[cfe-dev] Proposal to fix issue 7715

[Douglas Gregor]

On Sep 22, 2010, at 10:08 AM, Manuel Klimek wrote:

> On Mon, Sep 20, 2010 at 8:28 PM, Douglas Gregor <dgregor at apple.com> wrote:
>> 
>> On Sep 14, 2010, at 7:39 AM, Manuel Klimek wrote:
>> 
>>> Hi,
>>> 
>>> I came up with a solution to http://llvm.org/bugs/show_bug.cgi?id=7715
>>> (clang++ gives wrong error about default argument in kdatetime.h), as
>>> talked about on IRC. It was a little more complicated than
>>> anticipated, as we need to keep the stack of scopes correct.
>>> 
>>> I would like to get some feedback on the general direction /
>>> implementation of this patch. If we agree this is the way to go, I'd
>>> comment it more thoroughly and add some more regression tests.
>> 
>> I like the general direction; there are a few comments below. Obviously, more comments and regression tests would be greatly appreciated!
>> 
>>> I tried
>>> to keep the diff as small as possible, but my gut feeling would also
>>> lead me to put more stuff into the classes as opposed to having
>>> everything as methods on Parser. Not sure though.
>> 
>> I'd rather keep the parsing and Sema-invoking code in the parser itself, although I admit it's mostly an aesthetic argument and it's not a strong preference.
> 
> I trust your gut-feeling then ;)
> 
>> A few small comments:
>> 
>> diff --git a/include/clang/Parse/Parser.h b/include/clang/Parse/Parser.h
>> index a7dab1e..422adce 100644
>> --- a/include/clang/Parse/Parser.h
>> +++ b/include/clang/Parse/Parser.h
>> @@ -552,7 +552,30 @@ private:
>>   //===--------------------------------------------------------------------===//
>>   // Lexing and parsing of C++ inline methods.
>> 
>> -  struct LexedMethod {
>> +  struct ParsingClass;
>> +
>> +  class LateParsedDeclaration {
>> +  public:
>> +    virtual ~LateParsedDeclaration();
>> +    virtual void ParseLexedDefaultArguments();
>> +    virtual void ParseLexedMethodDefs();
>> +  };
>> 
>> I think the name ParseLexedDefaultArguments() is misleading, because default arguments aren't the only kind of thing that is delayed. C++ [class.mem]p1 also mentions function bodies (which we handle separately) and exception-specifications (which we don't handle)... the latter is why I'd prefer to keep a more generic name like "ParseLexedMethodDeclarations()".
> 
> While trying to comment that part I got pretty confused by what you
> write. In the C++ standard I didn't find anything in [class.mem]p1
> that mentions function bodies (am I reading the wrong version?), but I
> find that in [class.mem]p2 it talks about "function bodies, default
> arguments and constructor ctor-initializers", where I'd expect
> ctor-initializers to be basically handled the same as function bodies.
> Where do exception specifications fall into all this?

I was looking at the latest draft for the C++0x standard, where the contents of the C++98/03 [class.mem]p2 have moved into C++0x [class.mem]p1, and it now explicitly mentions exception-specifications as well as function bodies, default arguments, and (the C++0x extension) initializers for non-static data members.

> I called the methods ParseLexedDefaultArguments and
> ParseLexedMethodDefs as the function bodies must be parsed in a phase
> after all default arguments were parsed, since as far as I understand
> it the default arguments can always be used in the function bodies.
> I'd assume that anything else would be basically handled in a
> different phase, too.

I was thinking that exception-specifications could be handled at the same time as default arguments, so that we do the initialization in source order.

> The interface is called LateParsedDeclaration (perhaps wanting a
> better name), as all the late parsed stuff is always combined with a
> method declaration, as far as I understood it.

Eventually, we'll have non-static data member initializers, but for now it's just method declarations. 

	- Doug