bpo-41100: ctypes: check _dyld_shared_cache_contains_path in find_library #21241
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Is it necessary to add In PyObjC similar code to find_library assumes that a library is in the shared cache if (a) the library path starts with "/usr/lib" or "/lib" and (b) there is a symbolic link (such as /usr/lib/libSystem.dylib). I'm not too happy about using a private symbol, that tends to be fragile. |
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"I'm not too happy about using a private symbol, that tends to be fragile" I just spoke to dyld engineers, _dyld_shared_cache_contains_path will be made a public API in Mac OS 11 Seed 3 I was thinking we'd add it as a private symbol now, and then update it to including |
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"Is it necessary to add _dyld_shared_cache_contains_path, or is safe to assume libraries in /usr/lib and /lib are in the cache?" I think it is necessary, because if we just assumed any name under /lib was in the cache, then it would think literally anything you ask for is in the cache. find_library("FOO") would return /lib/libFOO.dylib, which is not what we want. |
System libraries in Mac OS 11 may be present only in the shared cache, with the actual mach-o file not present in the corresponding location on the filesystem. ctypes.util.find_library should check the shared cache in order to behave consistently across Mac OS 10.15 and earlier and Mac OS 11.0 and later.
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Modules/_ctypes/callproc.c
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| @@ -64,6 +64,10 @@ | |||
| #include "ctypes_dlfcn.h" | |||
| #endif | |||
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| #ifdef __APPLE__ | |||
| extern bool _dyld_shared_cache_contains_path(const char* path) __attribute__((weak_import)); | |||
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This can be replaced with #include <mach-o/dyld.h> after Seed 3
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Can we please wait for official API here? or at least have another PR to clean this up which we can merge later?
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looks like it got pushed out to seed 4
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It is in Xcode 12 beta 4, only enough with the same name but with documentation in a header file.
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yup, updated the pull request to include mach-o/dyld.h instead of declaring a weak import
... and wait for Python fix in python/cpython#21241
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Thanks for the PR. It has been included in and superseded by GH-22855, |
System libraries in Mac OS 11 may be present only in the shared cache,
with the actual mach-o file not present in the corresponding location
on the filesystem. ctypes.util.find_library should check the
shared cache in order to behave consistently across Mac OS 10.15
and earlier and Mac OS 11.0 and later.
https://bugs.python.org/issue41100