lib: establish Zircon libc++ and KTL foundation

6 files changed, 99 insertions, 10 deletions

diff --git a/scripts/build/environments/kernel.mk b/scripts/build/environments/kernel.mk
index 088cdf0..1d6c8cf 100644
--- a/scripts/build/environments/kernel.mk
+++ b/scripts/build/environments/kernel.mk
@@ -14,7 +14,7 @@ CFLAGS := $(WARNINGS) $(KERNEL_OPT_FLAGS) \
           $(TOOLCHAIN_CFLAGS) $(KCPPFLAGS) $(INCLUDES) \
           -I$(BUILD)/generated
 
-CFLAGS_LIBC := $(CFLAGS) -std=gnu23 -Iinclude/libc-shim \
+CFLAGS_LIBC := -Iinclude/libc-shim $(CFLAGS) -std=gnu23 \
                -Wno-parentheses -Wno-sign-compare
 
 CXXFLAGS := $(CFLAGS) $(TOOLCHAIN_CXXFLAGS) -std=c++23 \
diff --git a/scripts/build/probe-toolchain.sh b/scripts/build/probe-toolchain.sh
index 2f1f600..218a821 100755
--- a/scripts/build/probe-toolchain.sh
+++ b/scripts/build/probe-toolchain.sh
@@ -10,6 +10,12 @@ family=$5
 target=$6
 gcc_toolchain=$7
 sysroot=$8
+ktl_include=$9
+ktl_after_include=${10}
+libc_include=${11}
+libc_after_include=${12}
+libcxx_include=${13}
+compiler_resource_include=${14}
 
 set --
 if [ "$family" = clang ]; then
@@ -28,6 +34,22 @@ probe() {
         -fsyntax-only - >/dev/null 2>&1
 }
 
+probe_libcxx() {
+    printf '%s\n' \
+        '#include <ktl/array.h>' \
+        '#include <ktl/atomic.h>' \
+        '#include <ktl/optional.h>' \
+        '#include <ktl/span.h>' \
+        '#include <ktl/string_view.h>' \
+        'constexpr ktl::array<int, 2> values{1, 2};' \
+        'static_assert(values[1] == 2);' | \
+        "$cxx" "$@" -std=c++23 -ffreestanding -fno-exceptions -fno-rtti \
+        -nostdinc -I include -I "$ktl_include" -I "$libc_include" \
+        -isystem "$compiler_resource_include" \
+        -isystem "$libcxx_include" -idirafter "$ktl_after_include" \
+        -idirafter "$libc_after_include" -fsyntax-only -x c++ - >/dev/null 2>&1
+}
+
 tmp="$output.tmp.$$"
 mkdir -p "$(dirname "$output")"
 {
@@ -37,6 +59,7 @@ mkdir -p "$(dirname "$output")"
     echo "target=$target"
     printf 'c23='; if probe c gnu23 "$@"; then echo yes; else echo no; fi
     printf 'cxx23='; if probe c++ c++23 "$@"; then echo yes; else echo no; fi
+    printf 'libcxx-headers='; if probe_libcxx "$@"; then echo yes; else echo no; fi
     printf 'fno-pie='; if probe c++ c++23 "$@" -fno-pie; then echo yes; else echo no; fi
     printf 'mcmodel-medany='; if probe c++ c++23 "$@" -mcmodel=medany; then echo yes; else echo no; fi
 } > "$tmp"
@@ -44,5 +67,6 @@ mv -f "$tmp" "$output"
 
 grep -q '^c23=yes$' "$output"
 grep -q '^cxx23=yes$' "$output"
+grep -q '^libcxx-headers=yes$' "$output"
 grep -q '^fno-pie=yes$' "$output"
 grep -q '^mcmodel-medany=yes$' "$output"
diff --git a/scripts/build/probes/libc_headers.c b/scripts/build/probes/libc_headers.c
new file mode 100644
index 0000000..e4bdd20
--- /dev/null
+++ b/scripts/build/probes/libc_headers.c
@@ -0,0 +1,10 @@
+/* SPDX-License-Identifier: GPL-2.0-or-later */
+
+#include <assert.h>
+#include <inttypes.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+_Static_assert(sizeof(uintptr_t) == sizeof(void*), "uintptr_t must hold a pointer");
diff --git a/scripts/build/probes/libc_headers.cc b/scripts/build/probes/libc_headers.cc
new file mode 100644
index 0000000..1085cd3
--- /dev/null
+++ b/scripts/build/probes/libc_headers.cc
@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <assert.h>
+#include <inttypes.h>
+#include <multi-file.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <string-file.h>
+#include <string.h>
+
+static_assert(sizeof(uintptr_t) == sizeof(void*));
diff --git a/scripts/build/probes/libcxx.cc b/scripts/build/probes/libcxx.cc
new file mode 100644
index 0000000..8237151
--- /dev/null
+++ b/scripts/build/probes/libcxx.cc
@@ -0,0 +1,16 @@
+// SPDX-License-Identifier: GPL-2.0-or-later
+
+#include <array>
+#include <atomic>
+#include <optional>
+#include <span>
+#include <string_view>
+#include <type_traits>
+
+constexpr std::array<int, 3> kValues{1, 2, 3};
+static_assert(kValues[2] == 3);
+static_assert(std::is_same_v<std::span<const int>::element_type, const int>);
+static_assert(std::string_view{"libc++"}.size() == 6);
+
+using Optional = std::optional<unsigned long>;
+using Atomic = std::atomic<unsigned long>;
diff --git a/scripts/build/toolchain.mk b/scripts/build/toolchain.mk
index 49d4f0a..d244981 100644
--- a/scripts/build/toolchain.mk
+++ b/scripts/build/toolchain.mk
@@ -10,10 +10,30 @@ LLVM          ?= 0
 LLVM_VERSION  ?= 20
 LD_TYPE       ?= bfd
 LLVM_BINUTILS ?= 0
-CXX_STDLIB    ?= libstdc++
+CXX_STDLIB    ?= libc++
 CXX_ABI       ?= lume
 COMPILER_RUNTIME ?= compiler-default
 
