bastion: add freestanding C++ standard library (libcxx)feature/freestanding-libcxx

Header-only implementation of a C++ standard library subset for the
freestanding kernel, using Clang builtins wherever possible. Provides
19 public headers (~35 internal files): type_traits, utility, memory,
algorithm, functional, concepts, array, string_view, span, optional,
expected, variant, tuple, bit, limits, new, initializer_list, cstdint,
cstddef, and source_location.

Integration changes:
- kernel/Makefile: add -Ilib/libcxx/include to include path
- kernel/lib/string.cpp: add memchr and strncmp (needed by string_view)
- kernel/lib/cxxabi.cpp: guard placement new against <new> header conflict
- kernel/include/kernel/kernel.h: Panic() now uses std::source_location
- kernel/core/kernel.cpp: Panic() implementation updated to match

Builds cleanly on both x86_64 and aarch64 with zero new warnings.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

1 files changed, 85 insertions, 0 deletions

diff --git a/kernel/lib/libcxx/include/__functional/hash.h b/kernel/lib/libcxx/include/__functional/hash.h
new file mode 100644
index 0000000..24b6487
--- /dev/null
+++ b/kernel/lib/libcxx/include/__functional/hash.h
@@ -0,0 +1,85 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the BastionOS freestanding C++ standard library.
+//
+// Basic hash specializations for integral types, pointers, and bool.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBBASTION_FUNCTIONAL_HASH_H
+#define _LIBBASTION_FUNCTIONAL_HASH_H
+
+#include <__config>
+#include <cstddef>
+#include <cstdint>
+
+_LIBBASTION_BEGIN_NAMESPACE_STD
+
+// Primary template — disabled.
+template<class _Tp>
+struct hash;
+
+namespace __detail {
+
+// FNV-1a for types larger than size_t would be overkill in a kernel.
+// Identity hash for integers, cast-to-size_t for pointers.
+inline constexpr size_t __hash_integral(size_t __val) noexcept {
+    // Mix bits for better distribution — based on splitmix64.
+    __val ^= __val >> 30;
+    __val *= 0xbf58476d1ce4e5b9ULL;
+    __val ^= __val >> 27;
+    __val *= 0x94d049bb133111ebULL;
+    __val ^= __val >> 31;
+    return __val;
+}
+
+} // namespace __detail
+
+// Macro for integral type specializations.
+#define _LIBBASTION_HASH_INTEGRAL(_Type)                                    \
+template<>                                                                  \
+struct hash<_Type> {                                                        \
+    _LIBBASTION_NODISCARD size_t operator()(_Type __val) const noexcept {   \
+        return __detail::__hash_integral(static_cast<size_t>(__val));        \
+    }                                                                       \
+};
+
+_LIBBASTION_HASH_INTEGRAL(bool)
+_LIBBASTION_HASH_INTEGRAL(char)
+_LIBBASTION_HASH_INTEGRAL(signed char)
+_LIBBASTION_HASH_INTEGRAL(unsigned char)
+_LIBBASTION_HASH_INTEGRAL(char8_t)
+_LIBBASTION_HASH_INTEGRAL(char16_t)
+_LIBBASTION_HASH_INTEGRAL(char32_t)
+_LIBBASTION_HASH_INTEGRAL(wchar_t)
+_LIBBASTION_HASH_INTEGRAL(short)
+_LIBBASTION_HASH_INTEGRAL(unsigned short)
+_LIBBASTION_HASH_INTEGRAL(int)
+_LIBBASTION_HASH_INTEGRAL(unsigned int)
+_LIBBASTION_HASH_INTEGRAL(long)
+_LIBBASTION_HASH_INTEGRAL(unsigned long)
+_LIBBASTION_HASH_INTEGRAL(long long)
+_LIBBASTION_HASH_INTEGRAL(unsigned long long)
+
+#undef _LIBBASTION_HASH_INTEGRAL
+
+// Pointer specialization
+template<class _Tp>
+struct hash<_Tp*> {
+    _LIBBASTION_NODISCARD size_t operator()(_Tp* __ptr) const noexcept {
+        return __detail::__hash_integral(reinterpret_cast<size_t>(__ptr));
+    }
+};
+
+// nullptr_t
+template<>
+struct hash<nullptr_t> {
+    _LIBBASTION_NODISCARD size_t operator()(nullptr_t) const noexcept {
+        return 0;
+    }
+};
+
+_LIBBASTION_END_NAMESPACE_STD
+
+#endif // _LIBBASTION_FUNCTIONAL_HASH_H