[libc++] Add initial support for picolibc

Picolibc is a C Standard Library that is commonly used in embedded
environments. This patch adds initial support for this configuration
along with pre-commit CI. As of this patch, the test suite only builds
the tests and nothing is run. A follow-up patch will make the test suite
actually run the tests.

Differential Revision: https://reviews.llvm.org/D154246

Author: mplatings

libcxx/cmake/caches/Armv7M-picolibc.cmake

@@ -0,0 +1,38 @@
+set(CMAKE_ASM_COMPILER_TARGET "armv7m-none-eabi" CACHE STRING "")
+set(CMAKE_CXX_COMPILER_TARGET "armv7m-none-eabi" CACHE STRING "")
+set(CMAKE_CXX_FLAGS "-mfloat-abi=soft" CACHE STRING "")
+set(CMAKE_C_COMPILER_TARGET "armv7m-none-eabi" CACHE STRING "")
+set(CMAKE_C_FLAGS "-mfloat-abi=soft" CACHE STRING "")
+set(CMAKE_SYSTEM_NAME Generic CACHE STRING "")
+set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY CACHE STRING "")
+set(COMPILER_RT_BAREMETAL_BUILD ON CACHE BOOL "")
+set(COMPILER_RT_BUILD_LIBFUZZER OFF CACHE BOOL "")
+set(COMPILER_RT_BUILD_PROFILE OFF CACHE BOOL "")
+set(COMPILER_RT_BUILD_SANITIZERS OFF CACHE BOOL "")
+set(COMPILER_RT_BUILD_XRAY OFF CACHE BOOL "")
+set(COMPILER_RT_DEFAULT_TARGET_ONLY ON CACHE BOOL "")
+set(LIBCXXABI_BAREMETAL ON CACHE BOOL "")
+set(LIBCXXABI_ENABLE_ASSERTIONS OFF CACHE BOOL "")
+set(LIBCXXABI_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
+set(LIBCXXABI_ENABLE_SHARED OFF CACHE BOOL "")
+set(LIBCXXABI_ENABLE_STATIC ON CACHE BOOL "")
+set(LIBCXXABI_ENABLE_THREADS OFF CACHE BOOL "")
+set(LIBCXXABI_USE_COMPILER_RT ON CACHE BOOL "")
+set(LIBCXXABI_USE_LLVM_UNWINDER ON CACHE BOOL "")
+set(LIBCXX_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
+set(LIBCXX_ENABLE_FILESYSTEM OFF CACHE STRING "")
+set(LIBCXX_ENABLE_MONOTONIC_CLOCK OFF CACHE BOOL "")
+set(LIBCXX_ENABLE_RANDOM_DEVICE OFF CACHE BOOL "")
+set(LIBCXX_ENABLE_RTTI OFF CACHE BOOL "")
+set(LIBCXX_ENABLE_SHARED OFF CACHE BOOL "")
+set(LIBCXX_ENABLE_STATIC ON CACHE BOOL "")
+set(LIBCXX_ENABLE_THREADS OFF CACHE BOOL "")
+set(LIBCXX_ENABLE_WIDE_CHARACTERS OFF CACHE BOOL "")
+set(LIBCXX_INCLUDE_BENCHMARKS OFF CACHE BOOL "")
+set(LIBCXX_USE_COMPILER_RT ON CACHE BOOL "")
+set(LIBUNWIND_ENABLE_SHARED OFF CACHE BOOL "")
+set(LIBUNWIND_ENABLE_STATIC ON CACHE BOOL "")
+set(LIBUNWIND_ENABLE_THREADS OFF CACHE BOOL "")
+set(LIBUNWIND_IS_BAREMETAL ON CACHE BOOL "")
+set(LIBUNWIND_REMEMBER_HEAP_ALLOC ON CACHE BOOL "")
+set(LIBUNWIND_USE_COMPILER_RT ON CACHE BOOL "")

libcxx/docs/index.rst

@@ -124,16 +124,17 @@ GCC          12              In C++11 or later only     latest stable release pe
 
 Libc++ also supports common platforms and architectures:
 
