[cfe-dev] TreeTransform and Clang

[Vassil Vassilev]

On Sat, 2010-08-07 at 13:47 +0200, Douglas Gregor wrote:
> On Aug 7, 2010, at 9:28 AM, Vassil Vassilev wrote:
> 
> > Hello,
> >  Hm, Is the error handling in the semantic analysis, too?
> 
> Yes.
> 
> >  I need the following
> >  For example (I am skipping the pointers and other ugly things that
> > made it less readable):
> > 
> >  funtion F(int x, float y,string z) {
> >     int i = objX.GetValue(x);  //compile time object and method
> > invocation
> >     TFile t = new TFile("MyFile.hhh");  //here goes the interpreter,but
> > it needs addresses of the variables from the compiler
> >     i = t.DoSomething(i, x, y, z);
> >     Console.WriteLine(i.ToString());
> >  }
> > 
> >  Here the semantic analyzer should say undeclared variable and so on. 
> 
> Yes, it will.
> 
> >  Before that happens I want to change the AST and to convert it in something like:
> > 
> >  funtion F(int x, float y,string z) {      
> >     int i = objX->GetValue(x);  //compile time object and method invocation      
> >     TFile t = new TFile("MyFile.hhh");  //here goes the interpreter,but it needs addresses of the variables from the compiler      
> >     Context c = new Context();
> >     c.AddVariable(i.GetDeclaration()) ; //here we should use some kind of  reflection or we can insert just the variable address and the proper mapping.   
> >     c.AddArgument(x.GetDeclaration());
> >     ...
> >     Interpreter.Interpret("t->DoSomething(i,x,y,z)", c);
> >     i = t.DoSomething(i, x, y, z);
> >     Console.WriteLine(i.ToString());   
> > } 
> > 
> >  I know I can modify the Sema and/or put something in the symbol table
> > to achieve the goal but I am looking for more elegant solution.
> 
> The right way to do this would be to augment Sema's name-lookup facilities, so that your application gets a chance to provide symbols when no other symbols of the same name work. One way to do this is to create your own ExternalASTSource, and override FindExternalVisibleDeclsByName to add those symbols. If I remember correctly, LLDB does this.
I understand. But I want only to replace one node of the AST with
another. I don't need to exchange external symbol names and so on (at
least for now). Is it possible to hook somewhere before the error
handling and substitute the ExpressionStatement (i = t.DoSomething(i, x,
y, z);) With new BlockStatement or several ExpressionStatements. Or in
case of error AST is not built (which is strange for me because it
wouldn't be flexible for complex transformations...).

> 
> > I know
> > that probably I can make second pass of the invalid AST but it is not
> > the most efficient way of solving the problem. 
> 
> You won't be able to make a second pass over the invalid AST; there isn't enough information left to produce a reasonable AST.
> 
> 	- Doug