[libc] Add a library of standalone C++ utilities.

[sivachandra]

Summary

Some of the existing utils in utils/UnitTest/Test.h have been moved to this new library.

[abrachet]

libc/utils/CPP/Array.h

23–29

I know you aren't looking for comments, but just a quick one. std::array has no private members or constructors which makes it an aggregate, which gives it the super nice constexpr brace initializer syntax. This constructor would anyway need a reference to a preexisting array and couldn't be initialized like Array<...> a({1, 2, 3, 4}); If you make Data public (and remove Length because we can just use N) and remove these 2 constructors then it can be initialized like Array<int, 5> arr {1, 2, 3, 4, 5};

[gchatelet]

Thx @sivachandra

libc/cmake/modules/LLVMLibCRules.cmake

379

Thx!

libc/utils/CPP/Array.h

17

You can use N everywhere, you don't need Length

23–29

+1

libc/utils/CPP/ArrayRef.h

60

That would be nice to have size_t available separately.

80

[nit] It might be easier to start from MutableArrayRef as a base type and inherit from it to constrain constness?

libc/utils/UnitTest/Test.h

68

Can we have an explicit specialization that handles comparing two bool?

[abrachet]

libc/utils/UnitTest/Test.h

21

Now that I see it again, I think this should say "return bool" or "return _Bool"

68

https://reviews.llvm.org/D73472#inline-667032 and line 20 of this file.

[sivachandra]

Address comments. Ready for a code review.

[sivachandra]

libc/utils/CPP/ArrayRef.h

80

Thinking about ArrayRef and MutableArrayRef twists my mind. But, I am only imitating the LLVM arrangement for consistency. Consistency is probably good to avoid surprising ourselves when switching between different pieces of code.

libc/utils/UnitTest/Test.h

21

Fixed this and other typos I found.

68

I do not want an integral type to be implicitly converted to bool. So, what do you think about supporting [ASSERT|EXPECT]_[TRUE|FALSE] via functions like this:

// For [ASSERT|EXPECT]_TRUE.
template <
      typename ValType,
      cpp::EnableIfType<cpp::IsBoolType<ValType>::Value, ValType> = true>
static bool testTrue(RunContext &Ctx, ValType Val, const char *ValStr,
                                  const char *File, unsigned long Line) {
  return Val;
}

// For [ASSERT|EXPECT]_FALSE.
template <
      typename ValType,
      cpp::EnableIfType<cpp::IsBoolType<ValType>::Value, ValType> = true>
static bool testFalse(RunContext &Ctx, ValType Val, const char *ValStr,
                                  const char *File, unsigned long Line) {
  return !Val;
}

Use of cpp::IsBoolType ensures that these functions are restricted to boolean values only.

[miscco]

Comment about empty arrays

libc/utils/CPP/Array.h

37

This is not needed, as the expression T Data[0] is ill formed see C11 standard

Consequently, this should rather be replaced by a static_assert that N != 0

[miscco]

libc/utils/CPP/ArrayRef.h

66

All constructors defere to those of the base class so you should be able to use inheriting constructors aka:
using ArrayRef<T>::ArrayRef<T>;

[gchatelet]

+1 to @miscco 's comments
Other than that LGTM

libc/utils/CPP/ArrayRef.h

80

SGTM

[abrachet]

libc/utils/CPP/Array.h

15–16

We could make this a struct?

libc/utils/CPP/ArrayRef.h

38

Do we want this to be explicit? I think ArrayRef<T> arr = someT; is a little surprising.

75–79

These are constructed from pointers to const T so arguably these constructors should not be allowed.

87

Unnecessary this->

[sivachandra]

libc/utils/CPP/ArrayRef.h

66

It was my mistake that I made them the same. They are not the same as the args are not const qualified in case of MutableArrayRef. See @abrachet's comment below.

