chain=output/cargo-build/liberror_chain-0_10_0.rlib --extern filetime=output/cargo-build/libfiletime-0_1_10.rlib --extern flate2=output/cargo-build/libflate2-0_2_19.rlib --extern fs2=output/cargo-build/libfs2-0_4_1.rlib --extern git2=output/cargo-build/libgit2-0_6_6.rlib --extern git2_curl=output/cargo-build/libgit2_curl-0_7_0.rlib --extern glob=output/cargo-build/libglob-0_2_11.rlib --extern jobserver=output/cargo-build/libjobserver-0_1_6.rlib --extern libc=output/cargo-build/liblibc-0_2_22.rlib --extern libgit2_sys=output/cargo-build/liblibgit2_sys-0_6_12.rlib --extern log=output/cargo-build/liblog-0_3_7.rlib --extern num_cpus=output/cargo-build/libnum_cpus-1_4_0.rlib --extern rustc_serialize=output/cargo-build/librustc_serialize-0_3_24.rlib --extern scoped_tls=output/cargo-build/libscoped_tls-0_1_0.rlib --extern semver=output/cargo-build/libsemver-0_7_0.rlib --extern serde=output/cargo-build/libserde-1_0_6.rlib --extern serde_derive=output/cargo-build/libserde_derive-1_0_6-plugin --extern serde_ignored=output/cargo-build/libserde_ignored-0_0_3.rlib --extern serde_json=output/cargo-build/libserde_json-1_0_2.rlib --extern shell_escape=output/cargo-build/libshell_escape-0_1_3.rlib --extern tar=output/cargo-build/libtar-0_4_13.rlib --extern tempdir=output/cargo-build/libtempdir-0_3_5.rlib --extern term=output/cargo-build/libterm-0_4_5.rlib --extern toml=output/cargo-build/libtoml-0_4_1.rlib --extern url=output/cargo-build/liburl-1_4_0.rlib --extern openssl=output/cargo-build/libopenssl-0_9_12.rlib
BUILDING cargo v0.20.0
> /gnu/store/c7w05pkmcpsqbng62wlxsna2zaybl9v5-mrustc-0.9/bin/mrustc src/tools/cargo/src/bin/cargo.rs -o output/cargo-build/cargo --crate-name cargo --crate-type bin -C emit-depfile=output/cargo-build/cargo.d --crate-tag 0_20_0 -g --cfg debug_assertions -O -L output -L /gnu/store/c7w05pkmcpsqbng62wlxsna2zaybl9v5-mrustc-0.9/lib/mrust -L output/cargo-build --extern cargo=output/cargo-build/libcargo-0_20_0.rlib --extern crates_io=output/cargo-build/libcrates_io-0_9_0.rlib --extern crossbeam=output/cargo-build/libcrossbeam-0_2_10.rlib --extern curl=output/cargo-build/libcurl-0_4_6.rlib --extern docopt=output/cargo-build/libdocopt-0_7_0.rlib --extern env_logger=output/cargo-build/libenv_logger-0_4_2.rlib --extern error_chain=output/cargo-build/liberror_chain-0_10_0.rlib --extern filetime=output/cargo-build/libfiletime-0_1_10.rlib --extern flate2=output/cargo-build/libflate2-0_2_19.rlib --extern fs2=output/cargo-build/libfs2-0_4_1.rlib --extern git2=output/cargo-build/libgit2-0_6_6.rlib --extern git2_curl=output/cargo-build/libgit2_curl-0_7_0.rlib --extern glob=output/cargo-build/libglob-0_2_11.rlib --extern jobserver=output/cargo-build/libjobserver-0_1_6.rlib --extern libc=output/cargo-build/liblibc-0_2_22.rlib --extern libgit2_sys=output/cargo-build/liblibgit2_sys-0_6_12.rlib --extern log=output/cargo-build/liblog-0_3_7.rlib --extern num_cpus=output/cargo-build/libnum_cpus-1_4_0.rlib --extern rustc_serialize=output/cargo-build/librustc_serialize-0_3_24.rlib --extern scoped_tls=output/cargo-build/libscoped_tls-0_1_0.rlib --extern semver=output/cargo-build/libsemver-0_7_0.rlib --extern serde=output/cargo-build/libserde-1_0_6.rlib --extern serde_derive=output/cargo-build/libserde_derive-1_0_6-plugin --extern serde_ignored=output/cargo-build/libserde_ignored-0_0_3.rlib --extern serde_json=output/cargo-build/libserde_json-1_0_2.rlib --extern shell_escape=output/cargo-build/libshell_escape-0_1_3.rlib --extern tar=output/cargo-build/libtar-0_4_13.rlib --extern tempdir=output/cargo-build/libtempdir-0_3_5.rlib --extern term=output/cargo-build/libterm-0_4_5.rlib --extern toml=output/cargo-build/libtoml-0_4_1.rlib --extern url=output/cargo-build/liburl-1_4_0.rlib --extern openssl=output/cargo-build/libopenssl-0_9_12.rlib
"libcore"
command "output/rustc-build/rustc" "-C" "linker=/gnu/store/afpgzln8860m6yfhxy6i8n9rywbp85cy-gcc-7.5.0/bin/gcc" "-Z" "force-unstable-if-unmarked" "-L" "output/target-libs" "src/libcore/lib.rs" "-o" "output/target-libs/libcore.rlib" failed with signal 8
--8<---------------cut here---------------end--------------->8---

