[libc++] [P1208] [C++20] Adopt source location from Library Fundamentals V3 for C++20.

[curdeius]

Summary

Implements source_location.

[curdeius]

• Add new header to CMake, double-include test and module map.

[ldionne]

Thanks for the contribution! This looks pretty good, however I would like to see tests where current() is called in some full-expression with other expressions in it, in a default member initializer, etc.

http://eel.is/c++draft/support.srcloc.class#lib:source_location specifies the intended behavior of source_location in various special cases (like http://eel.is/c++draft/support.srcloc.class#support.srcloc.cons-2), and we should have tests for those.

Also, is there a reason why the runtime and the constexpr tests can't be identical to each other? It looks like some of your coverage is only on constexpr tests, and other coverage is only on the runtime tests.

libcxx/include/source_location

48

I think we need to figure out this issue before we move forward.

libcxx/test/std/language.support/reflection.src_loc/creation/source_location.pass.cpp

29 ↗

(On Diff #265493)

We can't test it that way because the standard says it's unspecified what it returns. I think those need to be libc++ specific tests.

libcxx/test/std/language.support/reflection.src_loc/fields/column.pass.cpp

21 ↗

(On Diff #265493)

Should we add ASSERT_NOEXCEPT(loc.column())? This also applies to the other accessors AFAICT.

libcxx/test/std/language.support/reflection.src_loc/fields/file_name.pass.cpp

25 ↗

(On Diff #265493)

Like mentioned above, this needs to be a libc++ specific assertion.

libcxx/test/std/language.support/reflection.src_loc/fields/line.pass.cpp

37 ↗

(On Diff #265493)

Inconsistent indentation.

[curdeius]

Thanks for the review.

libcxx/test/std/language.support/reflection.src_loc/fields/line.pass.cpp

37 ↗

(On Diff #265493)

I think that you mistaken it with the above line which parameter list, hence indented differently.

[ldionne]

libcxx/test/std/language.support/reflection.src_loc/fields/line.pass.cpp

37 ↗

(On Diff #265493)

Agreed, please disregard that comment.

[curdeius]

• Rebase.
• Address review comments.

[curdeius]

libcxx/include/source_location

48

I still don't know why it doesn't work with consteval, but I've seen that libstdc++ experimental implementation also uses constexpr here: https://github.com/gitGNU/gcc/blob/master/libstdc%2B%2B-v3/include/experimental/source_location#L50
Also, I've just rechecked it and it only fails with gcc, it passes all the tests with clang 10.
I remember however doing some manual testing on clang on Windows (an older version, probably 9) and it was failing too.
I'll check how other clang versions behave.

[curdeius]

Ok, so clang 8 doesn't support consteval. It also doesn't have required builtins (__builtin_FILE etc.). consteval works ok on clang 9+.
How can I mark tests as unsupported when the builtins are not supported? (a good example would be column.pass.cpp test that I disabled for gcc that doesn't have __builtin_COLUMN)

[curdeius]

libcxx/test/std/language.support/support.srcloc/obs/column.pass.cpp

11

Should I use XFAIL instead of UNSUPPORTED so that the test breaks when gcc adds this builtin?

[ldionne]

In D80376#2100390, @curdeius wrote:

Ok, so clang 8 doesn't support consteval. It also doesn't have required builtins (__builtin_FILE etc.). consteval works ok on clang 9+.
How can I mark tests as unsupported when the builtins are not supported? (a good example would be column.pass.cpp test that I disabled for gcc that doesn't have __builtin_COLUMN)

Can you mark it as unsupported on the specific compiler versions?

libcxx/test/std/language.support/support.srcloc/obs/column.pass.cpp

11

If you use UNSUPPORTED: gcc-x, gcc-y, gcc-z, then you won't have this problem. WDYT?

Otherwise, XFAIL seems to me like a good idea indeed.

[EricWF]

This is not the ABI we want.

[ldionne]

In D80376#2101587, @EricWF wrote:

This is not the ABI we want.

Are you thinking of a single pointer to information stored in the data segment by the compiler?

[EricWF]

In D80376#2101677, @ldionne wrote:

In D80376#2101587, @EricWF wrote:

This is not the ABI we want.

Are you thinking of a single pointer to information stored in the data segment by the compiler?

