[issue9998] ctypes find_library should search LD_LIBRARY_PATH on linux

[Martin Panter]

Martin Panter added the comment:

Thanks Pau, for some reason I didn’t pick up the dylib OS X problem last time I looked at that link. This is a quick summary of the library names searched on different platforms:

Windows: {name} and {name}.dll, via %PATH%
OS X: lib{name}.dylib, {name}.dylib and {name}.framework/{name}, via dyld_find()
BSD: lib{name}.* via ldconfig (choose highest ABI version) and cc
Solaris: lib{name}.so via crle, and lib{name}.* via cc
Gnu: lib{name}.* via ldconfig and cc

Already, these cases seem to be half emulating the run-time linker and half the build-time linker. I don’t have a good answer about which is “better” (it would depend on the use case). But since we already have a mix, maybe changing towards run-time would not be such a problem as I first thought.

A half-cooked idea of mine is a simpler function that just accounts for common library naming conventions on various platforms, but does not extract sonames or spawn compilers. I think this could work with what seems to be a common use case of passing the result directly to CDLL(), which will do the real search. For the Windows and OS X cases, a loop might be required to attempt CDLL() with the different possibilities.

But I agree this is straying from the topic of this bug report. Perhaps I should accept that people want to find libraries by just the build-time name, but that are accessible at runtime.

More related reports about find_library() vs CDLL():
Issue 19317: Search Python’s RPATH
Issue 21622: Work without DT_SONAME

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