Adapted MemRegion::getDescriptiveName to handle ElementRegions (#85104)

Fixes #84463

Changes:
- Adapted MemRegion::getDescriptiveName
- Added unittest to check name for a given clang::ento::ElementRegion
- Some format changes due to clang-format

---------

Co-authored-by: Andreas Steinhausen <andreas.steinhausen@concenrio.io>
Co-authored-by: Balazs Benics <benicsbalazs@gmail.com>

clang/lib/StaticAnalyzer/Core/MemRegion.cpp

@@ -720,13 +720,21 @@ std::string MemRegion::getDescriptiveName(bool UseQuotes) const {
       CI->getValue().toString(Idx);
       ArrayIndices = (llvm::Twine("[") + Idx.str() + "]" + ArrayIndices).str();
     }
-    // If not a ConcreteInt, try to obtain the variable
-    // name by calling 'getDescriptiveName' recursively.
+    // Index is symbolic, but may have a descriptive name.
     else {
-      std::string Idx = ER->getDescriptiveName(false);
-      if (!Idx.empty()) {
-        ArrayIndices = (llvm::Twine("[") + Idx + "]" + ArrayIndices).str();
-      }
+      auto SI = ER->getIndex().getAs<nonloc::SymbolVal>();
+      if (!SI)
+        return "";
+
+      const MemRegion *OR = SI->getAsSymbol()->getOriginRegion();
+      if (!OR)
+        return "";
+
+      std::string Idx = OR->getDescriptiveName(false);
+      if (Idx.empty())
+        return "";
+
+      ArrayIndices = (llvm::Twine("[") + Idx + "]" + ArrayIndices).str();
     }
     R = ER->getSuperRegion();
   }

clang/unittests/StaticAnalyzer/CMakeLists.txt

@@ -11,6 +11,7 @@ add_clang_unittest(StaticAnalysisTests
   CallEventTest.cpp
   ConflictingEvalCallsTest.cpp
   FalsePositiveRefutationBRVisitorTest.cpp
+  MemRegionDescriptiveNameTest.cpp
   NoStateChangeFuncVisitorTest.cpp
   ParamRegionTest.cpp
   RangeSetTest.cpp