Yes, sorry. I should have stated that initially. We need source location to be as low cost as possible to copy.
It should only consume a single register.

Please feel free to reach out via email or chat and we can discuss ideas on achieving this in more depth.

[curdeius]

• Use precise compiler versions in UNSUPPORTED.

[curdeius]

I've updated the "unsupported" comments with precise compiler versions. I cannot test apple-clang though.
Anyway, I'll put this revision into hibernation until there's a builtin for a single-pointer source location (whether it be __bultin_source_location or T* __builtin_static_storage_duration(T)).

[curdeius]

libcxx/test/libcxx/language.support/support.srcloc/source_location.pass.cpp

23

Note to myself: add a test verifying assert(sizeof(source_location) == sizeof(void*)).

[smeenai]

In D80376#2102805, @curdeius wrote:

I've updated the "unsupported" comments with precise compiler versions. I cannot test apple-clang though.
Anyway, I'll put this revision into hibernation until there's a builtin for a single-pointer source location (whether it be __bultin_source_location or T* __builtin_static_storage_duration(T)).

Any updates here? I saw some internal interest around source_location today and was curious about the status of this.

[curdeius]

Cf. https://reviews.llvm.org/D120634

libcxx/docs/FeatureTestMacroTable.rst

.. table:: Current Status
     ``__cpp_lib_interpolate``                         ``201902L``      
     ------------------------------------------------- -----------------
     ``__cpp_lib_is_constant_evaluated``               ``201811L``      
     ------------------------------------------------- -----------------
     ``__cpp_lib_list_remove_return_type``             ``201806L``      
     ------------------------------------------------- -----------------
     ``__cpp_lib_ranges``                              *unimplemented*  
     ------------------------------------------------- -----------------
+    ``__cpp_lib_source_location``                     ``201907L``      
+    ------------------------------------------------- -----------------
     ``__cpp_lib_span``                                ``202002L``      
     ------------------------------------------------- -----------------
     ``__cpp_lib_three_way_comparison``                *unimplemented*  
     ------------------------------------------------- -----------------
     ``__cpp_lib_to_array``                            ``201907L``      
     ================================================= =================
 
 

libcxx/include/CMakeLists.txt

set(files
   random
   ratio
   regex
   scoped_allocator
   semaphore
   set
   setjmp.h
   shared_mutex
+  source_location
   span
   sstream
   stack
   stdbool.h
   stddef.h
   stdexcept
   stdint.h
   stdio.h

libcxx/include/module.modulemap

module experimental {
     module simd {
       header "experimental/simd"
       export *
     }
     module set {
       header "experimental/set"
       export *
     }
+    module source_location {
+      header "source_location"
+      export *
+    }
     module span {
       header "span"
       export *
     }
     module string {
       header "experimental/string"
       export *
     }

libcxx/include/source_location

+// -*- C++ -*-
+//===------------------------------ source_location ----------------------===//
+//
+// 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
+//
+//===---------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_SOURCE_LOCATION
+#define _LIBCPP_SOURCE_LOCATION
+
+/*
+    source_location synopsis
+
+namespace std {
+  struct source_location {
+    // source location construction
+    static consteval source_location current() noexcept;
+    constexpr source_location() noexcept;
+
+    // source location field access
+    constexpr uint_least32_t line() const noexcept;
+    constexpr uint_least32_t column() const noexcept;
+    constexpr const char* file_name() const noexcept;
+    constexpr const char* function_name() const noexcept;
+
+  private:
+    uint_least32_t line_;        // exposition only
+    uint_least32_t column_;      // exposition only
+    const char* file_name_;      // exposition only
+    const char* function_name_;  // exposition only
+  };
+}
+*/
+
+#include <__config>
+#include <cstdint>
+#include <type_traits>
+#include <version>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER > 17
+
+struct source_location {
+  // TODO: current() should be marked consteval instead of constexpr,
+  // but current compiler implementations seem buggy and return callee's location.
+  static constexpr source_location
+  current(const char* __file = __builtin_FILE(),
+          const char* __func = __builtin_FUNCTION(),
+          uint_least32_t __line = __builtin_LINE(),
+#if __has_builtin(__builtin_COLUMN)
+          uint_least32_t __col = __builtin_COLUMN()) noexcept {
+#else
+          uint_least32_t __col = 0) noexcept {
+#endif
+    source_location __sloc;
+    __sloc.__file = __file;
+    __sloc.__func = __func;
+    __sloc.__line = __line;
+    __sloc.__col = __col;
+    return __sloc;
+  }
+
+  constexpr source_location() noexcept : __file("unknown"),
+                                         __func(__file),
+                                         __line(0),
+                                         __col(0) {}
+
+  constexpr uint_least32_t line() const noexcept { return __line; }
+  constexpr uint_least32_t column() const noexcept { return __col; }
+  constexpr const char* file_name() const noexcept { return __file; }
+  constexpr const char* function_name() const noexcept { return __func; }
+
+private:
+  const char* __file;
+  const char* __func;
+  uint_least32_t __line;
+  uint_least32_t __col;
+};
+
+#endif // _LIBCPP_STD_VER > 17
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP_SOURCE_LOCATION

