[llvm-commits] [llvm] r78424 - /llvm/trunk/include/llvm/Support/Casting.h

[Argiris Kirtzidis]

Author: akirtzidis
Date: Fri Aug  7 17:49:24 2009
New Revision: 78424

URL: http://llvm.org/viewvc/llvm-project?rev=78424&view=rev
Log:
Modifications to dyn_cast/cast to make them work for objects too, instead of only pointers.

The use case is if you have a wrapper class:

class Base {
  void *Ptr;
public:
  Base() : Ptr(0) { }
  operator bool() const { return Ptr; }
....
}

and sub-wrappers that have exactly the same size:

class Sub : public Base {
public:
...
static bool classof(const Base*);
}

and in the code you would do:

void f(Base b) {
  Sub sub = dyn_cast<Sub>(b);
  if (sub) {
    ....
  }
}


Modified:
    llvm/trunk/include/llvm/Support/Casting.h

Modified: llvm/trunk/include/llvm/Support/Casting.h
URL: http://llvm.org/viewvc/llvm-project/llvm/trunk/include/llvm/Support/Casting.h?rev=78424&r1=78423&r2=78424&view=diff

==============================================================================
--- llvm/trunk/include/llvm/Support/Casting.h (original)
+++ llvm/trunk/include/llvm/Support/Casting.h Fri Aug  7 17:49:24 2009
@@ -205,8 +205,9 @@
 // accepted.
 //
 template <class X, class Y>
-inline typename cast_retty<X, Y*>::ret_type cast_or_null(Y *Val) {
-  if (Val == 0) return 0;
+inline typename cast_retty<X, Y>::ret_type cast_or_null(const Y &Val) {
+  typedef typename cast_retty<X, Y>::ret_type ret_type;
+  if (!Val) return ret_type();
   assert(isa<X>(Val) && "cast_or_null<Ty>() argument of incompatible type!");
   return cast<X>(Val);
 }
@@ -222,7 +223,8 @@
 
 template <class X, class Y>
 inline typename cast_retty<X, Y>::ret_type dyn_cast(const Y &Val) {
-  return isa<X>(Val) ? cast<X, Y>(Val) : 0;
+  typedef typename cast_retty<X, Y>::ret_type ret_type;
+  return isa<X>(Val) ? cast<X, Y>(Val) : (ret_type)ret_type();
 }
 
 // dyn_cast_or_null<X> - Functionally identical to dyn_cast, except that a null
@@ -230,7 +232,8 @@
 //
 template <class X, class Y>
 inline typename cast_retty<X, Y>::ret_type dyn_cast_or_null(const Y &Val) {
-  return (Val && isa<X>(Val)) ? cast<X, Y>(Val) : 0;
+  typedef typename cast_retty<X, Y>::ret_type ret_type;
+  return (Val && isa<X>(Val)) ? cast<X, Y>(Val) : (ret_type)ret_type();
 }