[PATCH] D154479: [clang][dataflow] Bug fix: `BuiltinFnToFnPtr` cast does not produce a pointer.

[Martin Böhme via Phabricator via cfe-commits]

mboehme created this revision.
Herald added subscribers: martong, xazax.hun.
Herald added a reviewer: NoQ.
Herald added a project: All.
mboehme requested review of this revision.
Herald added a project: clang.
Herald added a subscriber: cfe-commits.

See comments in the code for details.


Repository:
  rG LLVM Github Monorepo

https://reviews.llvm.org/D154479

Files:
  clang/lib/Analysis/FlowSensitive/Transfer.cpp
  clang/unittests/Analysis/FlowSensitive/TransferTest.cpp


Index: clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
===================================================================
--- clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
+++ clang/unittests/Analysis/FlowSensitive/TransferTest.cpp
@@ -5449,8 +5449,8 @@
       });
 }
 
-// Check that the pointer that a builtin function decays to is associated with
-// a value.
+// Check that a builtin function is not associated with a value. (It's only
+// possible to call builtin functions directly, not take their address.)
 TEST(TransferTest, BuiltinFunctionModeled) {
   std::string Code = R"(
     void target() {
@@ -5478,7 +5478,7 @@
                   ASTCtx));
 
         ASSERT_THAT(ImplicitCast, NotNull());
-        EXPECT_THAT(Env.getValueStrict(*ImplicitCast), NotNull());
+        EXPECT_THAT(Env.getValueStrict(*ImplicitCast), IsNull());
       });
 }
 
Index: clang/lib/Analysis/FlowSensitive/Transfer.cpp
===================================================================
--- clang/lib/Analysis/FlowSensitive/Transfer.cpp
+++ clang/lib/Analysis/FlowSensitive/Transfer.cpp
@@ -419,8 +419,7 @@
       // FIXME: Implement pointers to members. For now, don't associate a value
       // with this expression.
       break;
-    case CK_FunctionToPointerDecay:
-    case CK_BuiltinFnToFnPtr: {
+    case CK_FunctionToPointerDecay: {
       StorageLocation *PointeeLoc =
           Env.getStorageLocation(*SubExpr, SkipPast::Reference);
       if (PointeeLoc == nullptr)
@@ -432,6 +431,12 @@
       Env.setValue(PointerLoc, PointerVal);
       break;
     }
+    case CK_BuiltinFnToFnPtr:
+      // Despite its name, the result type of `BuiltinFnToFnPtr` is a function,
+      // not a function pointer. In addition, builtin functions can only be
+      // called directly; it is not legal to take their address. We therefore
+      // don't need to create a value or storage location for them.
+      break;
     default:
       break;
     }


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