Add support for C language standards

include/cppast/compile_config.hpp

@@ -15,7 +15,7 @@
 
 namespace cppast
 {
-/// The C++ standard that should be used.
+/// The C/C++ standard that should be used.
 enum class cpp_standard
 {
     cpp_98,
@@ -28,7 +28,14 @@ enum class cpp_standard
     cpp_20,
     cpp_2b,
 
+    c_89,
+    c_99,
+    c_11,
+    c_17,
+    c_2x,
+
     cpp_latest = cpp_standard::cpp_14, //< The latest supported C++ standard.
+    c_latest = cpp_standard::c_17, //< The latest supported C standard.
 };
 
 /// \returns A human readable string representing the option,
@@ -55,12 +62,50 @@ inline const char* to_string(cpp_standard standard) noexcept
         return "c++20";
     case cpp_standard::cpp_2b:
         return "c++2b";
+
+    case cpp_standard::c_89:
+        return "c89";
+    case cpp_standard::c_99:
+        return "c99";
+    case cpp_standard::c_11:
+        return "c11";
+    case cpp_standard::c_17:
+        return "c17";
+    case cpp_standard::c_2x:
+        return "c2x";
     }
 
     DEBUG_UNREACHABLE(detail::assert_handler{});
     return "ups";
 }
 
+/// \returns whether the language standard is a C standard
+inline bool is_c_standard(cpp_standard standard) noexcept
+{
+    switch (standard)
+    {
+    case cpp_standard::cpp_98:
+    case cpp_standard::cpp_03:
+    case cpp_standard::cpp_11:
+    case cpp_standard::cpp_14:
+    case cpp_standard::cpp_1z:
+    case cpp_standard::cpp_17:
+    case cpp_standard::cpp_2a:
+    case cpp_standard::cpp_20:
+    case cpp_standard::cpp_2b:
+        return false;
+    case cpp_standard::c_89:
+    case cpp_standard::c_99:
+    case cpp_standard::c_11:
+    case cpp_standard::c_17:
+    case cpp_standard::c_2x:
+        return true;
+    }
+
+    DEBUG_UNREACHABLE(detail::assert_handler{});
+    return false;
+}
+
 /// Other special compilation flags.
 enum class compile_flag
 {
@@ -117,6 +162,12 @@ class compile_config
         return do_get_name();
     }
 
+    /// \returns Whether to parse files as C rather than C++.
+    bool use_c() const noexcept
+    {
+        return do_use_c();
+    }
+
 protected:
     compile_config(std::vector<std::string> def_flags) : flags_(std::move(def_flags)) {}
 
@@ -160,6 +211,9 @@ class compile_config
     /// \notes This allows detecting mismatches of configurations and parsers.
     virtual const char* do_get_name() const noexcept = 0;
 
+    /// \returns Whether to parse files as C rather than C++.
+    virtual bool do_use_c() const noexcept = 0;
+
     std::vector<std::string> flags_;
 };
 } // namespace cppast

include/cppast/libclang_parser.hpp

@@ -187,10 +187,13 @@ class libclang_compile_config final : public compile_config
         return "libclang";
     }
 
+    bool do_use_c() const noexcept override;
+
     std::string clang_binary_;
     bool        write_preprocessed_ : 1;
     bool        fast_preprocessing_ : 1;
     bool        remove_comments_in_macro_ : 1;
+    bool        use_c_              : 1;
 
     friend detail::libclang_compile_config_access;
 };

src/libclang/libclang_parser.cpp

@@ -82,7 +82,7 @@ libclang_compile_config::libclang_compile_config() : libclang_compile_config(CPP
 
