[Bug 1883531] [NEW] build hangs for 2 hours with -03, yet succeeds with -O2 very quickly

[Dimitri John Ledkov]

Public bug reported:

blobandconquer package fails to build from source, when building with
-O3 on ppc64el.

It succeeds, if built with -O2.

mastermind.o is the offending object.

Get the source:

   pull-lp-source blobandconquer
   cd blobandconquer-*
   sudo apt build-dep ./

If you don't have pull-lp-source, you can download the tarball directly
and install build-depends elsehow:

   wget 'https://launchpad.net/ubuntu/+archive/primary/+sourcefiles/blobandconquer/1.11-dfsg+20-1.1ubuntu1/blobandconquer_1.11-dfsg+20.orig.tar.gz'
   tar xvf blobandconquer*.tar.gz
   cd blobandconquer-*
   sudo apt build-dep blobandconquer

inside there:

$ CXXFLAGS=-O3 make mastermind.o
g++ -O3 -Wformat=2 -Wformat-security -Wstrict-aliasing=2 -Wmissing-format-attribute -Wmissing-noreturn -Wdisabled-optimization `sdl-config --cflags` -DVERSION=1.11 -DRELEASE=0 -DUSEPAK=0 -DDEV=0 -DPAKNAME=\"blobAndConquer.pak\" -DPAKLOCATION=\"/usr/share/games/blobAndConquer/\" -DGAMEPLAYMANUAL=\"/usr/share/doc/blobAndConquer//index.html\" -Wall -DLOCALEDIR=\"/usr/share/locale/\" -g  -c src/puzzles/mastermind.cpp
^Cmake: *** [makefile:100: mastermind.o] Interrupt

hangs.

Where as with -O2 it builds very quickly:

$ CXXFLAGS=-O2 make mastermind.o
g++ -O2 -Wformat=2 -Wformat-security -Wstrict-aliasing=2 -Wmissing-format-attribute -Wmissing-noreturn -Wdisabled-optimization `sdl-config --cflags` -DVERSION=1.11 -DRELEASE=0 -DUSEPAK=0 -DDEV=0 -DPAKNAME=\"blobAndConquer.pak\" -DPAKLOCATION=\"/usr/share/games/blobAndConquer/\" -DGAMEPLAYMANUAL=\"/usr/share/doc/blobAndConquer//index.html\" -Wall -DLOCALEDIR=\"/usr/share/locale/\" -g  -c src/puzzles/mastermind.cpp

On our builders it hangs for 150 minutes without producing any output,
which is our current timeout for builders.

The code in blobandconquer might be buggy, improvements to make it build
with -O3 are welcome. But also, toolchain should not hang indefinitely.

Ubuntu defaults to -O3 for ppc64el port otherwise.

** Affects: ubuntu-power-systems
     Importance: Undecided
     Assignee: bugproxy (bugproxy)
         Status: New

** Affects: gcc-9 (Ubuntu)
     Importance: Undecided
         Status: New


** Tags: ppc64el reverse-proxy-bugzilla

** Also affects: ubuntu-power-systems
   Importance: Undecided
       Status: New

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https://bugs.launchpad.net/bugs/1883531

Title:
  build hangs for 2 hours with -03, yet succeeds with -O2 very quickly

Status in The Ubuntu-power-systems project:
  New
Status in gcc-9 package in Ubuntu:
  New

Bug description:
  blobandconquer package fails to build from source, when building with
  -O3 on ppc64el.

  It succeeds, if built with -O2.

  mastermind.o is the offending object.

  Get the source:

     pull-lp-source blobandconquer
     cd blobandconquer-*
     sudo apt build-dep ./

  If you don't have pull-lp-source, you can download the tarball
  directly and install build-depends elsehow:

     wget 'https://launchpad.net/ubuntu/+archive/primary/+sourcefiles/blobandconquer/1.11-dfsg+20-1.1ubuntu1/blobandconquer_1.11-dfsg+20.orig.tar.gz'
     tar xvf blobandconquer*.tar.gz
     cd blobandconquer-*
     sudo apt build-dep blobandconquer

  inside there:

  $ CXXFLAGS=-O3 make mastermind.o
  g++ -O3 -Wformat=2 -Wformat-security -Wstrict-aliasing=2 -Wmissing-format-attribute -Wmissing-noreturn -Wdisabled-optimization `sdl-config --cflags` -DVERSION=1.11 -DRELEASE=0 -DUSEPAK=0 -DDEV=0 -DPAKNAME=\"blobAndConquer.pak\" -DPAKLOCATION=\"/usr/share/games/blobAndConquer/\" -DGAMEPLAYMANUAL=\"/usr/share/doc/blobAndConquer//index.html\" -Wall -DLOCALEDIR=\"/usr/share/locale/\" -g  -c src/puzzles/mastermind.cpp
  ^Cmake: *** [makefile:100: mastermind.o] Interrupt

  hangs.

  Where as with -O2 it builds very quickly:

  $ CXXFLAGS=-O2 make mastermind.o
  g++ -O2 -Wformat=2 -Wformat-security -Wstrict-aliasing=2 -Wmissing-format-attribute -Wmissing-noreturn -Wdisabled-optimization `sdl-config --cflags` -DVERSION=1.11 -DRELEASE=0 -DUSEPAK=0 -DDEV=0 -DPAKNAME=\"blobAndConquer.pak\" -DPAKLOCATION=\"/usr/share/games/blobAndConquer/\" -DGAMEPLAYMANUAL=\"/usr/share/doc/blobAndConquer//index.html\" -Wall -DLOCALEDIR=\"/usr/share/locale/\" -g  -c src/puzzles/mastermind.cpp

  On our builders it hangs for 150 minutes without producing any output,
  which is our current timeout for builders.

  The code in blobandconquer might be buggy, improvements to make it
  build with -O3 are welcome. But also, toolchain should not hang
  indefinitely.

  Ubuntu defaults to -O3 for ppc64el port otherwise.

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