On x86_64-linux systems, signal 8 is SIGFPE i.e. a floating-point
exception, or "Erroneous arithmetic operation" as the comment says in
include/bits/signum-generic.h.

Are you aware of any relevant customizations to your kernel
configuration that might possibly be related to this?

For what it's worth, on my Thinkpad X200 (Core 2 Duo) with 4 GB of RAM
and 8 GB of swap, I've been successully building Rust locally using Guix
for many years, as long as I don't run other memory intensive processes
at the same time.

It might be worth trying the build a second time.  Occasionally we see
nondeterministic build failures in some packages, although I don't
recall seeing such failures in Rust.

     Regards,
       Mark

-- 
Disinformation flourishes because many people care deeply about
injustice but very few check the facts.  Ask me about
<https://stallmansupport.org>.

bug#48239: rust-1.19.0 build fails

[Bone Baboon via Bug reports for GNU Guix]

Mark H Weaver writes:
> Are you aware of any relevant customizations to your kernel
> configuration that might possibly be related to this?

The system configuration includes:

```
  (kernel-arguments
   (append
    (list
     "nomodeset"
     "ipv6.disable=1")
    %default-kernel-arguments))
```

Without "nomodeset" the computer is not able to boot.

"ipv6.disable=1" is to prevent ipv6 leaks from compromising the privacy
provided by a VPN service I am using.

> For what it's worth, on my Thinkpad X200 (Core 2 Duo) with 4 GB of RAM
> and 8 GB of swap, I've been successully building Rust locally using Guix
> for many years, as long as I don't run other memory intensive processes
> at the same time.

That is good to know.

I was able to build the Rust bootstrap chain from source on this
computer before.  It took several days to complete.

> It might be worth trying the build a second time.  Occasionally we see
> nondeterministic build failures in some packages, although I don't
> recall seeing such failures in Rust.

I tried again and got the same error.

bug#48239: rust-1.19.0 build fails

[Bone Baboon via Bug reports for GNU Guix]

Mark H Weaver writes:
> It might be worth trying the build a second time.

I have tried to build Rust again after doing a pull.  It fails with the
same error.

bug#48239: rust-1.19.0 build fails

[Mark H Weaver]

Hi,

Bone Baboon <bone.baboon@disroot.org> writes:

> Mark H Weaver writes:
>> Are you aware of any relevant customizations to your kernel
>> configuration that might possibly be related to this?
>
> The system configuration includes:
>
> ```
>   (kernel-arguments
>    (append
>     (list
>      "nomodeset"
>      "ipv6.disable=1")
>     %default-kernel-arguments))
> ```

Thanks.  Those don't look relevant to this issue.

>> It might be worth trying the build a second time.  Occasionally we see
>> nondeterministic build failures in some packages, although I don't
>> recall seeing such failures in Rust.
>
> I tried again and got the same error.

Okay.  I think the next step, if you're sufficiently motivated, is to
try to debug this problem yourself.  I'd be glad to help, but
unfortunately I can't do it myself, since I'm unable to reproduce this
problem on my systems.

Here's the basic outline of how to proceed:

(1) First, you'll need the failed build directory in
    /tmp/guix-build-rust-1.19.0.drv-0.  If you've deleted it, recreate
    it by running "guix build rust --keep-failed" and waiting for it to
    fail.  If it has a different name, rename it to have the name above.

(2) Launch a bash shell that you'll use to retry the failed command.  In
    that shell, first run "env -i $(which bash)" to clear most of the
    existing environment variable settings, and then "source
    /tmp/guix-build-rust-1.19.0.drv-0/environment-variables" to load the
    ones that were in use during the build.

