There is a bug in clang versions before 3.2 (including the one shipped with Xcode) that makes it give a "conflicting types" compile error when there is a static constexpr function defined outside the class. The way to work around this is either to remove one of the "static" or "constexpr" keywords, or to simply put the definition inline.
See: https://stackoverflow.com/a/17494592/2135754
I would try and upgrade Xcode to version 5 to see if the problem is fixed, but the buildbot still runs OS X Lion (10.7) and the last version of Xcode that works on Lion is 4.6.3, so it seems easier to just apply these workarounds for now.
This renames acquire/release to lock/unlock in order to be compatible with std::lock_guard and std::unique_lock (which will eventually replace the *MutexHolder classes). It will also allow us to typedef MutexImpl to std::mutex later on.
A blank string to FindPythonInterp finds the version
of Python that the system "python" interpreter invokes,
so this means the default is now the system default.
This removes the requirement that it only be included
in a single C++ file per library, by forcing the compiler
to emit the function that references the version symbol
as a weak symbol itself. Now, the linker will not only
tolerate redundant inclusions, it will also coalesce them
together.
To access a WeakPointerTo in a thread-safe way, use something like this:
if (auto ptr = weak_ptr.lock()) {
..use ptr as regular PointerTo
}
The new implementation no longer needs a reference to be stored to all weak pointers on the WeakReferenceList; a mere count of weak pointers is sufficient. Therefore, callbacks theoretically no longer require a WeakPointerTo to be constructed.
The WeakPointerTo class is not actually atomic; it could be made so, but I don't believe it's worth it at this time.
Many thirdparty libraries rely on __file__ being set properly, for example to be able to locate data files, so it is easiest to just set this to something remotely sensible (like the executable path).
This is still not a perfect solution, since eg. the wrong version of a package may still be used if older versions are still in the __whl_cache__ directory. We may want to look into using pip to resolve the package versions, or do something clever such as automatically remove cached wheels if a newer version of the same package was downloaded.
rdb
Donny Lawrence
Sam Edwards
Mitchell Stokes