enable boost json (#1292)

* bump boost.json and see if it works in simdjson CI

* enable boost json

* clean up

* add boost json to deps

* use boost if std::string_view is available

* add build with c++20

* use docker image which has the proper libc++ installed

.drone.yml

@@ -183,6 +183,27 @@ steps:
     - ASAN_OPTIONS="detect_leaks=0" ctest $CTEST_FLAGS -LE "acceptance|per_implementation" # Everything we haven't run yet, run now.
 ---
 kind: pipeline
+name: cpp20-clang11-libcpp
+platform: { os: linux, arch: amd64 }
+steps:
+- name: Build and Test
+  image: pauldreik/llvm-11
+  user: root
+  environment:
+    CC: clang-11
+    CXX: clang++-11
+    CMAKE_FLAGS: -GNinja
+    BUILD_FLAGS:
+    CTEST_FLAGS: -j4 --output-on-failure -E checkperf
+    CXXFLAGS: -std=c++20 -stdlib=libc++
+  commands:
+    - mkdir build
+    - cd build
+    - cmake $CMAKE_FLAGS ..
+    - cmake --build . $BUILD_FLAGS
+    - ctest $CTEST_FLAGS
+---
+kind: pipeline
 name: arm64-gcc8
 platform: { os: linux, arch: arm64 }
 steps:

benchmark/parsingcompetition.cpp

@@ -27,13 +27,7 @@ SIMDJSON_PUSH_DISABLE_ALL_WARNINGS
 #include <nlohmann/json.hpp>
 using json = nlohmann::json;
 
-#if defined(__clang__)
-// Under some clang/libc++ configurations, boost json fails
-// to build.
-#define DISABLE_BOOST_JSON
-#endif
-
-#ifndef DISABLE_BOOST_JSON
+#ifdef HAS_BOOST_JSON
 #include <boost/json/parser.hpp>
 #include <boost/json/monotonic_resource.hpp>
 #endif
@@ -185,7 +179,7 @@ bool bench(const char *filename, bool verbose, bool just_data,
             std::memcpy(buffer, p.data(), p.size()) &&
                 (buffer[p.size()] = '\0'),
             repeat, volume, !just_data);
-#ifndef DISABLE_BOOST_JSON
+#ifdef HAS_BOOST_JSON
   {
     const boost::json::string_view sv(p.data(), p.size());
     boost::json::parser p;

dependencies/CMakeLists.txt

@@ -14,9 +14,11 @@ endif()
 # This prevents variables declared with set() from unnecessarily escaping and
 # should not be called more than once
 function(competition_scope_)
-  # Boost JSON is not compatible with some clang/libc++ configurations.
-  if(NOT CMAKE_CXX_COMPILER_ID MATCHES "Clang")
-    import_dependency(boostjson CPPAlliance/json a0983f7)
+  # boost json in standalone mode requires C++17 string_view
+  include(CheckCXXSourceCompiles)
+  check_cxx_source_compiles("#include <string_view>\n#if __cpp_lib_string_view < 201606\n#error no string view support\n#endif\nint main(){}" USE_BOOST_JSON)
+  if(USE_BOOST_JSON)
+  import_dependency(boostjson boostorg/json ee8d72d8502b409b5561200299cad30ccdb91415)
   add_library(boostjson STATIC "${boostjson_SOURCE_DIR}/src/src.cpp")
   target_compile_definitions(boostjson PUBLIC BOOST_JSON_STANDALONE)
   target_include_directories(boostjson SYSTEM PUBLIC
@@ -87,7 +89,8 @@ function(competition_scope_)
 
   add_library(competition-core INTERFACE)
   target_link_libraries(competition-core INTERFACE nlohmann_json rapidjson sajson cjson jsmn yyjson)
-  if(NOT CMAKE_CXX_COMPILER_ID MATCHES "Clang")
+  if(USE_BOOST_JSON)
+     target_compile_definitions(boostjson INTERFACE HAS_BOOST_JSON)
      target_link_libraries(competition-core INTERFACE boostjson)
   endif()