[cfe-dev] Function body type

[Douglas Gregor]

On Apr 26, 2009, at 8:19 AM, Sebastian Redl wrote:

> Hi,
>
> Small problem: the type of a function's body is currently  
> CompoundStmt.
> However, in C++ we have function-try-blocks:
>
> void f() try {
>  // things that could throw
> } catch(something) {
>  // ...
> } catch(...) {
>  // ...
> }
>
> The obvious solution here is to change FunctionDecl so that its body  
> can
> be either a CompoundStmt or a CXXTryStmt (by having getBody() return
> either a Stmt* or a PointerVariant). However, this change is quite
> disrupting to many, many components.

I think using Stmt* is perfectly reasonable. I am not at all worried  
about this change touching many components; it's a mechanical  
transformation that is unlikely to break anything and it is the right  
thing to do.

It probably makes sense to add a

   CompoundStmt *getCompoundBody(ASTContext &Context, const  
FunctionDecl *&Definition) {
     return dyn_cast_or_null<CompoundStmt>(getBody(Context,  
Definition));
   }

so that we've encapsulated the dyn_cast_or_null into a single place.

> The alternative is to represent such functions as if they were  
> written as
>
> void f() {
>  try { .... } ...
> }
>
> There exists a difference in semantics for constructors and  
> destructors
> only (where a function-try-block covers base and member
> initializers/destructors, whereas a try-block does not), which could  
> be
> stored in a flag in those functions. But I don't like this workaround.

I don't like this workaround, either. We want the AST to describe the  
syntax and semantics naturally, and this kind of flag would really  
confuse the issue.

	- Doug