Re: [boost] Clang: Open-source C/C++ front end under development

From: Chris Lattner (clattner_at_[hidden])
Date: 2007-09-01 21:38:36

On Sep 1, 2007, at 6:32 PM, Andrew Sutton wrote:

>> I agree with Vladimir: my definition refactoring is as a behavior-
>> preserving transformation from one valid program to another.  Given
>> this, you really do need much of a compiler, but you also want highly
>> accurate source location information, information about macro
>> expansions, etc which compilers typically don't keep.  It's an
>> explicit goal for us to preserve that information and our solutions
>> seem to work well for us so far.
>
> To start with, your definition of refactoring is incorrect - it
> simply preserves the external behavior of a program.

I carefully said it was "my definition" because I'm aware there are  
multiple different interpretations.  Why do you consider your  
definition to be the 'right' one? :)

> I would also
> point out that in order to ensure that a program is correct it first
> has to be preprocessed, and parsed. Something as simple as renaming a
> function - which is a well-known refactoring - requires none of that.

Actually, you're wrong.  C and C++ require token pasting and escaped  
newline splicing to happen - and they certainly can occur in  
identifiers.  That is, unless you're willing to break some correct  
code, various hacks like using sed can sometimes work... be careful  
of scoping issues though, particularly when macros can expand into  
{'s :)

> The complexity of the refactoring determines the amount of
> information needed - whether or not you actually need a fully correct
> AST all the time - I doubt it.

Certainly, it obviously depends on the transformation.

-Chris