[clang] [clang][dataflow] Retrieve members from accessors called using member… (PR #73978)

[Samira Bazuzi via cfe-commits]

https://github.com/bazuzi updated https://github.com/llvm/llvm-project/pull/73978

>From aab1069636896c4a8289545ba01d2fdf4f1715c0 Mon Sep 17 00:00:00 2001
From: Samira Bazuzi <bazuzi at google.com>
Date: Thu, 30 Nov 2023 14:18:04 -0500
Subject: [PATCH 1/2] [clang][dataflow] Retrieve members from accessors called
 using member pointers.

getMethodDecl does not handle pointers to members and returns nullptr.
---
 .../FlowSensitive/DataflowEnvironment.cpp     |  5 +-
 .../FlowSensitive/DataflowEnvironmentTest.cpp | 50 +++++++++++++++++++
 2 files changed, 53 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
index 525ab188b01b8aa..5a37fa0f02f5d21 100644
--- a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
+++ b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
@@ -300,9 +300,10 @@ static void insertIfFunction(const Decl &D,
 }
 
 static MemberExpr *getMemberForAccessor(const CXXMemberCallExpr &C) {
-  if (!C.getMethodDecl())
+  const auto *MethodDecl = dyn_cast_or_null<CXXMethodDecl>(C.getCalleeDecl());
+  if (!MethodDecl)
     return nullptr;
-  auto *Body = dyn_cast_or_null<CompoundStmt>(C.getMethodDecl()->getBody());
+  auto *Body = dyn_cast_or_null<CompoundStmt>(MethodDecl->getBody());
   if (!Body || Body->size() != 1)
     return nullptr;
   if (auto *RS = dyn_cast<ReturnStmt>(*Body->body_begin()))
diff --git a/clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp b/clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp
index ff6cbec5d20b744..55fb6549621737a 100644
--- a/clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp
+++ b/clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp
@@ -306,6 +306,56 @@ TEST_F(EnvironmentTest, InitGlobalVarsConstructor) {
   EXPECT_THAT(Env.getValue(*Var), NotNull());
 }
 
+// Pointers to Members are a tricky case of accessor calls, complicated further
+// when using templates where the pointer to the member is a template argument.
+// This is a repro of a failure case seen in the wild.
+TEST_F(EnvironmentTest,
+       ModelMemberForAccessorUsingMethodPointerThroughTemplate) {
+  using namespace ast_matchers;
+
+  std::string Code = R"cc(
+      struct S {
+        int accessor() {return member;}
+
+        int member = 0;
+      };
+
+      template <auto method>
+      int Target(S* S) {
+        return (S->*method)();
+      }
+
+     // We want to analyze the instantiation of Target for the accessor.
+     int Instantiator () {S S; return Target<&S::accessor>(&S); }
+  )cc";
+
+  auto Unit =
+      // C++17 for the simplifying use of auto in the template declaration.
+      tooling::buildASTFromCodeWithArgs(Code, {"-fsyntax-only", "-std=c++17"});
+  auto &Context = Unit->getASTContext();
+
+  ASSERT_EQ(Context.getDiagnostics().getClient()->getNumErrors(), 0U);
+
+  auto Results = match(
+      decl(anyOf(functionDecl(hasName("Target"), isTemplateInstantiation())
+                     .bind("target"),
+                 fieldDecl(hasName("member")).bind("member"),
+                 recordDecl(hasName("S")).bind("struct"))),
+      Context);
+  const auto *Fun = selectFirst<FunctionDecl>("target", Results);
+  const auto *Struct = selectFirst<RecordDecl>("struct", Results);
+  const auto *Member = selectFirst<FieldDecl>("member", Results);
+  ASSERT_THAT(Fun, NotNull());
+  ASSERT_THAT(Struct, NotNull());
+  ASSERT_THAT(Member, NotNull());
+
+  // Verify that `member` is modeled for `S` when we analyze
+  // `Target<&S::accessor>`.
+  Environment Env(DAContext, *Fun);
+  EXPECT_THAT(DAContext.getModeledFields(QualType(Struct->getTypeForDecl(), 0)),
+              Contains(Member));
+}
+
 TEST_F(EnvironmentTest, RefreshRecordValue) {
   using namespace ast_matchers;
 

>From 120bdd51496dd69c601181bccae072effb547920 Mon Sep 17 00:00:00 2001
From: Samira Bazuzi <bazuzi at google.com>
Date: Fri, 1 Dec 2023 10:33:54 -0500
Subject: [PATCH 2/2] Add missing using declaration to test.

And add comment.
---
 clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp         | 1 +
 .../unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp | 1 +
 2 files changed, 2 insertions(+)

diff --git a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
index 5a37fa0f02f5d21..0b962bff4c183bf 100644
--- a/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
+++ b/clang/lib/Analysis/FlowSensitive/DataflowEnvironment.cpp
@@ -300,6 +300,7 @@ static void insertIfFunction(const Decl &D,
 }
 
 static MemberExpr *getMemberForAccessor(const CXXMemberCallExpr &C) {
+  // Use getCalleeDecl instead of getMethodDecl in order to handle pointer-to-member calls.
   const auto *MethodDecl = dyn_cast_or_null<CXXMethodDecl>(C.getCalleeDecl());
   if (!MethodDecl)
     return nullptr;
diff --git a/clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp b/clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp
index 55fb6549621737a..abebd362bec471f 100644
--- a/clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp
+++ b/clang/unittests/Analysis/FlowSensitive/DataflowEnvironmentTest.cpp
@@ -27,6 +27,7 @@ using namespace dataflow;
 using ::clang::dataflow::test::getFieldValue;
 using ::testing::IsNull;
 using ::testing::NotNull;
+using ::testing::Contains;
 
 class EnvironmentTest : public ::testing::Test {
 protected: