[Debian-med-packaging] Bug#799107: ismrmrd: library transition needed with GCC 5 as default

[Julien Cristau]

Source: ismrmrd
Version: 1.2.3-2
Severity: important
Tags: sid stretch
User: debian-gcc at lists.debian.org
Usertags: libstdc++-cxx11

Hi,

your library exposes std::string or std::list in its public API, and
therefore breaks ABI on rebuild with g++ 5.  However as the library has
no reverse depends in Debian it's up to you whether to rename the binary
package or not.

Cheers,
Julien

The following is a form letter:

Background [1]: libstdc++6 introduces a new ABI to conform to the
C++11 standard, but keeps the old ABI to not break existing binaries.
Packages which are built with g++-5 are using the new ABI.  Libraries built
from this source package export some of the new __cxx11 or B5cxx11 symbols, and
dropping other symbols.  If these symbols are part of the API of the library,
then this rebuild with g++-5 will trigger a transition for the library.

What is needed:

 - Rebuild the library using g++/g++-5. Note that most likely all C++
   libraries within the build dependencies need a rebuild too. You can
   find the log for a rebuild in
     https://people.debian.org/~doko/logs/gcc5-20150813/
   Search for "BEGIN GCC CXX11" in the log.

 - Decide if the symbols matching __cxx11 or B5cxx11 are part of the
   library API, and are used by the reverse dependencies of the
   library.

 - If there are no symbols matching __cxx11 or B5cxx11 in the symbols
   forming the library API, you should close this issue with a short
   explanation.
 
 - If there are no reverse dependencies, it should be the package
   maintainers decision if a transition is needed.  However this might
   break software which is not in the Debian archive, and built
   against these packages.

 - If a library transition is needed, please prepare for the change.
   Rename the library package, append "v5" to the name of the package
   (e.g. libfoo2 -> libfoo2v5). Such a change can be avoided, if you
   have a soversion bump and you upload this version instead of the
   renamed package.  Prepare a patch and attach it to this issue (mark
   this issue with patch), so that it is possible to NMU such a
   package. We'll probably have more than hundred transitions
   triggered.
   
 - If unsure if a transition is needed, please tag the issue with help
   to ask for feedback from other Debian developers.

The libstdc++6 transition will be a large one, and it will come with a
lot of pain.  Please help it by preparing the follow-up transitions.

[1] https://wiki.debian.org/GCC5#libstdc.2B-.2B-_ABI_transition

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