clang/unittests/StaticAnalyzer/MemRegionDescriptiveNameTest.cpp

@@ -0,0 +1,145 @@
+//===- MemRegionDescriptiveNameTest.cpp -----------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#include "CheckerRegistration.h"
+#include "clang/StaticAnalyzer/Core/Checker.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/MemRegion.h"
+#include "gtest/gtest.h"
+#include <fstream>
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+
+class DescriptiveNameChecker : public Checker<check::PreCall> {
+public:
+  void checkPreCall(const CallEvent &Call, CheckerContext &C) const {
+    if (!HandlerFn.matches(Call))
+      return;
+
+    const MemRegion *ArgReg = Call.getArgSVal(0).getAsRegion();
+    assert(ArgReg && "expecting a location as the first argument");
+
+    auto DescriptiveName = ArgReg->getDescriptiveName(/*UseQuotes=*/false);
+    if (ExplodedNode *Node = C.generateNonFatalErrorNode(C.getState())) {
+      auto Report =
+          std::make_unique<PathSensitiveBugReport>(Bug, DescriptiveName, Node);
+      C.emitReport(std::move(Report));
+    }
+  }
+
+private:
+  const BugType Bug{this, "DescriptiveNameBug"};
+  const CallDescription HandlerFn = {{"reportDescriptiveName"}, 1};
+};
+
+void addDescriptiveNameChecker(AnalysisASTConsumer &AnalysisConsumer,
+                               AnalyzerOptions &AnOpts) {
+  AnOpts.CheckersAndPackages = {{"DescriptiveNameChecker", true}};
+  AnalysisConsumer.AddCheckerRegistrationFn([](CheckerRegistry &Registry) {
+    Registry.addChecker<DescriptiveNameChecker>("DescriptiveNameChecker",
+                                                "Desc", "DocsURI");
+  });
+}
+
+bool runChecker(StringRef Code, std::string &Output) {
+  return runCheckerOnCode<addDescriptiveNameChecker>(Code.str(), Output,
+                                                     /*OnlyEmitWarnings=*/true);
+}
+
+TEST(MemRegionDescriptiveNameTest, ConcreteIntElementRegionIndex) {
+  StringRef Code = R"cpp(
+void reportDescriptiveName(int *p);
+const unsigned int index = 1;
+extern int array[3];
+void top() {
+  reportDescriptiveName(&array[index]);
+})cpp";
+
+  std::string Output;
+  ASSERT_TRUE(runChecker(Code, Output));
+  EXPECT_EQ(Output, "DescriptiveNameChecker: array[1]\n");
+}
+
+TEST(MemRegionDescriptiveNameTest, SymbolicElementRegionIndex) {
+  StringRef Code = R"cpp(
+void reportDescriptiveName(int *p);
+extern unsigned int index;
+extern int array[3];
+void top() {
+  reportDescriptiveName(&array[index]);
+})cpp";
+
+  std::string Output;
+  ASSERT_TRUE(runChecker(Code, Output));
+  EXPECT_EQ(Output, "DescriptiveNameChecker: array[index]\n");
+}
+
+TEST(MemRegionDescriptiveNameTest, SymbolicElementRegionIndexSymbolValFails) {
+  StringRef Code = R"cpp(
+void reportDescriptiveName(int *p);
+extern int* ptr;
+extern int array[3];
+void top() {
+  reportDescriptiveName(&array[(long)ptr]);
+})cpp";
+
+  std::string Output;
+  ASSERT_TRUE(runChecker(Code, Output));
+  EXPECT_EQ(Output, "DescriptiveNameChecker: \n");
+}
+
+TEST(MemRegionDescriptiveNameTest, SymbolicElementRegionIndexOrigRegionFails) {
+  StringRef Code = R"cpp(
+void reportDescriptiveName(int *p);
+extern int getInt(void);
+extern int array[3];
+void top() {
+  reportDescriptiveName(&array[getInt()]);
+})cpp";
+
+  std::string Output;
+  ASSERT_TRUE(runChecker(Code, Output));
+  EXPECT_EQ(Output, "DescriptiveNameChecker: \n");
+}
+
+TEST(MemRegionDescriptiveNameTest, SymbolicElementRegionIndexDescrNameFails) {
+  StringRef Code = R"cpp(
+void reportDescriptiveName(int *p);
+extern int *ptr;
+extern int array[3];
+void top() {
+  reportDescriptiveName(&array[*ptr]);
+})cpp";
+
+  std::string Output;
+  ASSERT_TRUE(runChecker(Code, Output));
+  EXPECT_EQ(Output, "DescriptiveNameChecker: \n");
+}
+
+TEST(MemRegionDescriptiveNameTest,
+     SymbolicElementRegionIndexIncorrectSymbolName) {
+  StringRef Code = R"cpp(
+void reportDescriptiveName(int *p);
+extern int x, y;
+extern int array[3];
+void top() {
+  y = x;
+  reportDescriptiveName(&array[y]);
+})cpp";
+
+  std::string Output;
+  ASSERT_TRUE(runChecker(Code, Output));
+  // FIXME: Should return array[y], but returns array[x] (OriginRegion).
+  EXPECT_EQ(Output, "DescriptiveNameChecker: array[x]\n");
+}
+
+} // namespace

llvm/utils/gn/secondary/clang/unittests/StaticAnalyzer/BUILD.gn

@@ -19,6 +19,7 @@ unittest("StaticAnalysisTests") {
     "CallEventTest.cpp",
     "ConflictingEvalCallsTest.cpp",
     "FalsePositiveRefutationBRVisitorTest.cpp",
+    "MemRegionDescriptiveNameTest.cpp",
     "NoStateChangeFuncVisitorTest.cpp",
     "ParamRegionTest.cpp",
     "RangeSetTest.cpp",