[libc++] Instantiate hash function externally

Author: philnik777

libcxx/include/__configuration/availability.h

@@ -78,6 +78,9 @@
 // in all versions of the library are available.
 #if !_LIBCPP_HAS_VENDOR_AVAILABILITY_ANNOTATIONS
 
+#  define _LIBCPP_INTRODUCED_IN_LLVM_21 1
+#  define _LIBCPP_INTRODUCED_IN_LLVM_21_ATTRIBUTE /* nothing */
+
 #  define _LIBCPP_INTRODUCED_IN_LLVM_20 1
 #  define _LIBCPP_INTRODUCED_IN_LLVM_20_ATTRIBUTE /* nothing */
 
@@ -114,6 +117,11 @@
 
 // clang-format off
 
+// LLVM 21
+// TODO: Fill this in
+#  define _LIBCPP_INTRODUCED_IN_LLVM_21 0
+#  define _LIBCPP_INTRODUCED_IN_LLVM_21_ATTRIBUTE __attribute__((unavailable))
+
 // LLVM 20
 // TODO: Fill this in
 #  define _LIBCPP_INTRODUCED_IN_LLVM_20 0
@@ -359,6 +367,9 @@
 #define _LIBCPP_AVAILABILITY_HAS_FROM_CHARS_FLOATING_POINT _LIBCPP_INTRODUCED_IN_LLVM_20
 #define _LIBCPP_AVAILABILITY_FROM_CHARS_FLOATING_POINT _LIBCPP_INTRODUCED_IN_LLVM_20_ATTRIBUTE
 
+#define _LIBCPP_AVAILABILITY_HAS_HASH _LIBCPP_INTRODUCED_IN_LLVM_21
+// No attribute, since we've had hash in the headers before
+
 // Define availability attributes that depend on _LIBCPP_HAS_EXCEPTIONS.
 // Those are defined in terms of the availability attributes above, and
 // should not be vendor-specific.

libcxx/include/__functional/hash.h

@@ -237,6 +237,14 @@ struct __murmur2_or_cityhash<_Size, 64> {
   }
 };
 
+#if _LIBCPP_AVAILABILITY_HAS_HASH
+[[__gnu__::__pure__]] _LIBCPP_EXPORTED_FROM_ABI size_t __hash_memory(_LIBCPP_NOESCAPE const void*, size_t) _NOEXCEPT;
+#else
+_LIBCPP_HIDE_FROM_ABI inline size_t __hash_memory(const void* __ptr, size_t __size) {
+  return __murmur2_or_cityhash<size_t>()(__ptr, __size);
+}
+#endif
+
 template <class _Tp, size_t = sizeof(_Tp) / sizeof(size_t)>
 struct __scalar_hash;
 
@@ -276,7 +284,7 @@ struct __scalar_hash<_Tp, 2> : public __unary_function<_Tp, size_t> {
       } __s;
     } __u;
     __u.__t = __v;
-    return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
+    return std::__hash_memory(&__u, sizeof(__u));
   }
 };
 
@@ -292,7 +300,7 @@ struct __scalar_hash<_Tp, 3> : public __unary_function<_Tp, size_t> {
       } __s;
     } __u;
     __u.__t = __v;
-    return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
+    return std::__hash_memory(&__u, sizeof(__u));
   }
 };
 
@@ -309,7 +317,7 @@ struct __scalar_hash<_Tp, 4> : public __unary_function<_Tp, size_t> {
       } __s;
     } __u;
     __u.__t = __v;
-    return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
+    return std::__hash_memory(&__u, sizeof(__u));
   }
 };
 
@@ -332,7 +340,7 @@ struct _LIBCPP_TEMPLATE_VIS hash<_Tp*> : public __unary_function<_Tp*, size_t> {
       size_t __a;
     } __u;
     __u.__t = __v;
-    return __murmur2_or_cityhash<size_t>()(&__u, sizeof(__u));
+    return std::__hash_memory(&__u, sizeof(__u));
   }
 };
 

libcxx/include/__string/char_traits.h

@@ -534,7 +534,7 @@ __str_find_last_not_of(const _CharT* __p, _SizeT __sz, _CharT __c, _SizeT __pos)
 template <class _Ptr>
 inline _LIBCPP_HIDE_FROM_ABI size_t __do_string_hash(_Ptr __p, _Ptr __e) {
   typedef typename iterator_traits<_Ptr>::value_type value_type;
-  return __murmur2_or_cityhash<size_t>()(__p, (__e - __p) * sizeof(value_type));
+  return std::__hash_memory(__p, (__e - __p) * sizeof(value_type));
 }
 
 _LIBCPP_END_NAMESPACE_STD

libcxx/src/functional.cpp

@@ -16,4 +16,8 @@ bad_function_call::~bad_function_call() noexcept {}
 const char* bad_function_call::what() const noexcept { return "std::bad_function_call"; }
 #endif
 
+size_t __hash_memory(_LIBCPP_NOESCAPE const void* ptr, size_t size) _NOEXCEPT {
+  return __murmur2_or_cityhash<size_t>()(ptr, size);
+}
+
 _LIBCPP_END_NAMESPACE_STD