[clang][dataflow]Propagate the result object location for CXXDefaultInitExpr. (#98490)

These are not "original initializers"; the single node underneath
represents the initializing node.

Author: bazuzi

clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp

@@ -15,6 +15,7 @@
 #include "clang/Analysis/FlowSensitive/DataflowEnvironment.h"
 #include "clang/AST/Decl.h"
 #include "clang/AST/DeclCXX.h"
+#include "clang/AST/ExprCXX.h"
 #include "clang/AST/RecursiveASTVisitor.h"
 #include "clang/AST/Stmt.h"
 #include "clang/AST/Type.h"
@@ -414,8 +415,8 @@ class ResultObjectVisitor : public AnalysisASTVisitor<ResultObjectVisitor> {
     // lowest-level AST node that initializes a given object, and nothing
     // below them can initialize the same object (or part of it).
     if (isa<CXXConstructExpr>(E) || isa<CallExpr>(E) || isa<LambdaExpr>(E) ||
-        isa<CXXDefaultArgExpr>(E) || isa<CXXDefaultInitExpr>(E) ||
-        isa<CXXStdInitializerListExpr>(E) || isa<AtomicExpr>(E) ||
+        isa<CXXDefaultArgExpr>(E) || isa<CXXStdInitializerListExpr>(E) ||
+        isa<AtomicExpr>(E) ||
         // We treat `BuiltinBitCastExpr` as an "original initializer" too as
         // it may not even be casting from a record type -- and even if it is,
         // the two objects are in general of unrelated type.
@@ -463,6 +464,11 @@ class ResultObjectVisitor : public AnalysisASTVisitor<ResultObjectVisitor> {
       return;
     }
 
+    if (auto *DIE = dyn_cast<CXXDefaultInitExpr>(E)) {
+      PropagateResultObject(DIE->getExpr(), Loc);
+      return;
+    }
+
     // All other expression nodes that propagate a record prvalue should have
     // exactly one child.
     SmallVector<Stmt *, 1> Children(E->child_begin(), E->child_end());

clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp

@@ -21,6 +21,7 @@
 #include "gmock/gmock.h"
 #include "gtest/gtest.h"
 #include <memory>
+#include <string>
 
 namespace {
 
@@ -405,6 +406,42 @@ TEST_F(EnvironmentTest,
               Contains(Member));
 }
 
+// This is a repro of a failure case seen in the wild.
+TEST_F(EnvironmentTest, CXXDefaultInitExprResultObjIsWrappedExprResultObj) {
+  using namespace ast_matchers;
+
+  std::string Code = R"cc(
+      struct Inner {};
+
+      struct S {
+        S() {}
+
+        Inner i = {};
+      };
+  )cc";
+
+  auto Unit =
+      tooling::buildASTFromCodeWithArgs(Code, {"-fsyntax-only", "-std=c++11"});
+  auto &Context = Unit->getASTContext();
+
+  ASSERT_EQ(Context.getDiagnostics().getClient()->getNumErrors(), 0U);
+
+  auto Results =
+      match(cxxConstructorDecl(
+                hasAnyConstructorInitializer(cxxCtorInitializer(
+                    withInitializer(expr().bind("default_init_expr")))))
+                .bind("ctor"),
+            Context);
+  const auto *Constructor = selectFirst<CXXConstructorDecl>("ctor", Results);
+  const auto *DefaultInit =
+      selectFirst<CXXDefaultInitExpr>("default_init_expr", Results);
+
+  Environment Env(DAContext, *Constructor);
+  Env.initialize();
+  EXPECT_EQ(&Env.getResultObjectLocation(*DefaultInit),
+            &Env.getResultObjectLocation(*DefaultInit->getExpr()));
+}
+
 TEST_F(EnvironmentTest, Stmt) {
   using namespace ast_matchers;