libcxx/include/version

 __cpp_lib_result_of_sfinae                              201210L <functional> <type_traits>
 __cpp_lib_robust_nonmodifying_seq_ops                   201304L <algorithm>
 __cpp_lib_sample                                        201603L <algorithm>
 __cpp_lib_scoped_lock                                   201703L <mutex>
 __cpp_lib_shared_mutex                                  201505L <shared_mutex>
 __cpp_lib_shared_ptr_arrays                             201611L <memory>
 __cpp_lib_shared_ptr_weak_type                          201606L <memory>
 __cpp_lib_shared_timed_mutex                            201402L <shared_mutex>
+__cpp_lib_source_location                               201907L <source_location>
 __cpp_lib_span                                          202002L <span>
 __cpp_lib_string_udls                                   201304L <string>
 __cpp_lib_string_view                                   201606L <string> <string_view>
 __cpp_lib_three_way_comparison                          201711L <compare>
 __cpp_lib_to_array                                      201907L <array>
 __cpp_lib_to_chars                                      201611L <utility>
 __cpp_lib_transformation_trait_aliases                  201304L <type_traits>
 __cpp_lib_transparent_operators                         201510L <functional>

 # define __cpp_lib_erase_if                             202002L
 // # define __cpp_lib_generic_unordered_lookup             201811L
 # define __cpp_lib_interpolate                          201902L
 # if !defined(_LIBCPP_HAS_NO_BUILTIN_IS_CONSTANT_EVALUATED)
 #   define __cpp_lib_is_constant_evaluated              201811L
 # endif
 # define __cpp_lib_list_remove_return_type              201806L
 // # define __cpp_lib_ranges                               201811L
+# define __cpp_lib_source_location                      201907L
 # define __cpp_lib_span                                 202002L
 // # define __cpp_lib_three_way_comparison                 201711L
 # define __cpp_lib_to_array                             201907L
 #endif
 
 #endif // _LIBCPP_VERSIONH

libcxx/test/libcxx/double_include.sh.cpp

 #include <ratio>
 #include <regex>
 #include <scoped_allocator>
 #include <set>
 #include <setjmp.h>
 #ifndef _LIBCPP_HAS_NO_THREADS
 #include <shared_mutex>
 #endif
+#include <source_location>
 #include <span>
 #include <sstream>
 #include <stack>
 #include <stdbool.h>
 #include <stddef.h>
 #include <stdexcept>
 #include <stdint.h>
 #include <stdio.h>

libcxx/test/libcxx/language.support/support.srcloc/source_location.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// UNSUPPORTED: clang-8, clang-7, clang-6
+
+// <source_location>
+
+// source_location::source_location();
+
+#include <source_location>
+#include <cassert>
+#include <string_view>
+
+#include "test_macros.h"
+
+constexpr bool test() {
+  using SV = std::string_view;
+
+  std::source_location loc;
+
+  assert(loc.line() == 0u);
+  assert(loc.column() == 0u);
+  assert(SV{loc.file_name()} == "unknown");
+  assert(SV{loc.function_name()} == "unknown");
+
+  ASSERT_NOEXCEPT(std::source_location());
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}

