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Backfill <experimental/memory_resource> for Xcode 16 compatibility - #9
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Xcode 16's libc++ removed <experimental/memory_resource>. std::pmr is only available in the macOS system libc++ from macOS 14, it compiles cleanly against an older deployment target and then fails to load on older systems with a missing std::__1::pmr::memory_resource vtable. This implements memory_resource interface and polymorphic_allocator on macOS. Both are header-only, so nothing uses the system C++ library. memory_resource's destructor is defined inline so the class has no Itanium ABI "key function" - its vtable is emitted into every consuming object file rather than being looked up at load time.
tommaisey
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Sep 21, 2026
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I had hoped to avoid reimplementing this header, but I think macOS's clang/libc++ versions have backed us into a corner. If this works, then I'm ok with it 👍
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Xcode 16's libc++ removed
<experimental/memory_resource>.std::pmris only available in the macOS system libc++ from macOS 14, it compiles cleanly against an older deployment target and then fails to load on older systems with a missingstd::__1::pmr::memory_resourcevtable.This implements
memory_resourceinterface andpolymorphic_allocatoron macOS. Both are header-only, so nothing uses the system C++ library.memory_resource's destructor is defined inline so the class has no Itanium ABI "key function" - its vtable is emitted into every consuming object file rather than being looked up at load time.pmr_shim.h authored by Claude. I've reviewed and all looks reasonable. Unit tests pass on Windows/VS2019 and macOS 15/Xcode 16.4.