 libclang_compile_config::libclang_compile_config(std::string clang_binary)
 : compile_config({}), write_preprocessed_(false), fast_preprocessing_(false),
-  remove_comments_in_macro_(false)
+  remove_comments_in_macro_(false), use_c_(false)
 {
     // set given clang binary
     set_clang_binary(clang_binary);
@@ -226,6 +226,11 @@ cppast::libclang_compile_config::libclang_compile_config(
     for (auto i = 0u; i != size; ++i)
     {
         auto cmd = clang_CompileCommands_getCommand(commands.get(), i);
+
+        // If ++ exists within the compiler name (e.g. clang++, g++, etc), use C++
+        std::string exe(clang_getCString(clang_CompileCommand_getArg(cmd, 0)));
+        use_c_ = (exe.find("++", 0) == std::string::npos);
+
         auto dir = detail::cxstring(clang_CompileCommand_getDirectory(cmd));
         parse_flags(cmd, [&](std::string flag, std::string args) {
             if (flag == "-I")
@@ -243,11 +248,21 @@ cppast::libclang_compile_config::libclang_compile_config(
                 add_flag(std::move(flag));
             }
             else if (flag == "-std")
-                // standard
+            {
+                use_c_ = (args.find("++") == std::string::npos);
                 add_flag(std::move(flag) + "=" + std::move(args));
+            }
             else if (flag == "-f")
                 // other options
                 add_flag(std::move(flag) + std::move(args));
+            else if (flag == "-x")
+            {
+                // language
+                if (args == "c")
+                    use_c_ = true;
+                else
+                    use_c_ = false;
+            }
         });
     }
 }
@@ -270,8 +285,9 @@ bool is_valid_binary(const std::string& binary)
 void add_default_include_dirs(libclang_compile_config& config)
 {
     std::string  verbose_output;
+    std::string  language = config.use_c() ? "-xc" : "-xc++";
     tpl::Process process(
-        detail::libclang_compile_config_access::clang_binary(config) + " -x c++ -v -", "",
+        detail::libclang_compile_config_access::clang_binary(config) + " " + language + " -v -", "",
         [](const char*, std::size_t) {},
         [&](const char* str, std::size_t n) { verbose_output.append(str, n); }, true);
     process.write("", 1);
@@ -424,6 +440,57 @@ void libclang_compile_config::do_set_flags(cpp_standard standard, compile_flags
                 add_flag("-std=c++2a");
             break;
         }
+        else
+            throw std::invalid_argument("c++2b is not yet supported for current version of clang");
+    case cpp_standard::c_89:
+        if (flags & compile_flag::gnu_extensions)
+            add_flag("-std=gnu89");
+        else
+            add_flag("-std=c89");
+        break;
+    case cpp_standard::c_99:
+        if (flags & compile_flag::gnu_extensions)
+            add_flag("-std=gnu99");
+        else
+            add_flag("-std=c99");
+        break;
+    case cpp_standard::c_11:
+        if (flags & compile_flag::gnu_extensions)
+            add_flag("-std=gnu11");
+        else
+            add_flag("-std=c11");
+        break;
+    case cpp_standard::c_17:
+        if (libclang_parser::libclang_minor_version() >= 45)
+        { // Corresponds to Clang version 6
+            if (flags & compile_flag::gnu_extensions)
+                add_flag("-std=gnu17");
+            else
+                add_flag("-std=c17");
+            break;
+        }
+        else
+            throw std::invalid_argument("c17 is not yet supported for current version of clang");
+    case cpp_standard::c_2x:
+        if (libclang_parser::libclang_minor_version() >= 59)
+        { // Corresponds to Clang version 9
+            if (flags & compile_flag::gnu_extensions)
+                add_flag("-std=gnu2x");
+            else
+                add_flag("-std=c2x");
+            break;
+        }
+        else
+            throw std::invalid_argument("c2x is not yet supported for current version of clang");
+    }
+
+    // Add language flag for C or C++
+    if (is_c_standard(standard)) {
+        add_flag("-xc");
+        use_c_ = true;
+    } else {
+        add_flag("-xc++");
+        use_c_ = false;
     }
 
     if (flags & compile_flag::ms_compatibility)
@@ -461,6 +528,11 @@ void libclang_compile_config::do_remove_macro_definition(std::string name)
     add_flag("-U" + std::move(name));
 }
 
+bool libclang_compile_config::do_use_c() const noexcept
+{
+    return use_c_;
+}
+
 type_safe::optional<libclang_compile_config> cppast::find_config_for(
     const libclang_compilation_database& database, std::string file_name)
 {
@@ -474,7 +546,7 @@ type_safe::optional<libclang_compile_config> cppast::find_config_for(
     if (database.has_config(file_name))
         return libclang_compile_config(database, std::move(file_name));
     static const char* extensions[]
-        = {".h", ".hpp", ".cpp", ".h++", ".c++", ".hxx", ".cxx", ".hh", ".cc", ".H", ".C"};
+        = {".h", ".hpp", ".cpp", ".h++", ".c++", ".hxx", ".cxx", ".hh", ".cc", ".H", ".C", ".c"};
     for (auto ext : extensions)
     {
         auto name = file_name + ext;
@@ -511,8 +583,8 @@ namespace
 std::vector<const char*> get_arguments(const libclang_compile_config& config)
 {
     std::vector<const char*> args
-        // TODO: Why? and Why?
-        = {"-x", "c++", "-I."}; // force C++ and enable current directory for include search
+        // TODO: Why?
+        = {"-I."}; // enable current directory for include search
     for (auto& flag : detail::libclang_compile_config_access::flags(config))
         args.push_back(flag.c_str());
     return args;

src/libclang/preprocessor.cpp

@@ -174,11 +174,12 @@ std::string diagnostics_flags()
 // get the command that returns all macros defined in the TU
 std::string get_macro_command(const libclang_compile_config& c, const char* full_path)
 {
-    // -x c++: force C++ as input language
+    // -xc/-xc++: force C or C++ as input language
     // -I.: add current working directory to include search path
     // -E: print preprocessor output
     // -dM: print macro definitions instead of preprocessed file
-    auto flags = std::string("-x c++ -I. -E -dM");
+    std::string language = c.use_c() ? "-xc" : "-xc++";
+    auto flags = language + " -I. -E -dM";
     flags += diagnostics_flags();
 
     std::string cmd(detail::libclang_compile_config_access::clang_binary(c) + " " + std::move(flags)
@@ -198,10 +199,11 @@ std::string get_macro_command(const libclang_compile_config& c, const char* full
 std::string get_preprocess_command(const libclang_compile_config& c, const char* full_path,
                                    const char* macro_file_path)
 {
-    // -x c++: force C++ as input language
+    // -xc/-xc++: force C or C++ as input language
     // -E: print preprocessor output
     // -dD: keep macros
-    auto flags = std::string("-x c++ -E -dD");
+    std::string language = c.use_c() ? "-xc" : "-xc++";
+    auto flags = language + " -E -dD";
 
     // -CC: keep comments, even in macro
     // -C: keep comments, but not in macro

test/parser.cpp

@@ -27,6 +27,11 @@ TEST_CASE("parse_files")
         {
             return "null";
         }
+
+        bool do_use_c() const noexcept override
+        {
+            return false;
+        }
     } config;
 
     class null_parser : public parser