Overhaul the AST representation of Objective-C message send

expressions, to improve source-location information, clarify the
actual receiver of the message, and pave the way for proper C++
support. The ObjCMessageExpr node represents four different kinds of
message sends in a single AST node:

  1) Send to a object instance described by an expression (e.g., [x method:5])
  2) Send to a class described by the class name (e.g., [NSString method:5])
  3) Send to a superclass class (e.g, [super method:5] in class method)
  4) Send to a superclass instance (e.g., [super method:5] in instance method)

Previously these four cases where tangled together. Now, they have
more distinct representations. Specific changes:

  1) Unchanged; the object instance is represented by an Expr*.

  2) Previously stored the ObjCInterfaceDecl* referring to the class
  receiving the message. Now stores a TypeSourceInfo* so that we know
  how the class was spelled. This both maintains typedef information
  and opens the door for more complicated C++ types (e.g., dependent
  types). There was an alternative, unused representation of these
  sends by naming the class via an IdentifierInfo *. In practice, we
  either had an ObjCInterfaceDecl *, from which we would get the
  IdentifierInfo *, or we fell into the case below...

  3) Previously represented by a class message whose IdentifierInfo *
  referred to "super". Sema and CodeGen would use isStr("super") to
  determine if they had a send to super. Now represented as a
  "class super" send, where we have both the location of the "super"
  keyword and the ObjCInterfaceDecl* of the superclass we're
  targetting (statically).

  4) Previously represented by an instance message whose receiver is a
  an ObjCSuperExpr, which Sema and CodeGen would check for via
  isa<ObjCSuperExpr>(). Now represented as an "instance super" send,
  where we have both the location of the "super" keyword and the
  ObjCInterfaceDecl* of the superclass we're targetting
  (statically). Note that ObjCSuperExpr only has one remaining use in
  the AST, which is for "super.prop" references.

The new representation of ObjCMessageExpr is 2 pointers smaller than
the old one, since it combines more storage. It also eliminates a leak
when we loaded message-send expressions from a precompiled header. The
representation also feels much cleaner to me; comments welcome!

This patch attempts to maintain the same semantics we previously had
with Objective-C message sends. In several places, there are massive
changes that boil down to simply replacing a nested-if structure such
as:

  if (message has a receiver expression) {
    // instance message
    if (isa<ObjCSuperExpr>(...)) {
     // send to super
    } else {
     // send to an object
   }
  } else {
    // class message
    if (name->isStr("super")) {
      // class send to super
    } else {
      // send to class
    }
  }

with a switch

  switch (E->getReceiverKind()) {
  case ObjCMessageExpr::SuperInstance: ...
  case ObjCMessageExpr::Instance: ...
  case ObjCMessageExpr::SuperClass: ...
  case ObjCMessageExpr::Class:...
  }

There are quite a few places (particularly in the checkers) where
send-to-super is effectively ignored. I've placed FIXMEs in most of
them, and attempted to address send-to-super in a reasonable way. This
could use some review.



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@101972 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 7 insertions, 5 deletions

diff --git a/lib/Checker/CallAndMessageChecker.cpp b/lib/Checker/CallAndMessageChecker.cpp
index ce9f26ec69..9d0dc33395 100644
--- a/lib/Checker/CallAndMessageChecker.cpp
+++ b/lib/Checker/CallAndMessageChecker.cpp
@@ -218,7 +218,8 @@ void CallAndMessageChecker::PreVisitObjCMessageExpr(CheckerContext &C,
 
   const GRState *state = C.getState();
 
-  if (const Expr *receiver = ME->getReceiver())
+  // FIXME: Handle 'super'?
+  if (const Expr *receiver = ME->getInstanceReceiver())
     if (state->getSVal(receiver).isUndef()) {
       if (ExplodedNode *N = C.GenerateSink()) {
         if (!BT_msg_undef)
@@ -265,10 +266,11 @@ void CallAndMessageChecker::EmitNilReceiverBug(CheckerContext &C,
      << ME->getType().getAsString() << "' that will be garbage";
 
   EnhancedBugReport *report = new EnhancedBugReport(*BT_msg_ret, os.str(), N);
-  const Expr *receiver = ME->getReceiver();
-  report->addRange(receiver->getSourceRange());
-  report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue,
-                            receiver);
+  if (const Expr *receiver = ME->getInstanceReceiver()) {
+    report->addRange(receiver->getSourceRange());
+    report->addVisitorCreator(bugreporter::registerTrackNullOrUndefValue,
+                              receiver);
+  }
   C.EmitReport(report);
 }