+# One pinned libc++ header snapshot is shared by GCC and Clang.  Platform C
+# declarations and libc++ configuration come from the Zircon libc/KTL layer,
+# not from a Linux or Fuchsia userland __config_site.
+LIBCXX_ROOT ?= third_party/libcxx
+LIBCXX_INCLUDE := $(LIBCXX_ROOT)/include/c++/v1
+KTL_INCLUDE := lib/ktl/include
+KTL_AFTER_INCLUDE := lib/ktl/include-after
+KERNEL_LIBC_INCLUDE := lib/libc/include
+KERNEL_LIBC_AFTER_INCLUDE := lib/libc/include-after
+
+ifeq ($(wildcard $(LIBCXX_INCLUDE)/__config),)
+$(error missing pinned libc++ headers under '$(LIBCXX_INCLUDE)')
+endif
+ifeq ($(wildcard $(KTL_INCLUDE)/__config_site),)
+$(error missing KTL libc++ configuration under '$(KTL_INCLUDE)')
+endif
+ifneq ($(CXX_STDLIB),libc++)
+$(error unsupported CXX_STDLIB '$(CXX_STDLIB)' (LumeOS uses its pinned libc++ headers))
+endif
+
 GCC_TOOLCHAIN ?=
 CROSS_COMPILE ?=
 
@@ -64,29 +84,36 @@ CC  := $(CLANG)
 CXX := $(CLANGXX)
 COMPILER_FAMILY := clang
 TOOLCHAIN_CFLAGS := $(CLANG_TARGET_FLAGS)
-ifeq ($(CXX_STDLIB),libstdc++)
-TOOLCHAIN_CXXFLAGS := -stdlib=libstdc++
-else
-$(error unsupported CXX_STDLIB '$(CXX_STDLIB)' for the current imported runtime)
-endif
+TOOLCHAIN_CXXFLAGS :=
+COMPILER_RESOURCE_DIR := $(strip $(shell $(CXX) $(CLANG_TARGET_FLAGS) -print-resource-dir 2>/dev/null))
+COMPILER_RESOURCE_INCLUDE := $(COMPILER_RESOURCE_DIR)/include
 ifeq ($(LD_TYPE),lld)
 LD := $(LLD)
 LINKER_FAMILY := lld
 else
-ifneq ($(CXX_STDLIB),libstdc++)
-$(error GCC configuration currently requires CXX_STDLIB=libstdc++)
-endif
 LD := $(CROSS_COMPILE)ld
 LINKER_FAMILY := bfd
 endif
+
 else
 CC  := $(CROSS_COMPILE)gcc
 CXX := $(CROSS_COMPILE)g++
 LD  := $(CROSS_COMPILE)ld
 COMPILER_FAMILY := gcc
 LINKER_FAMILY := bfd
+COMPILER_RESOURCE_INCLUDE := $(strip $(shell $(CXX) -print-file-name=include 2>/dev/null))
 endif
 
+ifeq ($(wildcard $(COMPILER_RESOURCE_INCLUDE)/stddef.h),)
+$(error missing compiler resource headers under '$(COMPILER_RESOURCE_INCLUDE)')
+endif
+
+# Kernel and phys code must not observe the Linux target sysroot.  Supply only
+# compiler intrinsic headers explicitly; the target graph provides the kernel
+# libc and KTL layers, followed by the pinned libc++ headers for C++.
+TOOLCHAIN_CFLAGS += -nostdinc -isystem $(COMPILER_RESOURCE_INCLUDE)
+TOOLCHAIN_CXXFLAGS += -isystem $(LIBCXX_INCLUDE)
+
 ifeq ($(LLVM_BINUTILS),1)
 AR      := llvm-ar$(CLANG_SUFFIX)
 NM      := llvm-nm$(CLANG_SUFFIX)