87

Strange, but this stackoverflow entry is the most accessible explanation I could find: https://stackoverflow.com/questions/19128796/why-can-i-call-base-template-class-method-from-derived-class

libc/CMakeLists.txt

 cmake_minimum_required(VERSION 3.4.3)
 
+# Use old version of target_sources command which converts the source
+# file paths to full paths.
+cmake_policy(SET CMP0076 OLD)
 list(APPEND CMAKE_MODULE_PATH  "${CMAKE_CURRENT_SOURCE_DIR}/cmake/modules")
 
 # The top-level source directory of libc.
 set(LIBC_SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR})
 # The top-level directory in which libc is being built.
 set(LIBC_BUILD_DIR ${CMAKE_CURRENT_BINARY_DIR})
 
 # Path libc/scripts directory.

libc/cmake/modules/LLVMLibCRules.cmake

if(LIBC_UNITTEST_SUITE)
     )
   endif()
 endfunction(add_libc_unittest)
 
 function(add_libc_testsuite suite_name)
   add_custom_target(${suite_name})
   add_dependencies(check-libc ${suite_name})
 endfunction(add_libc_testsuite)
+
+function(add_header_library target_name)
+  cmake_parse_arguments(
+    "ADD_HEADER_LIB"
+    "" # No optional arguments
+    "" # Single value arguments
+    "HDRS;DEPENDS" # Multi-value arguments
+    ${ARGN}
+  )
+
+  set(FULL_HDR_PATHS "")
+  # TODO: Remove this foreach block when we can switch to the new
+  # version of the CMake policy CMP0076.
+  foreach(hdr IN LISTS ADD_HEADER_LIB_HDRS)
+    list(APPEND FULL_HDR_PATHS ${CMAKE_CURRENT_SOURCE_DIR}/${hdr})
+  endforeach()
+
+  add_library(${target_name} INTERFACE)
+  target_sources(${target_name} INTERFACE ${FULL_HDR_PATHS})
+  if(ADD_HEADER_DEPENDS)
+    add_dependencies(${target_name} ${ADD_HEADER_DEPENDS})
+  endif()
+endfunction(add_header_library)

libc/utils/CMakeLists.txt

+add_subdirectory(CPP)
 add_subdirectory(HdrGen)
 add_subdirectory(UnitTest)
 add_subdirectory(benchmarks)

libc/utils/CPP/Array.h

+//===--------- A self contained equivalent of std::array --------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <stddef.h> // For size_t.
+
+namespace llvm_libc {
+namespace cpp {
+
+template <class T, size_t N> class Array {
+private:
+  T Data[N];
+  size_t Length = N;
+
+public:
+  using iterator = T *;
+  using const_iterator = const T *;
+
+  Array() = default;
+
+  Array(const T (&Arr)[N]) {
+    for (size_t i = 0; i < N; ++i) {
+      Data[i] = Arr[i];
+    }
+  }
+
+  constexpr T *data() { return Data; }
+  constexpr const T *data() const { return Data; }
+
+  constexpr T &front() { return Data[0]; }
+  constexpr T &front() const { return Data[0]; }
+
+  constexpr T &back() { return Data[N - 1]; }
+  constexpr T &back() const { return Data[N - 1]; }
+
+  constexpr T &operator[](size_t Index) { return Data[Index]; }
+
+  constexpr const T &operator[](size_t Index) const { return Data[Index]; }
+
+  constexpr size_t size() const { return Length; }
+
+  constexpr bool empty() const { return Length == 0; }
+
+  constexpr iterator begin() { return Data; }
+  constexpr const_iterator begin() const { return Data; }
+
+  constexpr iterator end() { return Data + N; }
+  const_iterator end() const { return Data + N; }
+};
+
+} // namespace cpp
+} // namespace llvm_libc

