Bug#870049: diffoscope: hangs on some LLVM bytecode files and maybe other files

[Ximin Luo]

Package: diffoscope
Version: 84
Severity: important

Dear Maintainer,

When testing rustc reproducibility:

$ for i in {1..10}; do diffoscope core-fcc113aeec9d4b78.0.bytecode.0 core-fcc113aeec9d4b78.0.bytecode.1 | wc -l; done
# hangs first time

$ for i in {1..10}; do diffoscope --max-diff-input-lines 0 core-fcc113aeec9d4b78.0.bytecode.0 core-fcc113aeec9d4b78.0.bytecode.1 | wc -l; done
# hangs after a few (3-30) tries, seems random

$ for i in {1..10}; do diff -ru <(llvm-bcanalyzer -dump core-fcc113aeec9d4b78.0.bytecode.0) <(llvm-bcanalyzer -dump core-fcc113aeec9d4b78.0.bytecode.1) | wc -l; done
# succeeds every time

When running `pstree -alup` one can see either one or both llvm-bcanalyzer processes running. I guess there's a race condition to do with filtering command output.

X

-- System Information:
Debian Release: buster/sid
  APT prefers testing
  APT policy: (990, 'testing'), (500, 'unstable-debug'), (500, 'testing-debug'), (500, 'buildd-unstable'), (300, 'unstable'), (100, 'experimental'), (1, 'experimental-debug')
Architecture: amd64 (x86_64)
Foreign Architectures: i386

Kernel: Linux 4.11.0-1-amd64 (SMP w/4 CPU cores)
Locale: LANG=en_GB.utf8, LC_CTYPE=en_GB.utf8 (charmap=UTF-8), LANGUAGE=en_GB:en (charmap=UTF-8)
Shell: /bin/sh linked to /bin/dash
Init: systemd (via /run/systemd/system)

Versions of packages diffoscope depends on:
ii  python3                3.5.3-3
ii  python3-libarchive-c   2.1-3.1
ii  python3-magic          1:5.30-1
ii  python3-pkg-resources  36.0.1-1

Versions of packages diffoscope recommends:
ii  acl                              2.2.52-3+b1
ii  apktool                          2.2.3+dfsg-1
ii  binutils-multiarch               2.28-6
ii  bzip2                            1.0.6-8.1
ii  caca-utils                       0.99.beta19-2+b2
ii  colord                           1.3.3-2
ii  default-jdk [java-sdk]           2:1.8-59
ii  default-jdk-headless             2:1.8-59
ii  device-tree-compiler             1.4.2-1
ii  docx2txt                         1.4-0.2
ii  enjarify                         1:1.0.3-3
ii  fontforge-extras                 0.3-4
ii  fp-utils-3.0.2 [fp-utils]        3.0.2+dfsg-4
ii  genisoimage                      9:1.1.11-3+b2
ii  gettext                          0.19.8.1-2+b1
ii  ghc                              8.0.1-17+b1
ii  ghostscript                      9.21~dfsg-1
ii  giflib-tools                     5.1.4-0.4
ii  gnupg                            2.1.18-8
ii  imagemagick                      8:6.9.7.4+dfsg-12
ii  imagemagick-6.q16 [imagemagick]  8:6.9.7.4+dfsg-12
ii  jsbeautifier                     1.6.4-6
ii  libarchive-tools                 3.2.2-2
ii  llvm                             1:3.8-36
ii  mono-utils                       4.6.2.7+dfsg-1
ii  odt2txt                          0.5-1+b2
ii  oggvideotools                    0.9.1-4
ii  openjdk-8-jdk [java-sdk]         8u131-b11-2
ii  openssh-client                   1:7.5p1-5
ii  pdftk                            2.02-4+b2
ii  pgpdump                          0.31-0.2
ii  poppler-utils                    0.48.0-2
ii  python3-argcomplete              1.8.1-1
ii  python3-debian                   0.1.30
ii  python3-guestfs                  1:1.34.6-2+b1
ii  python3-progressbar              2.3-4
ii  python3-rpm                      4.12.0.2+dfsg1-2+b1
ii  python3-tlsh                     3.4.4+20151206-1+b3
ii  r-base-core                      3.3.3-1
ii  rpm2cpio                         4.12.0.2+dfsg1-2+b1
ii  sng                              1.1.0-1+b1
ii  sqlite3                          3.19.3-3
ii  squashfs-tools                   1:4.3-4
ii  tcpdump                          4.9.0-3
ii  unzip                            6.0-21
ii  vim-common                       2:8.0.0197-5
ii  xxd                              2:8.0.0197-5
ii  xz-utils                         5.2.2-1.3

Versions of packages diffoscope suggests:
ii  libjs-jquery  3.1.1-2

-- no debconf information