libcxx/test/std/language.support/support.limits/support.limits.general/source_location.version.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+//
+// WARNING: This test was generated by generate_feature_test_macro_components.py
+// and should not be edited manually.
+
+// <source_location>
+
+// Test the feature test macros defined by <source_location>
+
+/*  Constant                     Value
+    __cpp_lib_source_location    201907L [C++2a]
+*/
+
+#include <source_location>
+#include "test_macros.h"
+
+#if TEST_STD_VER < 14
+
+#ifdef __cpp_lib_source_location
+#error "__cpp_lib_source_location should not be defined before c++2a"
+#endif
+
+#elif TEST_STD_VER == 14
+
+#ifdef __cpp_lib_source_location
+#error "__cpp_lib_source_location should not be defined before c++2a"
+#endif
+
+#elif TEST_STD_VER == 17
+
+#ifdef __cpp_lib_source_location
+#error "__cpp_lib_source_location should not be defined before c++2a"
+#endif
+
+#elif TEST_STD_VER > 17
+
+#ifndef __cpp_lib_source_location
+#error "__cpp_lib_source_location should be defined in c++2a"
+#endif
+#if __cpp_lib_source_location != 201907L
+#error "__cpp_lib_source_location should have the value 201907L in c++2a"
+#endif
+
+#endif // TEST_STD_VER > 17
+
+int main(int, char**) { return 0; }

libcxx/test/std/language.support/support.limits/support.limits.general/version.version.pass.cpp

/*  Constant                                       Value
     __cpp_lib_result_of_sfinae                     201210L [C++14]
     __cpp_lib_robust_nonmodifying_seq_ops          201304L [C++14]
     __cpp_lib_sample                               201603L [C++17]
     __cpp_lib_scoped_lock                          201703L [C++17]
     __cpp_lib_shared_mutex                         201505L [C++17]
     __cpp_lib_shared_ptr_arrays                    201611L [C++17]
     __cpp_lib_shared_ptr_weak_type                 201606L [C++17]
     __cpp_lib_shared_timed_mutex                   201402L [C++14]
+    __cpp_lib_source_location                      201907L [C++2a]
     __cpp_lib_span                                 202002L [C++2a]
     __cpp_lib_string_udls                          201304L [C++14]
     __cpp_lib_string_view                          201606L [C++17]
     __cpp_lib_three_way_comparison                 201711L [C++2a]
     __cpp_lib_to_array                             201907L [C++2a]
     __cpp_lib_to_chars                             201611L [C++17]
     __cpp_lib_transformation_trait_aliases         201304L [C++14]
     __cpp_lib_transparent_operators                201210L [C++14]

 # ifdef __cpp_lib_shared_ptr_weak_type
 #   error "__cpp_lib_shared_ptr_weak_type should not be defined before c++17"
 # endif
 
 # ifdef __cpp_lib_shared_timed_mutex
 #   error "__cpp_lib_shared_timed_mutex should not be defined before c++14"
 # endif
 
+#ifdef __cpp_lib_source_location
+#error "__cpp_lib_source_location should not be defined before c++2a"
+#endif
+
 # ifdef __cpp_lib_span
 #   error "__cpp_lib_span should not be defined before c++2a"
 # endif
 
 # ifdef __cpp_lib_string_udls
 #   error "__cpp_lib_string_udls should not be defined before c++14"
 # endif
 

 #     error "__cpp_lib_shared_timed_mutex should have the value 201402L in c++14"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_timed_mutex
 #     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
 #   endif
 # endif
 
+#ifdef __cpp_lib_source_location
+#error "__cpp_lib_source_location should not be defined before c++2a"
+#endif
+
 # ifdef __cpp_lib_span
 #   error "__cpp_lib_span should not be defined before c++2a"
 # endif
 
 # ifndef __cpp_lib_string_udls
 #   error "__cpp_lib_string_udls should be defined in c++14"
 # endif
 # if __cpp_lib_string_udls != 201304L

 #     error "__cpp_lib_shared_timed_mutex should have the value 201402L in c++17"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_timed_mutex
 #     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
 #   endif
 # endif
 
+#ifdef __cpp_lib_source_location
+#error "__cpp_lib_source_location should not be defined before c++2a"
+#endif
+
 # ifdef __cpp_lib_span
 #   error "__cpp_lib_span should not be defined before c++2a"
 # endif
 
