Linux and C++ ABI, Part 1

One particularly annoying gem about developing on Linux is the general disregard for cross-distribution binary compatibility. There are two big reasons for this, one philosophical and the other is semi-technical:

  • Philosophical: There is a tendency to believe that almost everything on Linux is (or should be) open source; instead of vendors distributing binaries, they should distribute source code for users to compile.
  • Technical: Linux Distribution vendors can theoretically call or place libraries whatever or wherever they want, or compile them with any options they feel necessary, or leave options out which they feel are unnecessary.

Projects which distribute cross-distro binaries (whether open source or not) have to fight an uphill battle on both of these counts. But it only gets worse when dealing with the GNU Standard C++ Library. The huge problem with libstdc++ is that the compiler offers no easy way to either exclude it or to link it statically.

Excluding libstdc++ is possible if you invoke the compiler with gcc instead of g++ — but you need to overload new, new[], delete, and delete[] (simple malloc() wrappers will do). If you use try/catch/throw or dynamic_cast, forget it. You have to link to libstdc++ no matter what.

Static linking is out of the question for DSOs. You can run into all sorts of problems when loading other dynamic libraries or another libstdc++ in the same process. Not only that, but static linking can be nearly impossible.

It gets worse when you realize that the ABI version to libstdc++ tends to get bumped quite often. AMX Mod X experienced compatibility bumps from GCC versions 2.95, 3.0-3.3, and 3.4. As each distribution decides to package different libstdc++ versions/builds, and some distributions are too old to even support the compiler we choose to use, it becomes increasingly difficult to distribute Linux binaries. Asking average users to compile from source is out of the question — many falter on even a graphical installer.

The continual problems with Linux distributions and libstdc++ are well-known and documented by now. This was just your introduction. Next week I will share an extremely frustrating and subtle ABI problem I ran into with libstdc++ and glibc.

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