clang can't parse my .h file standalone

I'm using python binding of libclang but I think this problem is caused by libclang not by python binding.

I have a header object.h

#ifndef OBJECT_H
#define OBJECT_H

class Object {
public:
  int run();
};

#endif

And a implementation object.cpp

#include "object.h"

int Object::run() {
  int a = 0;
  return a*a;
}

If I visit AST of the translation unit of object.h , the last AST node is VAR_DECL class Object and that's it. It won't visit public:... part. If I use clang to check syntax directly is would complain about my header file is wrong.

$ clang -Xclang -ast-dump -fsyntax-only object/object.h
object/object.h:4:1: error: unknown type name 'class'
class Object {
^
object/object.h:4:13: error: expected ';' after top level declarator
class Object {
            ^
            ;
TranslationUnitDecl 0x7f816102d2d0 <<invalid sloc>>
|-TypedefDecl 0x7f816102d7d0 <<invalid sloc>> __int128_t '__int128'
|-TypedefDecl 0x7f816102d830 <<invalid sloc>> __uint128_t 'unsigned __int128'
|-TypedefDecl 0x7f816102db80 <<invalid sloc>> __builtin_va_list '__va_list_tag [1]'
`-VarDecl 0x7f816102dbf0 <object/object.h:4:1, col:7> Object 'int' invalid
2 errors generated.

If I use clang to dump ast of object.cpp , I won't have that error.

$ clang -Xclang -ast-dump -fsyntax-only object/object.cpp
TranslationUnitDecl 0x7fc6230302d0 <<invalid sloc>>
|-TypedefDecl 0x7fc623030810 <<invalid sloc>> __int128_t '__int128'
|-TypedefDecl 0x7fc623030870 <<invalid sloc>> __uint128_t 'unsigned __int128'
|-TypedefDecl 0x7fc623030c30 <<invalid sloc>> __builtin_va_list '__va_list_tag [1]'
|-CXXRecordDecl 0x7fc623030c80 <object/object.h:4:1, line:7:1> class Object definition
| |-CXXRecordDecl 0x7fc623030d90 <line:4:1, col:7> class Object
| |-AccessSpecDecl 0x7fc623030e20 <line:5:1, col:7> public
| `-CXXMethodDecl 0x7fc623030ea0 <line:6:3, col:11> run 'int (void)'
`-CXXMethodDecl 0x7fc62307be10 parent 0x7fc623030c80 prev 0x7fc623030ea0 <object/object.cpp:3:1, line:6:1> run 'int (void)'
  `-CompoundStmt 0x7fc62307c058 <line:3:19, line:6:1>
    |-DeclStmt 0x7fc62307bf78 <line:4:3, col:12>
    | `-VarDecl 0x7fc62307bf00 <col:3, col:11> a 'int'
    |   `-IntegerLiteral 0x7fc62307bf58 <col:11> 'int' 0
    `-ReturnStmt 0x7fc62307c038 <line:5:3, col:12>
      `-BinaryOperator 0x7fc62307c010 <col:10, col:12> 'int' '*'
        |-ImplicitCastExpr 0x7fc62307bfe0 <col:10> 'int' <LValueToRValue>
        | `-DeclRefExpr 0x7fc62307bf90 <col:10> 'int' lvalue Var 0x7fc62307bf00 'a' 'int'
        `-ImplicitCastExpr 0x7fc62307bff8 <col:12> 'int' <LValueToRValue>
          `-DeclRefExpr 0x7fc62307bfb8 <col:12> 'int' lvalue Var 0x7fc62307bf00 'a' 'int'

It seems like clang combine object.h object.cpp together then do the parsing. If that's so, how do I get the ast node of Object in thrid line of object.cpp int Object::run() { ? Is there a ast node for that?

It also confuses me a lot like when I visit the run() method in object.cpp , it will say current location is in object.cpp but the extent is in object.h . What does the extent mean exactly? Any easier tutorial documents other than libclang API document?

Clang doesn't know that you have C++ code in your .h file. By default, it treats a .h file as plain C. When you run clang on your .cpp file, it knows that it's parsing C++.

There are two ways to fix this.

clang -x c++ -Xclang -ast-dump -fsyntax-only object/object.h

mv object/object.h object/object.hpp
clang -Xclang -ast-dump -fsyntax-only object/object.hpp

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