 # ifndef __cpp_lib_string_udls
 #   error "__cpp_lib_string_udls should be defined in c++17"
 # endif
 # if __cpp_lib_string_udls != 201304L

 #     error "__cpp_lib_shared_timed_mutex should have the value 201402L in c++2a"
 #   endif
 # else
 #   ifdef __cpp_lib_shared_timed_mutex
 #     error "__cpp_lib_shared_timed_mutex should not be defined when !defined(_LIBCPP_HAS_NO_THREADS) is not defined!"
 #   endif
 # endif
 
+#ifndef __cpp_lib_source_location
+#error "__cpp_lib_source_location should be defined in c++2a"
+#endif
+#if __cpp_lib_source_location != 201907L
+#error "__cpp_lib_source_location should have the value 201907L in c++2a"
+#endif
+
 # ifndef __cpp_lib_span
 #   error "__cpp_lib_span should be defined in c++2a"
 # endif
 # if __cpp_lib_span != 202002L
 #   error "__cpp_lib_span should have the value 202002L in c++2a"
 # endif
 
 # ifndef __cpp_lib_string_udls

libcxx/test/std/language.support/support.srcloc/class/source_location.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// UNSUPPORTED: clang-8, clang-7, clang-6
+
+// <source_location>
+
+// source_location::source_location();
+
+#include <source_location>
+#include <cassert>
+#include <string_view>
+#include <type_traits>
+
+#include "test_macros.h"
+
+constexpr bool test() {
+  static_assert(std::is_nothrow_move_constructible_v<std::source_location>,
+                "support.srcloc.cons (1.1)");
+  static_assert(std::is_nothrow_move_assignable_v<std::source_location>,
+                "support.srcloc.cons (1.2)");
+  static_assert(std::is_nothrow_swappable_v<std::source_location>,
+                "support.srcloc.cons (1.3)");
+
+  using SV = std::string_view;
+
+  const std::source_location loc1 = std::source_location::current();
+
+  std::source_location loc2 = loc1;
+  assert(loc1.line() == loc2.line());                           // (3.1)
+  assert(loc1.column() == loc2.column());                       // (3.2)
+  assert(SV{loc1.file_name()} == SV{loc2.file_name()});         // (3.3)
+  assert(SV{loc1.function_name()} == SV{loc2.function_name()}); // (3.4)
+
+  std::source_location loc3 = std::move(loc2);
+  assert(SV{loc1.file_name()} == SV{loc3.file_name()});         // (3.1)
+  assert(SV{loc1.function_name()} == SV{loc3.function_name()}); // (3.2)
+  assert(loc1.line() == loc3.line());                           // (3.3)
+  assert(loc1.column() == loc3.column());                       // (3.4)
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}

libcxx/test/std/language.support/support.srcloc/cons/current.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// UNSUPPORTED: clang-8, clang-7, clang-6
+
+// <source_location>
+
+// source_location::current();
+
+#include <source_location>
+#include <cassert>
+#include <string_view>
+
+#include "test_macros.h"
+
+using srcloc = std::source_location;
+
+struct s {
+  srcloc member = srcloc::current();
+  int other_member{};
+
+  constexpr s(srcloc loc = srcloc::current())
+      : member{loc}
+  // values of member refer to the location of the calling function ([dcl.fct.default])
+  {}
+
+  static constexpr srcloc before_int_ctor = srcloc::current();
+  constexpr s(int blather)
+      : other_member(blather) // values of member refer to this location
+  {}
+  static constexpr srcloc after_int_ctor = srcloc::current();
+
+  static constexpr srcloc before_double_ctor = srcloc::current();
+  constexpr s(double) // values of member refer to this location
+  {}
+  static constexpr srcloc after_double_ctor = srcloc::current();
+};
+
+constexpr bool test_member() {
+  srcloc before = srcloc::current();
+  s s_srcloc;
+  srcloc after = srcloc::current();
+  assert(s_srcloc.member.line() > before.line());
+  assert(s_srcloc.member.line() < after.line());
+
+  s s_int(int{});
+  assert(s_int.member.line() > s::before_int_ctor.line());
+  assert(s_int.member.line() < s::after_int_ctor.line());
+  // clang returns ctor name location
+  // gcc returns end of initializer list location
+
+  s s_double(double{});
+  assert(s_double.member.line() > s::before_double_ctor.line());
+  assert(s_double.member.line() < s::after_double_ctor.line());
+  // clang returns ctor name location
+  // gcc returns opening brace location
+
+  return true;
+}
+
+constexpr bool test_parameter(srcloc loc = srcloc::current()) {
+  using SV = std::string_view;
+
+  assert(loc.line() > __LINE__); // In test().
+  // We do not test column here, as gcc always sets it to 0.
+  assert(SV{loc.file_name()}.ends_with("current.pass.cpp"));
+  assert(SV{loc.function_name()} == "test");
+
+  ASSERT_NOEXCEPT(srcloc::current());
+
+  return true;
+}
+
+constexpr bool test() {
+  test_parameter();
+  test_member();
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}