libc/utils/CPP/ArrayRef.h

+//===----------------- Self contained ArrayRef type -------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include <stddef.h> // For size_t.
+
+namespace llvm_libc {
+namespace cpp {
+
+// The implementations of ArrayRef and MutualArrayRef in this file are based
+// on the implementations of the types with the same names in
+// llvm/ADT/ArrayRef.h. The implementations in this file are of a limited
+// functionality, but can be extended in an as needed basis.
+
+template <typename T> class ArrayRef {
+public:
+  using iterator = const T *;
+  using const_iterator = const T *;
+
+private:
+  const T *Data = nullptr;
+  size_t Length = 0;
+
+public:
+  ArrayRef() = default;
+
+  // Construct an ArrayRef from a single element.
+  ArrayRef(const T &OneElt) : Data(&OneElt), Length(1) {}
+
+  // Construct an ArrayRef from a pointer and length.
+  ArrayRef(const T *data, size_t length) : Data(data), Length(length) {}
+
+  // Construct an ArrayRef from a range.
+  ArrayRef(const T *begin, const T *end) : Data(begin), Length(end - begin) {}
+
+  // Construct an ArrayRef from a C array.
+  template <size_t N>
+  constexpr ArrayRef(const T (&Arr)[N]) : Data(Arr), Length(N) {}
+
+  iterator begin() const { return Data; }
+  iterator end() const { return Data + Length; }
+
+  bool empty() const { return Length == 0; }
+
+  const T *data() const { return Data; }
+
+  size_t size() const { return Length; }
+
+  const T &operator[](size_t Index) const { return Data[Index]; }
+};
+
+template <typename T> class MutableArrayRef : public ArrayRef<T> {
+public:
+  using iterator = T *;
+#ifdef __size_t__
+  using size_t = __size_t__;
+#else
+  using size_t = unsigned long long;
+#endif // __size_t__
+
+  MutableArrayRef() = default;
+
+  // Construct an ArrayRef from a single element.
+  MutableArrayRef(const T &OneElt) : ArrayRef<T>(OneElt) {}
+
+  // Construct an ArrayRef from a pointer and length.
+  MutableArrayRef(const T *data, size_t length) : ArrayRef<T>(data, length) {}
+
+  // Construct an ArrayRef from a range.
+  MutableArrayRef(const T *begin, const T *end) : ArrayRef<T>(begin, end) {}
+
+  // Construct an ArrayRef from a C array.
+  template <size_t N>
+  constexpr MutableArrayRef(const T (&Arr)[N]) : ArrayRef<T>(Arr) {}
+
+  T *data() const { return const_cast<T *>(ArrayRef<T>::data()); }
+
+  iterator begin() const { return data(); }
+  iterator end() const { return data() + this->size(); }
+
+  T &operator[](size_t Index) const { return data()[Index]; }
+};
+
+} // namespace cpp
+} // namespace llvm_libc

libc/utils/CPP/CMakeLists.txt

+add_header_library(
+  standalone_cpp
+  HDRS
+    Array.h
+    ArrayRef.h
+    TypeTraits.h
+)

libc/utils/CPP/README.md

+This directory contains re-implementations of some C++ standard library as well
+as some LLVM utilities. These are to be used with internal LLVM libc code and
+tests. More utilities will be added on an as needed basis. There are certain
+rules to be followed for future changes and additions:
+
+1. Only two kind of headers can be included: Other headers from this directory,
+and free standing C headers.
+2. Free standing C headers are to be included as C headers and not as C++
+headers. That is, use `#include <stddef.h>` and not `#include <cstddef>`.

libc/utils/CPP/TypeTraits.h

+//===----------------- Self contained C++ type traits -----------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+namespace llvm_libc {
+namespace cpp {
+
+template <bool B, typename T> struct EnableIf;
+template <typename T> struct EnableIf<true, T> { typedef T Type; };
+
+template <bool B, typename T>
+using EnableIfType = typename EnableIf<B, T>::Type;
+
+struct TrueValue {
+  static constexpr bool Value = true;
+};
+
+struct FalseValue {
+  static constexpr bool Value = false;
+};
+
+template <typename Type> struct IsIntegral : public FalseValue {};
+template <> struct IsIntegral<char> : public TrueValue {};
+template <> struct IsIntegral<signed char> : public TrueValue {};
+template <> struct IsIntegral<unsigned char> : public TrueValue {};
+template <> struct IsIntegral<short> : public TrueValue {};
+template <> struct IsIntegral<unsigned short> : public TrueValue {};
+template <> struct IsIntegral<int> : public TrueValue {};
+template <> struct IsIntegral<unsigned int> : public TrueValue {};
+template <> struct IsIntegral<long> : public TrueValue {};
+template <> struct IsIntegral<unsigned long> : public TrueValue {};
+template <> struct IsIntegral<long long> : public TrueValue {};
+template <> struct IsIntegral<unsigned long long> : public TrueValue {};
+template <> struct IsIntegral<bool> : public TrueValue {};
+
+template <typename Type> struct IsIntegralNotBool : public IsIntegral<Type> {};
+template <> struct IsIntegralNotBool<bool> : public FalseValue {};
+
+template <typename T> struct IsPointerType : public FalseValue {};
+template <typename T> struct IsPointerType<T *> : public TrueValue {};
+
+template <typename T1, typename T2> struct IsSame : public FalseValue {};
+template <typename T> struct IsSame<T, T> : public TrueValue {};
+
+} // namespace cpp
+} // namespace llvm_libc

