[cfe-dev] AST-dump

Tue May 28 02:07:01 PDT 2013

> That seems like an approach that works. I don't know that there's a different common property. Why's the default constructor different from the copy constructor here?
> 
First of all, sorry but I made a mistake in the example:

class A{
1.   A(){...}
2.   A(int a){...}
3.   A(const A& a){... ...}
};

What I mean is that I need to find if there is at least one constructor that explicitly overloads the default constructor so that if I delete the default constructor the compiler won't provide the default constructor. So, my question was totally erroneous as the copy constructor does overload the default constructor if provided, but I don't want to take it into account if it wasn't explicitly provided.

A better question is: which are the kind of constructors that the compiler provides if no constructors are explicitly supplied? Only the default and the copy constructor (in some situations)?

If "unless(allOf(... ...))" is the best solution, could someone enumerate the kind of constructors I must to indicate in that matcher?

> I'd suggest to not use ast-dump-xml any more. It's basically deprecated, and hopefully it'll be removed soon. -ast-dump gives you all the information (and more).
> 
Ok, I didn't know it.

> ... you can see that one is the default constructor and the other one is the copy constructor. If you just put "G g;" into the code instead of the second class, you'll also see that a simple use of G already triggers the copy constructor to appear. Others are probably better able to explain exactly when a copy constructor is created.
> 
Further information will be well received.

Regards,

Pedro.

El dia 27 may 2013 12:24, Manuel Klimek <klimek at google.com> escribió:
> Hi Pedro,
> first, please always send those mails also to cfe-dev. There are people who are much more knowledgable about the AST on that list, and you'll often get better answers faster that way :)
> On Mon, May 27, 2013 at 10:00 AM, Pedro Delgado Perez <pedro.delgado at uca.es [ mailto:pedro.delgado at uca.es ]> wrote:
> 
> 
> 
> Sorry Manuel, but I prefer to ask you all the things I don't know before you reply me:
> 
> How do I know that a CXXConstructorDecl is a "simple" constructor of a class. I mean, I want to find all the constructors in a class, but not the copy, the move or things like this constructors. I'm not able to find this in the documentation. To clarify this, I'm going to put an example:
> 
> class A{
> 1.   A(){...}
> 2.   A(int a){...}
> 3.   A(const &a){... ...}
> };
> 
> I want to look only for 1 and 2 and not for 3 when I ask:
> recordDecl(hasMethod(constructDecl(...)));
> 
> What can I do? Do I have to write "unless(allOf(isCopyConstructor(), isMoveConstructor()...))" for each type of existing constructors?
> 
That seems like an approach that works. I don't know that there's a different common property. Why's the default constructor different from the copy constructor here?

Thanks,

Pedro.

Hi Manuel,

I would like to ask you something about the AST built by Clang if you don't mind.  I've just have a look at your video  of introduction to Clang AST (By the way, nice tutorial!) and I think that you may have an answer for my trouble.

Look, I was trying to look for classes that had only the default constructor through ASTMatchers. Well, I tested my matcher with the next classes:

class G{
public:
    G():a(1){}
    int a;
    virtual int ma(int arg);
};

class L: public G{
    public:
        L(){v = 1;}
        int b;
        int h;
        virtual int ma(int arg);
    private:
        int v;
        int f();
};

My matcher only retrieved the class 'L' and not the 'G'. I was wondering what would be the problem when I had a look to the ast-dump-xml option:

I'd suggest to not use ast-dump-xml any more. It's basically deprecated, and hopefully it'll be removed soon. -ast-dump gives you all the information (and more).

 <CXXRecord ptr="0xd695f30" name="G" typeptr="0xd695f80">
 <CXXRecord ptr="0xd695fd0" name="G" typeptr="0xd695f80"/>
 <AccessSpec ptr="0xd696020" access="public"/>
 <CXXConstructor used="1" ptr="0xd696080" name="G" prototype="true">
  <FunctionProtoType ptr="0xd696050" canonical="0xd696050">
  <BuiltinType ptr="0xd695c40" canonical="0xd695c40"/>
  <parameters/>
  </FunctionProtoType>
  <Stmt>
CompoundStmt 0xd696450 <tst.cpp:7:10, col:11>
  </Stmt>
 </CXXConstructor>

....

<CXXConstructor ptr="0xd6aefc0" name="G" prototype="true" inline="true">
  <FunctionProtoType ptr="0xd6af050" canonical="0xd6af030" exception_spec="unevaluated">
  <BuiltinType ptr="0xd695c40" canonical="0xd695c40"/>
  <parameters>
   <LValueReferenceType ptr="0xd696240" canonical="0xd696240">
   <QualType const="true">
    <RecordType ptr="0xd695f80" canonical="0xd695f80">
    <CXXRecord ref="0xd695f30"/>
    </RecordType>
   </QualType>
   </LValueReferenceType>
  </parameters>
  </FunctionProtoType>
  <ParmVar ptr="0xd6af070" name="" initstyle="c">
  <LValueReferenceType ptr="0xd696240" canonical="0xd696240">
   <QualType const="true">
   <RecordType ptr="0xd695f80" canonical="0xd695f80">
    <CXXRecord ref="0xd695f30"/>
   </RecordType>
   </QualType>
  </LValueReferenceType>
  </ParmVar>
 </CXXConstructor>
 </CXXRecord>

Why class 'G' has two constructors? If I change the test program in order that class 'L' doesn't inherits from class 'G', this doesn't happen (class 'G' only has one constructor in the ast-dump-xml) Could you lend me a hand?

If you look at -ast-dump:

$ clang -cc1 -ast-dump t4.cc
<snip>
|-CXXRecordDecl 0x37faf80 <t4.cc:1:1, line:6:1> class G
<snip>
| |-CXXConstructorDecl 0x37fb1c0 <line:3:3, col:15> G 'void (void)'
| | |-CXXCtorInitializer Field 0x37fb290 'a' 'int'
| | | |-IntegerLiteral 0x382d018 <col:11> 'int' 1
| | `-CompoundStmt 0x382d0a0 <col:14, col:15>
<snip>
| `-CXXConstructorDecl 0x382da70 <col:7> G 'void (const class G &)' inline
|  `-ParmVarDecl 0x382f820 <col:7> 'const class G &'
<snip>
... you can see that one is the default constructor and the other one is the copy constructor. If you just put "G g;" into the code instead of the second class, you'll also see that a simple use of G already triggers the copy constructor to appear. Others are probably better able to explain exactly when a copy constructor is created.
cheers,
/Manuel
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