(3) Move to the appropriate directory and try re-running the failed
    command (found near the end of the failed build log):

    output/rustc-build/rustc -C \
    linker=/gnu/store/afpgzln8860m6yfhxy6i8n9rywbp85cy-gcc-7.5.0/bin/gcc \
    -Z force-unstable-if-unmarked -L output/target-libs \
    src/libcore/lib.rs -o output/target-libs/libcore.rlib

If you still get SIGFPE, then try running that command again within GDB
and see if you can get a backtrace.  Since GDB won't be in your PATH,
you'll need to launch it via it's absolute file name, which you can get
from another shell using "guix build gdb".

You'll run "/gnu/store/…-gdb-10.1/bin/gdb output/rustc-build/rustc" and
then within GDB: "run -C linker=/gnu/store/…-gcc-7.5.0/bin/gcc …" (the
entire command except for the "output/rustc-build/rustc").

Hopefully the SIGFPE will happen within GDB as well, returning you to
the GDB prompt.  Then type "bt" to get a backtrace, and show it to us.
Some fiddling may be required to get a decent backtrace with full source
information, e.g. by running "dir DIRNAME" within GDB to add a directory
to the "source path" (where it searches for the source files).

Anyway, if we can figure out where the SIGFPE is happening, perhaps we
can find the underlying problem, or at least report it to the mrustc
developers.

      Thanks,
        Mark

-- 
Disinformation flourishes because many people care deeply about injustice
but very few check the facts.  Ask me about <https://stallmansupport.org>.

bug#48239: rust-1.19.0 build fails

[Bone Baboon via Bug reports for GNU Guix]

[-- Attachment #1: Type: text/plain, Size: 2826 bytes --]

Thank you for sharing those debugging instructions.

I have done another pull and now rust is failing to build for a
different reason.

`guix describe` outputs:

```
Generation 24   May 12 2021 18:06:24    (current)
  guix d6aeebb
    repository URL: https://git.savannah.gnu.org/git/guix.git
    branch: master
    commit: d6aeebb23639258311fdfb9dbf5f903079fde51a
```

Now rust 1.19.0 builds successfully but rust 1.20.0 has failing tests.

The build log is attached.

Mark H Weaver writes:

> Okay.  I think the next step, if you're sufficiently motivated, is to
> try to debug this problem yourself.  I'd be glad to help, but
> unfortunately I can't do it myself, since I'm unable to reproduce this
> problem on my systems.
>
> Here's the basic outline of how to proceed:
>
> (1) First, you'll need the failed build directory in
>     /tmp/guix-build-rust-1.19.0.drv-0.  If you've deleted it, recreate
>     it by running "guix build rust --keep-failed" and waiting for it to
>     fail.  If it has a different name, rename it to have the name above.
>
> (2) Launch a bash shell that you'll use to retry the failed command.  In
>     that shell, first run "env -i $(which bash)" to clear most of the
>     existing environment variable settings, and then "source
>     /tmp/guix-build-rust-1.19.0.drv-0/environment-variables" to load the
>     ones that were in use during the build.
>
> (3) Move to the appropriate directory and try re-running the failed
>     command (found near the end of the failed build log):
>
>     output/rustc-build/rustc -C \
>     linker=/gnu/store/afpgzln8860m6yfhxy6i8n9rywbp85cy-gcc-7.5.0/bin/gcc \
>     -Z force-unstable-if-unmarked -L output/target-libs \
>     src/libcore/lib.rs -o output/target-libs/libcore.rlib
>
> If you still get SIGFPE, then try running that command again within GDB
> and see if you can get a backtrace.  Since GDB won't be in your PATH,
> you'll need to launch it via it's absolute file name, which you can get
> from another shell using "guix build gdb".
>
> You'll run "/gnu/store/…-gdb-10.1/bin/gdb output/rustc-build/rustc" and
> then within GDB: "run -C linker=/gnu/store/…-gcc-7.5.0/bin/gcc …" (the
> entire command except for the "output/rustc-build/rustc").
>
> Hopefully the SIGFPE will happen within GDB as well, returning you to
> the GDB prompt.  Then type "bt" to get a backtrace, and show it to us.
> Some fiddling may be required to get a decent backtrace with full source
> information, e.g. by running "dir DIRNAME" within GDB to add a directory
> to the "source path" (where it searches for the source files).
>
> Anyway, if we can figure out where the SIGFPE is happening, perhaps we
> can find the underlying problem, or at least report it to the mrustc
> developers.


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