Remove dependency on system include dir

external/external.cmake

@@ -181,20 +181,6 @@ function(_cppast_find_libclang config_tool min_version force)
         endif()
     endif()
 
-    # find system header files in llvm_library_dir
-    if(${force})
-        unset(LIBCLANG_SYSTEM_INCLUDE_DIR CACHE)
-    endif()
-    if(NOT LIBCLANG_SYSTEM_INCLUDE_DIR)
-        find_path(LIBCLANG_SYSTEM_INCLUDE_DIR "stddef.h" "${llvm_library_dir}/clang/${llvm_version}/include" NO_DEFAULT_PATH)
-
-        if(NOT LIBCLANG_SYSTEM_INCLUDE_DIR)
-            message(FATAL_ERROR "libclang system header files not found")
-        else()
-            message(STATUS "Found libclang system header files at ${LIBCLANG_SYSTEM_INCLUDE_DIR}")
-        endif()
-    endif()
-
     # find clang binary in llvm_binary_dir
     # note: never override that binary
     if(NOT CLANG_BINARY)
@@ -238,6 +224,5 @@ add_library(_cppast_libclang INTERFACE)
 target_link_libraries(_cppast_libclang INTERFACE ${LIBCLANG_LIBRARY})
 target_include_directories(_cppast_libclang INTERFACE ${LIBCLANG_INCLUDE_DIR})
 target_compile_definitions(_cppast_libclang INTERFACE
-                           CPPAST_LIBCLANG_SYSTEM_INCLUDE_DIR="${LIBCLANG_SYSTEM_INCLUDE_DIR}"
                            CPPAST_CLANG_BINARY="${CLANG_BINARY}"
                            CPPAST_CLANG_VERSION_STRING="${LLVM_VERSION}")

include/cppast/libclang_parser.hpp

@@ -120,7 +120,9 @@ public:
     /// binary.
     /// If the binary is not found, it will try and search for it.
     /// \returns `true` if the binary was found exactly as specified.
-    /// \notes It will be used for preprocessing.
+    /// \notes This binary will be used for preprocessing as well as determining the default include
+    /// directories. As such, if it is called after include directories have already been added, the
+    /// order might end up being wrong.
     bool set_clang_binary(std::string binary);
 
     /// \effects Sets whether or not the preprocessed file will be written out.

src/libclang/libclang_parser.cpp

@@ -76,6 +76,9 @@ bool libclang_compilation_database::has_config(const char* file_name) const
     return true;
 }
 
+namespace
+{} // namespace
+
 libclang_compile_config::libclang_compile_config()
 : compile_config({}), write_preprocessed_(false), fast_preprocessing_(false),
   remove_comments_in_macro_(false)
@@ -83,9 +86,6 @@ libclang_compile_config::libclang_compile_config()
     // set given clang binary
     set_clang_binary(CPPAST_CLANG_BINARY);
 
-    // set system include dir
-    add_include_dir(CPPAST_LIBCLANG_SYSTEM_INCLUDE_DIR);
-
     // set macros to detect cppast
     define_macro("__cppast__", "libclang");
     define_macro("__cppast_version_major__", CPPAST_VERSION_MAJOR);
@@ -252,6 +252,37 @@ bool is_valid_binary(const std::string& binary)
                          [](const char*, std::size_t) {});
     return process.get_exit_status() == 0;
 }
+
+void add_default_include_dirs(libclang_compile_config& config)
+{
+    std::string  verbose_output;
+    tpl::Process process(detail::libclang_compile_config_access::clang_binary(config)
+                             + " -x c++ -v -",
+                         "", [](const char*, std::size_t) {},
+                         [&](const char* str, std::size_t n) { verbose_output.append(str, n); },
+                         true);
+    process.write("", 1);
+    process.close_stdin();
+    process.get_exit_status();
+
+    auto pos = verbose_output.find("#include <...>");
+    DEBUG_ASSERT(pos != std::string::npos, detail::assert_handler{});
+    while (verbose_output[pos] != '\n')
+        ++pos;
+    ++pos;
+
+    // now every line is an include path, starting with a space
+    while (verbose_output[pos] == ' ')
+    {
+        auto start = pos + 1;
+        while (verbose_output[pos] != '\n')
+            ++pos;
+        auto end = pos;
+        ++pos;
+
+        config.add_include_dir(verbose_output.substr(start, end - start));
+    }
+}
 } // namespace
 
 bool libclang_compile_config::set_clang_binary(std::string binary)
@@ -259,6 +290,7 @@ bool libclang_compile_config::set_clang_binary(std::string binary)
     if (is_valid_binary(binary))
     {
         clang_binary_ = binary;
+        add_default_include_dirs(*this);
         return true;
     }
     else
@@ -271,6 +303,7 @@ bool libclang_compile_config::set_clang_binary(std::string binary)
             if (is_valid_binary(p))
             {
                 clang_binary_ = p;
+                add_default_include_dirs(*this);
                 return false;
             }
 

test/libclang_parser.cpp

@@ -23,9 +23,15 @@ void require_flags(const libclang_compile_config& config, const char* flags)
 {
     std::string result;
     auto        config_flags = detail::libclang_compile_config_access::flags(config);
-    // skip first 4, those are the default options
+    // skip until including __cppast_version__minor__, those are the default options
-    for (auto iter = config_flags.begin() + 4; iter != config_flags.end(); ++iter)
+    auto in_default = true;
-        result += *iter + ' ';
+    for (auto iter = config_flags.begin(); iter != config_flags.end(); ++iter)
+    {
+        if (*iter == "-D__cppast_version_minor__=\"" CPPAST_VERSION_MINOR "\"")
+            in_default = false;
+        else if (!in_default)
+            result += *iter + ' ';
+    }
     result.pop_back();
     REQUIRE(result == flags);
 }

test/test_parser.hpp

@@ -23,14 +23,21 @@ inline void write_file(const char* name, const char* code)
     file << code;
 }
 
-inline std::unique_ptr<cppast::cpp_file> parse_file(const cppast::cpp_entity_index& idx,
+inline cppast::libclang_compile_config make_test_config()
-                                                    const char*                     name,
-                                                    bool fast_preprocessing = false)
 {
     using namespace cppast;
 
     libclang_compile_config config;
     config.set_flags(cpp_standard::cpp_latest);
+    return config;
+}
+
+inline std::unique_ptr<cppast::cpp_file> parse_file(const cppast::cpp_entity_index& idx,
+                                                    const char*                     name,
+                                                    bool fast_preprocessing = false)
+{
+    using namespace cppast;
+    static auto config = make_test_config();
     config.fast_preprocessing(fast_preprocessing);
 
     libclang_parser p(default_logger());