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, 57 insertions, 0 deletions

diff --git a/kernel/lib/libcxx/include/initializer_list b/kernel/lib/libcxx/include/initializer_list
new file mode 100644
index 0000000..31aff39
--- /dev/null
+++ b/kernel/lib/libcxx/include/initializer_list
@@ -0,0 +1,57 @@
+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the BastionOS freestanding C++ standard library.
+//
+// The compiler generates calls to std::initializer_list's private constructor.
+// The memory layout MUST match what Clang expects.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBBASTION_INITIALIZER_LIST
+#define _LIBBASTION_INITIALIZER_LIST
+
+#include <__config>
+#include <cstddef>
+
+_LIBBASTION_BEGIN_NAMESPACE_STD
+
+template<class _Ep>
+class initializer_list {
+public:
+    using value_type      = _Ep;
+    using reference       = const _Ep&;
+    using const_reference = const _Ep&;
+    using size_type       = size_t;
+    using iterator        = const _Ep*;
+    using const_iterator  = const _Ep*;
+
+    _LIBBASTION_NODISCARD constexpr size_type    size()  const noexcept { return __size_; }
+    _LIBBASTION_NODISCARD constexpr const_iterator begin() const noexcept { return __begin_; }
+    _LIBBASTION_NODISCARD constexpr const_iterator end()   const noexcept { return __begin_ + __size_; }
+
+    constexpr initializer_list() noexcept : __begin_(nullptr), __size_(0) {}
+
+private:
+    // Clang constructs initializer_list with (pointer, size).
+    // This constructor and the field order MUST match the compiler's ABI.
+    constexpr initializer_list(const _Ep* __b, size_t __s) noexcept
+        : __begin_(__b), __size_(__s) {}
+
+    const _Ep* __begin_;
+    size_t     __size_;
+};
+
+template<class _Ep>
+_LIBBASTION_NODISCARD inline constexpr const _Ep* begin(initializer_list<_Ep> __il) noexcept {
+    return __il.begin();
+}
+
+template<class _Ep>
+_LIBBASTION_NODISCARD inline constexpr const _Ep* end(initializer_list<_Ep> __il) noexcept {
+    return __il.end();
+}
+
+_LIBBASTION_END_NAMESPACE_STD
+
+#endif // _LIBBASTION_INITIALIZER_LIST