-=============== ========================= ============================
-Target platform Target architecture       Notes
-=============== ========================= ============================
-macOS 10.13+    i386, x86_64, arm64
-FreeBSD 12+     i386, x86_64, arm
-Linux           i386, x86_64, arm, arm64  Only glibc-2.24 and later and no other libc is officially supported
-Android 5.0+    i386, x86_64, arm, arm64
-Windows         i386, x86_64              Both MSVC and MinGW style environments, ABI in MSVC environments is :doc:`unstable <DesignDocs/ABIVersioning>`
-AIX 7.2TL5+     powerpc, powerpc64
-=============== ========================= ============================
+===================== ========================= ============================
+Target platform       Target architecture       Notes
+===================== ========================= ============================
+macOS 10.13+          i386, x86_64, arm64
+FreeBSD 12+           i386, x86_64, arm
+Linux                 i386, x86_64, arm, arm64  Only glibc-2.24 and later and no other libc is officially supported
+Android 5.0+          i386, x86_64, arm, arm64
+Windows               i386, x86_64              Both MSVC and MinGW style environments, ABI in MSVC environments is :doc:`unstable <DesignDocs/ABIVersioning>`
+AIX 7.2TL5+           powerpc, powerpc64
+Embedded (picolibc)   arm                       Support for building with picolibc is currently work-in-progress
+===================== ========================= ============================
 
 Generally speaking, libc++ should work on any platform that provides a fairly complete
 C Standard Library. It is also possible to turn off parts of the library for use on

libcxx/test/configs/armv7m-picolibc-libc++.cfg.in

@@ -0,0 +1,42 @@
+lit_config.load_config(config, '@CMAKE_CURRENT_BINARY_DIR@/cmake-bridge.cfg')
+
+libc_linker_script = '@CMAKE_INSTALL_PREFIX@/lib/picolibcpp.ld'
+
+config.substitutions.append(('%{flags}', '--sysroot=@CMAKE_INSTALL_PREFIX@'))
+
+config.substitutions.append(('%{compile_flags}',
+    '-nostdinc++ -I %{include} -I %{target-include} -I %{libcxx}/test/support'
+
+    # Disable warnings in cxx_atomic_impl.h:
+    # "large atomic operation may incur significant performance penalty; the
+    # access size (4 bytes) exceeds the max lock-free size (0  bytes)"
+    ' -Wno-atomic-alignment'
+
+    # Various libc++ headers check for the definition of _NEWLIB_VERSION
+    # which for picolibc is defined in picolibc.h.
+    ' -include picolibc.h'
+))
+config.substitutions.append(('%{link_flags}',
+    '-nostdlib -nostdlib++ -L %{lib} -lc++ -lc++abi'
+    ' -lc -lm -lclang_rt.builtins -lsemihost -lcrt0-semihost' +
+    ' -T {}'.format(libc_linker_script) +
+    ' -Wl,--defsym=__flash=0x0'
+    ' -Wl,--defsym=__flash_size=0x400000'
+    ' -Wl,--defsym=__ram=0x21000000'
+    ' -Wl,--defsym=__ram_size=0x1000000'
+    ' -Wl,--defsym=__stack_size=0x1000'
+))
+config.substitutions.append(('%{exec}',
+    'true' # TODO use qemu-system-arm
+))
+config.available_features.add('libcxx-fake-executor')
+
+import os, site
+site.addsitedir(os.path.join('@LIBCXX_SOURCE_DIR@', 'utils'))
+import libcxx.test.params, libcxx.test.config
+libcxx.test.config.configure(
+    libcxx.test.params.DEFAULT_PARAMETERS,
+    libcxx.test.features.DEFAULT_FEATURES,
+    config,
+    lit_config
+)

libcxx/test/libcxx/atomics/atomics.types.generic/atomics.types.float/lockfree.pass.cpp

@@ -8,6 +8,7 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: target={{.+}}-windows-gnu
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 //   static constexpr bool is_always_lock_free = implementation-defined;
 //   bool is_lock_free() const volatile noexcept;

libcxx/test/libcxx/clang_modules_include.gen.py

@@ -39,6 +39,9 @@
 // TODO: Investigate this failure
 // UNSUPPORTED{BLOCKLIT}: LIBCXX-FREEBSD-FIXME
 