libc/utils/UnitTest/CMakeLists.txt

 add_llvm_library(
   LibcUnitTest
   Test.cpp
   Test.h
   LINK_COMPONENTS Support
 )
+target_include_directories(LibcUnitTest PUBLIC ${LIBC_SOURCE_DIR})
+add_dependencies(LibcUnitTest standalone_cpp)

libc/utils/UnitTest/Test.h

 //===------------------ Base class for libc unittests -----------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
-// This file should stricly not include any other file. Not even standard
-// library headers.
+// This file can only include headers from utils/CPP/. No other header should be
+// included.
+
+#include "utils/CPP/TypeTraits.h"
 
 namespace llvm_libc {
 namespace testing {
 
-// We define our own EnableIf and IsIntegerType traits because we do not want to
-// include even the standard header <type_traits>.
-template <bool B, typename T> struct EnableIf;
-template <typename T> struct EnableIf<true, T> { typedef T Type; };
-
-template <bool B, typename T>
-using EnableIfType = typename EnableIf<B, T>::Type;
-
-template <typename Type> struct IsIntegerType {
-  static const bool Value = false;
-};
-
-template <> struct IsIntegerType<char> { static const bool Value = true; };
-template <> struct IsIntegerType<unsigned char> {
-  static const bool Value = true;
-};
-
-template <> struct IsIntegerType<short> { static const bool Value = true; };
-template <> struct IsIntegerType<unsigned short> {
-  static const bool Value = true;
-};
-
-template <> struct IsIntegerType<int> { static const bool Value = true; };
-template <> struct IsIntegerType<unsigned int> {
-  static const bool Value = true;
-};
-
-template <> struct IsIntegerType<long> { static const bool Value = true; };
-template <> struct IsIntegerType<unsigned long> {
-  static const bool Value = true;
-};
-
-template <> struct IsIntegerType<long long> { static const bool Value = true; };
-template <> struct IsIntegerType<unsigned long long> {
-  static const bool Value = true;
-};
-
-template <typename T> struct IsPointerType;
-
-template <typename T> struct IsPointerType<T *> {
-  static const bool Value = true;
-};
-
 class RunContext;
 
 // Only the following conditions are supported. Notice that we do not have
 // a TRUE or FALSE condition. That is because, C library funtions do not
 // return, but use integral return values to indicate true or false
 // conditions. Hence, it is more appropriate to use the other comparison
 // condtions for such cases.
 enum TestCondition {
   Cond_None,
   Cond_EQ,
   Cond_NE,
   Cond_LT,
   Cond_LE,
protected:
 
   // We make use of a template function, with |LHS| and |RHS| as explicit
   // parameters, for enhanced type checking. Other gtest like test unittest
   // frameworks have a similar functions which takes a boolean argument
   // instead of the explicit |LHS| and |RHS| arguments. This boolean argument
   // is the result of the |Cond| operation on |LHS| and |RHS|. Though not bad,
   // mismatched |LHS| and |RHS| types can potentially succeed because of type
   // promotion.
-  template <typename ValType,
-            EnableIfType<IsIntegerType<ValType>::Value, ValType> = 0>
+  template <
+      typename ValType,
+      cpp::EnableIfType<cpp::IsIntegralNotBool<ValType>::Value, ValType> = 0>
   static bool test(RunContext &Ctx, TestCondition Cond, ValType LHS,
                    ValType RHS, const char *LHSStr, const char *RHSStr,
                    const char *File, unsigned long Line) {
     return internal::test(Ctx, Cond, LHS, RHS, LHSStr, RHSStr, File, Line);
   }
 
-  template <typename ValType,
-            EnableIfType<IsPointerType<ValType>::Value, ValType> = nullptr>
+  template <
+      typename ValType,
+      cpp::EnableIfType<cpp::IsPointerType<ValType>::Value, ValType> = nullptr>
   static bool test(RunContext &Ctx, TestCondition Cond, ValType LHS,
                    ValType RHS, const char *LHSStr, const char *RHSStr,
                    const char *File, unsigned long Line) {
     return internal::test(Ctx, Cond, (unsigned long long)LHS,
                           (unsigned long long)RHS, LHSStr, RHSStr, File, Line);
   }
 
   static bool testStrEq(RunContext &Ctx, const char *LHS, const char *RHS,