libcxx/test/std/language.support/support.srcloc/obs/column.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// GCC does not have __builtin_COLUMN.
+// UNSUPPORTED: gcc-10, gcc-9, gcc-8
+// UNSUPPORTED: clang-8, clang-7, clang-6
+
+// <source_location>
+
+// source_location::column();
+
+#include <source_location>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr bool test() {
+  std::source_location loc1;
+  assert(loc1.column() == 0u);
+  std::source_location loc2 = std::source_location::current();
+  assert(loc2.column() == 31u);
+  std::source_location loc3 = // Comment to change column.
+      std::source_location::current();
+  assert(loc3.column() == 7u);
+
+  ASSERT_NOEXCEPT(loc1.column());
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}

libcxx/test/std/language.support/support.srcloc/obs/file_name.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// UNSUPPORTED: clang-8, clang-7, clang-6
+
+// <source_location>
+
+// source_location::file_name();
+
+#include <source_location>
+#include <cassert>
+#include <string_view>
+
+#include "test_macros.h"
+
+constexpr bool test() {
+  using SV = std::string_view;
+
+  std::source_location loc = std::source_location::current();
+  assert(SV{loc.file_name()}.ends_with("file_name.pass.cpp"));
+
+  ASSERT_NOEXCEPT(loc.file_name());
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}

libcxx/test/std/language.support/support.srcloc/obs/function_name.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// UNSUPPORTED: clang-8, clang-7, clang-6
+
+// <source_location>
+
+// source_location::function_name();
+
+#include <source_location>
+#include <cassert>
+#include <string_view>
+
+#include "test_macros.h"
+
+constexpr bool test() {
+  using SV = std::string_view;
+
+  std::source_location loc = std::source_location::current();
+  assert(SV{loc.function_name()} == "test");
+
+  ASSERT_NOEXCEPT(loc.function_name());
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}

libcxx/test/std/language.support/support.srcloc/obs/line.pass.cpp

+//===----------------------------------------------------------------------===//
+//
+// 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
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// UNSUPPORTED: clang-8, clang-7, clang-6
+
+// <source_location>
+
+// source_location::line();
+
+#include <source_location>
+#include <cassert>
+
+#include "test_macros.h"
+
+constexpr bool
+test_caller(std::source_location loc = std::source_location::current()) {
+  assert(loc.line() > __LINE__);
+
+  return true;
+}
+
+constexpr bool test() {
+  std::source_location loc1;
+  assert(loc1.line() == 0u);
+  std::source_location loc2 = std::source_location::current();
+  assert(loc2.line() == __LINE__ - 1u);
+
+  test_caller();
+
+  ASSERT_NOEXCEPT(loc1.line());
+
+  return true;
+}
+
+int main(int, char**) {
+  test();
+  static_assert(test());
+
+  return 0;
+}

libcxx/utils/generate_feature_test_macro_components.py

feature_test_macros = sorted([ add_version_header(x) for x in [
    "headers": ["bit"],
    },
   {"name": "__cpp_lib_to_array",
    "values": {
      "c++2a": int(201907),
    },
    "headers": ["array"],
    },
+  {"name": "__cpp_lib_source_location",
+   "values": {
+     "c++2a": int(201907),
+   },
+   "headers": ["source_location"],
+   },
   {"name": "__cpp_lib_span",
    "values": {
      "c++2a": int(202002),
    },
    "headers": ["span"],
    },
 ]], key=lambda tc: tc["name"])
 

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