+// TODO: Investigate this failure
+// UNSUPPORTED{BLOCKLIT}: LIBCXX-PICOLIBC-FIXME
+
 {lit_header_restrictions.get(header, '')}
 
 #include <{header}>

libcxx/test/libcxx/selftest/dsl/dsl.sh.py

@@ -6,6 +6,8 @@
 #
 # ===----------------------------------------------------------------------===##
 
+# XFAIL: libcxx-fake-executor
+
 # Note: We prepend arguments with 'x' to avoid thinking there are too few
 #       arguments in case an argument is an empty string.
 # RUN: %{python} %s x%S x%T x%{substitutions}

libcxx/test/libcxx/selftest/pass.cpp/run-error.pass.cpp

@@ -6,6 +6,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+// UNSUPPORTED: libcxx-fake-executor
 // XFAIL: *
 
 // Make sure the test DOES NOT pass if it fails at runtime.

libcxx/test/libcxx/selftest/pass.mm/run-error.pass.mm

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 
 // REQUIRES: objective-c++
+// UNSUPPORTED: libcxx-fake-executor
 
 // XFAIL: *
 

libcxx/test/libcxx/system_reserved_names.gen.py

@@ -63,7 +63,8 @@
 #endif
 
 // Test that libc++ doesn't use names that collide with FreeBSD system macros.
-#ifndef __FreeBSD__
+// newlib and picolibc also define these macros
+#if !defined(__FreeBSD__) && !defined(_NEWLIB_VERSION)
 #  define __null_sentinel SYSTEM_RESERVED_NAME
 #  define __generic SYSTEM_RESERVED_NAME
 #endif
@@ -101,7 +102,10 @@
 # define __pre SYSTEM_RESERVED_NAME
 #endif
 
-#define __input SYSTEM_RESERVED_NAME
+// Newlib & picolibc use __input as a parameter name of a64l & l64a
+#ifndef _NEWLIB_VERSION
+# define __input SYSTEM_RESERVED_NAME
+#endif
 #define __output SYSTEM_RESERVED_NAME
 
 #define __acquire SYSTEM_RESERVED_NAME

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/assign.pass.cpp

@@ -8,6 +8,7 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: target={{.+}}-windows-gnu
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 //  floating-point-type operator=(floating-point-type) volatile noexcept;
 //  floating-point-type operator=(floating-point-type) noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/compare_exchange_strong.pass.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 // bool compare_exchange_strong(T& expected, T desired,
 //                            memory_order success, memory_order failure) volatile noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/compare_exchange_weak.pass.cpp

@@ -7,6 +7,7 @@
 //===----------------------------------------------------------------------===//
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 // bool compare_exchange_weak(T& expected, T desired,
 //                            memory_order success, memory_order failure) volatile noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/ctor.pass.cpp

@@ -8,6 +8,7 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: target={{.+}}-windows-gnu
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 // constexpr atomic() noexcept;
 // constexpr atomic(floating-point-type) noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/exchange.pass.cpp

@@ -11,6 +11,7 @@
 // XFAIL: tsan
 // XFAIL: target={{x86_64-.*}} && msan
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 //  T exchange(T, memory_order = memory_order::seq_cst) volatile noexcept;
 //  T exchange(T, memory_order = memory_order::seq_cst) noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/fetch_add.pass.cpp

@@ -13,6 +13,7 @@
 // Hangs with msan.
 // UNSUPPORTED: msan
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 // floating-point-type fetch_add(floating-point-type,
 //                               memory_order = memory_order::seq_cst) volatile noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/fetch_sub.pass.cpp

@@ -13,6 +13,7 @@
 // Hangs with msan.
 // UNSUPPORTED: msan
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 // floating-point-type fetch_sub(floating-point-type,
 //                               memory_order = memory_order::seq_cst) volatile noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/load.pass.cpp

