85c7857fe2
Apple clang 16 (clang-1600.0.26.6) defaults objective-c++ to a pre-C++11 dialect, so the raw string literal holding the Metal shader in backend_metal.mm fails to parse: backend_metal.mm:12:29: error: use of undeclared identifier 'R' backend_metal.mm:13:10: fatal error: 'metal_stdlib' file not found Pinning gnu++17 on METALXX fixes 'make glm METAL=1' and 'make metal-test'. Verified on macOS 15 / M4 Max: both targets build and all metal backend tests pass.