[cfe-dev] AST transformations

[Reid Kleckner]

On Thu, Mar 10, 2011 at 2:43 PM, Vassil Vassilev
<vasil.georgiev.vasilev at cern.ch> wrote:
> Hi,
> On 10.3.2011 г. 18:07, Reid Kleckner wrote:
>>
>> True.  I've been assured that mutating the AST is very difficult to do
>> correctly, but I don't fully understand why.  Perhaps it would be a
>> good idea to write up an FAQ explaining why clang doesn't support it,
>> with an example of why a simple local modification can break other
>> parts of the AST (ie switching the cmp condition).
>>> RewriteObjC class uses ASTConsumer; however, looking at the source
>>> it's not immediately clear to me whether it is transforming the AST or
>>> just inserting extra declarations/statements/etc. at the source level.
>> The recommended approach for transforming the program source is to
>> analyze the AST and use the source locations in the AST to make
>> textual, source-level edits.
> This part I didn't understand. You mean finding the source location of
> the AST nodes, inserting and reparsing?

I don't know much about the objc rewriter, but the way that fixits
work is they emit a diagnostic that has a symbolic textual operation
on it, something like insert, replace, or delete text at a given
source range.  There is no reparsing.

Reid