@@ -10,6 +10,7 @@
 // Clang's support for atomic operations on long double is broken. See https://github.com/llvm/llvm-project/issues/72893
 // XFAIL: tsan
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 //  floating-point-type load(memory_order = memory_order::seq_cst) volatile noexcept;
 //  floating-point-type load(memory_order = memory_order::seq_cst) noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/lockfree.pass.cpp

@@ -8,6 +8,7 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: target={{.+}}-windows-gnu
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 //   static constexpr bool is_always_lock_free = implementation-defined;
 //   bool is_lock_free() const volatile noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/notify_all.pass.cpp

@@ -9,6 +9,7 @@
 // XFAIL: availability-synchronization_library-missing
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 //  void notify_all() volatile noexcept;
 //  void notify_all() noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/notify_one.pass.cpp

@@ -9,6 +9,7 @@
 // XFAIL: availability-synchronization_library-missing
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 //  void notify_one() volatile noexcept;
 //  void notify_one() noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/operator.float.pass.cpp

@@ -8,6 +8,7 @@
 // UNSUPPORTED: c++03, c++11, c++14, c++17
 // UNSUPPORTED: target={{.+}}-windows-gnu
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 //  operator floating-point-type() volatile noexcept;
 //  operator floating-point-type() noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/operator.minus_equals.pass.cpp

@@ -9,6 +9,7 @@
 // UNSUPPORTED: target={{.+}}-windows-gnu
 // XFAIL: LIBCXX-AIX-FIXME
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 // Hangs with msan.
 // UNSUPPORTED: msan
 

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/operator.plus_equals.pass.cpp

@@ -9,6 +9,7 @@
 // UNSUPPORTED: target={{.+}}-windows-gnu
 // XFAIL: LIBCXX-AIX-FIXME
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 // Hangs with msan.
 // UNSUPPORTED: msan
 

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/store.pass.cpp

@@ -9,6 +9,7 @@
 // Clang's support for atomic operations on long double is broken. See https://github.com/llvm/llvm-project/issues/72893
 // XFAIL: tsan
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 // void store(floating-point-type, memory_order = memory_order::seq_cst) volatile noexcept;
 // void store(floating-point-type, memory_order = memory_order::seq_cst) noexcept;

libcxx/test/std/atomics/atomics.types.generic/atomics.types.float/wait.pass.cpp

@@ -11,6 +11,7 @@
 // XFAIL: tsan
 // XFAIL: target={{x86_64-.*}} && msan
 // ADDITIONAL_COMPILE_FLAGS(has-latomic): -latomic
+// XFAIL: !has-64-bit-atomics
 
 // void wait(T old, memory_order order = memory_order::seq_cst) const volatile noexcept;
 // void wait(T old, memory_order order = memory_order::seq_cst) const noexcept;

libcxx/test/std/atomics/atomics.types.generic/integral.pass.cpp

@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: !has-64-bit-atomics
+
 // <atomic>
 
 // template <>

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_fetch_add.pass.cpp

@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: !has-64-bit-atomics
+
 // <atomic>
 
 // template<class T>

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_fetch_add_explicit.pass.cpp

@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: !has-64-bit-atomics
+
 // <atomic>
 
 // template<class T>

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_fetch_and.pass.cpp

@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: !has-64-bit-atomics
+
 // <atomic>
 
 // template<class T>

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_fetch_and_explicit.pass.cpp

@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: !has-64-bit-atomics
+
 // <atomic>
 
 // template<class T>

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_fetch_or.pass.cpp

@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: !has-64-bit-atomics
+
 // <atomic>
 
 // template<class T>

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_fetch_or_explicit.pass.cpp

@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: !has-64-bit-atomics
+
 // <atomic>
 
 // template<class T>

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_fetch_sub.pass.cpp

@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: !has-64-bit-atomics
+
 // <atomic>
 
 // template<class T>

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_fetch_sub_explicit.pass.cpp

@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: !has-64-bit-atomics
+
 // <atomic>
 
 // template<class T>

libcxx/test/std/atomics/atomics.types.operations/atomics.types.operations.req/atomic_fetch_xor.pass.cpp

@@ -6,6 +6,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+// XFAIL: !has-64-bit-atomics
+
 // <atomic>
 
 // template<class T>