[Reproducible-builds] [Pkg-octave-devel] Trying to fix random_buildpath_by_octave

[Rafael Laboissiere]

* Reiner Herrmann <reineratreiner-h.de> [2015-10-26 22:06]:
>
> [...]
>
> Here is a quick proof that the path is responsible for the differences:
>
>  $ cp test.c tmp-1/ && cd tmp-1 && mkoctfile test.c && md5sum test.o && cd ..
>  8cd4b14fc2bab0efad22f17920d02455  test.o
>  $ cp test.c tmp-1/ && cd tmp-1 && mkoctfile test.c && md5sum test.o && cd ..
>  8cd4b14fc2bab0efad22f17920d02455  test.o
>  $ cp test.c tmp-2/ && cd tmp-2 && mkoctfile test.c && md5sum test.o && cd ..
>  05d17c676f643adef2c15c3899f6a4a3  test.o
>
> -> compiling the same file in the same directory leads to the same 
> result, while compiling in a different path produces a different object 
> file.
>
> I had a short look at it some time ago, and think that it has to be 
> fixed in this file [0]. There it is creating the temporary (random) 
> directories and copying the source into it.
>
> [0]: https://sources.debian.net/src/octave/4.0.0-5/scripts/pkg/private/install.m/?hl=67,70,96#L67

Thanks for your reply, Reiner.

I think that I found the culprit.  The .oct files for octave are built 
using the mkoctfile program, as you pointed out above.  This program uses 
default values for the the environment variables containing flags for the 
to C++ compilation and binary link.  For instance:

  $ mkdir tmp-1
  $ cp /usr/share/doc/liboctave-dev/examples/oregonator.cc tmp-1
  $ (cd tmp-1 ; mkoctfile -v oregonator.cc)
  g++ -c -D_FORTIFY_SOURCE=2 -fPIC -I/usr/include/octave-4.0.0/octave/.. -I/usr/include/octave-4.0.0/octave -I/usr/include/hdf5/serial -I/usr/include/mpi -pthread -fopenmp -mieee-fp -g -O2 -fstack-protector-strong -Wformat -Werror=format-security oregonator.cc -o oregonator.o
  g++ -shared -Wl,-Bsymbolic  -o oregonator.oct  oregonator.o  -L/usr/lib/i386-linux-gnu/octave/4.0.0 -L/usr/lib/i386-linux-gnu -loctinterp -loctave -Wl,-z,relro

I discovered that the "-g" is responsible for the difffrences in the 
resulting binaries.  Here is the proof:

  $ (cd ../tmp-1 ; CXXFLAGS="-g -O2 -fstack-protector-strong -Wformat -Werror=format-security" mkoctfile oregonator.cc ; md5sum oregonator.o*)
  e10495ec145b6c3f946c1728fa64afd2  oregonator.o
  641e6c9a7ee23b38a4452e6337f8a6b5  oregonator.oct
  $ (cd ../tmp-2 ; CXXFLAGS="-g -O2 -fstack-protector-strong -Wformat -Werror=format-security" mkoctfile oregonator.cc ; md5sum oregonator.o*)
  ab176e529b49d9d6860b85c7ed7f228c  oregonator.o
  7e3f711217a357714ec676cdee8a7f56  oregonator.oct
  $ (cd ../tmp-1 ; CXXFLAGS="-O2 -fstack-protector-strong -Wformat -Werror=format-security" mkoctfile oregonator.cc ; md5sum oregonator.o*)
  946afa562517e63a5653ba8f842ed6f2  oregonator.o
  bd0d4be1b541f75dad8de2c736dce1bc  oregonator.oct
  $ (cd ../tmp-2 ; CXXFLAGS="-O2 -fstack-protector-strong -Wformat -Werror=format-security" mkoctfile oregonator.cc ; md5sum oregonator.o*)
  946afa562517e63a5653ba8f842ed6f2  oregonator.o
  bd0d4be1b541f75dad8de2c736dce1bc  oregonator.oct

I just committed a change to the octave-pkg-dev package for removing the 
-g option form the compilation flags [1]. The DOG packages seem to have 
reproducible builds now, at least as regards the binary files *.oct that 
are included in the package.

@DOG: Please, review my changes and, if you think everything is ok, I 
will prepare a new version of octave-pkg-dev.

Rafael

1. http://anonscm.debian.org/cgit/pkg-octave/octave-pkg-dev.git/commit/?id=deed2ea875c0d41b882503e521e83bf0c025aa5f