[analyzer] Teach CallEvent about C++17 aligned operator new().

In C++17, when class C has large alignment value, a special case of
overload resolution rule kicks in for expression new C that causes the aligned
version of operator new() to be called. The aligned new has two arguments:
size and alignment. However, the new-expression has only one "argument":
the construct-expression for C(). This causes a false positive in
core.CallAndMessage's check for matching number of arguments and number
of parameters.

Update CXXAllocatorCall, which is a CallEvent sub-class for operator new calls
within new-expressions, so that the number of arguments always matched
the number of parameters.

rdar://problem/44738501

Differential Revision: https://reviews.llvm.org/D52957


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@344539 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 16 insertions, 3 deletions

diff --git a/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h b/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
index 4c50eafbde..9430beed74 100644
--- a/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
+++ b/include/clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h
@@ -921,15 +921,28 @@ public:
     return getOriginExpr()->getOperatorNew();
   }
 
+  // Size and maybe implicit alignment in C++17. Instead of size, the AST
+  // contains the construct-expression. Alignment is always hidden.
+  // We pretend that argument 0 is size and argument 1 is alignment (if passed
+  // implicitly) and the rest are placement args. This makes sure that the
+  // number of arguments is always the same as the number of parameters.
+  unsigned getNumImplicitArgs() const {
+    return getOriginExpr()->passAlignment() ? 2 : 1;
+  }
+
   unsigned getNumArgs() const override {
-    return getOriginExpr()->getNumPlacementArgs() + 1;
+    return getOriginExpr()->getNumPlacementArgs() + getNumImplicitArgs();
   }
 
   const Expr *getArgExpr(unsigned Index) const override {
     // The first argument of an allocator call is the size of the allocation.
-    if (Index == 0)
+    if (Index < getNumImplicitArgs())
       return nullptr;
-    return getOriginExpr()->getPlacementArg(Index - 1);
+    return getOriginExpr()->getPlacementArg(Index - getNumImplicitArgs());
+  }
+
+  const Expr *getPlacementArgExpr(unsigned Index) const {
+    return getOriginExpr()->getPlacementArg(Index);
   }
 
   Kind getKind() const override { return CE_CXXAllocator; }