[clang] [analyzer] Add std::any checker (PR #76580)

[Gábor Spaits via cfe-commits]

================
@@ -0,0 +1,201 @@
+//===- StdAnyChecker.cpp -------------------------------------*- C++ -*----===//
+//
+// 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 "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
+#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
+#include "clang/StaticAnalyzer/Core/Checker.h"
+#include "clang/StaticAnalyzer/Core/CheckerManager.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CallDescription.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CallEvent.h"
+#include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
+#include "llvm/Support/ErrorHandling.h"
+
+#include "TaggedUnionModeling.h"
+
+using namespace clang;
+using namespace ento;
+using namespace tagged_union_modeling;
+
+REGISTER_MAP_WITH_PROGRAMSTATE(AnyHeldTypeMap, const MemRegion *, QualType)
+
+class StdAnyChecker : public Checker<eval::Call, check::RegionChanges> {
+  CallDescription AnyConstructor{{"std", "any", "any"}};
+  CallDescription AnyAsOp{{"std", "any", "operator="}};
+  CallDescription AnyReset{{"std", "any", "reset"}, 0, 0};
+  CallDescription AnyCast{{"std", "any_cast"}, 1, 1};
+
+  BugType BadAnyType{this, "BadAnyType", "BadAnyType"};
+  BugType NullAnyType{this, "NullAnyType", "NullAnyType"};
+
+public:
+  ProgramStateRef
+  checkRegionChanges(ProgramStateRef State,
+                     const InvalidatedSymbols *Invalidated,
+                     ArrayRef<const MemRegion *> ExplicitRegions,
+                     ArrayRef<const MemRegion *> Regions,
+                     const LocationContext *LCtx, const CallEvent *Call) const {
+    if (!Call)
+      return State;
+
+    return removeInformationStoredForDeadInstances<AnyHeldTypeMap>(*Call, State,
+                                                                   Regions);
+  }
+
+  bool evalCall(const CallEvent &Call, CheckerContext &C) const {
+    // Do not take implementation details into consideration
+    if (Call.isCalledFromSystemHeader())
+      return false;
+
+    if (AnyCast.matches(Call))
+      return handleAnyCastCall(Call, C);
+
+    if (AnyReset.matches(Call)) {
+      const auto *AsMemberCall = dyn_cast<CXXMemberCall>(&Call);
+      if (!AsMemberCall)
+        return false;
+
+      const auto *ThisMemRegion = AsMemberCall->getCXXThisVal().getAsRegion();
+      if (!ThisMemRegion)
+        return false;
+
+      setNullTypeAny(ThisMemRegion, C);
+      return true;
+    }
+
+    bool IsAnyConstructor =
+        isa<CXXConstructorCall>(Call) && AnyConstructor.matches(Call);
+    bool IsAnyAssignmentOperatorCall =
+        isa<CXXMemberOperatorCall>(Call) && AnyAsOp.matches(Call);
+
+    if (IsAnyConstructor || IsAnyAssignmentOperatorCall) {
+      auto State = C.getState();
+      SVal ThisSVal = [&]() {
+        if (IsAnyConstructor) {
+          const auto *AsConstructorCall = dyn_cast<CXXConstructorCall>(&Call);
+          return AsConstructorCall->getCXXThisVal();
+        }
+        if (IsAnyAssignmentOperatorCall) {
+          const auto *AsMemberOpCall = dyn_cast<CXXMemberOperatorCall>(&Call);
+          return AsMemberOpCall->getCXXThisVal();
+        }
+        llvm_unreachable("We must have an assignment operator or constructor");
+      }();
+
+      // default constructor call
+      // in this case the any holds a null type
+      if (Call.getNumArgs() == 0) {
+        const auto *ThisMemRegion = ThisSVal.getAsRegion();
+        setNullTypeAny(ThisMemRegion, C);
+        return true;
+      }
+
+      if (Call.getNumArgs() != 1)
+        return false;
+
+      handleConstructorAndAssignment<AnyHeldTypeMap>(Call, C, ThisSVal);
+      return true;
+    }
+    return false;
+  }
+
+private:
+  // When an std::any is rested or default constructed it has a null type.
+  // We represent it by storing a null QualType.
+  void setNullTypeAny(const MemRegion *Mem, CheckerContext &C) const {
+    auto State = C.getState();
+    State = State->set<AnyHeldTypeMap>(Mem, QualType{});
+    C.addTransition(State);
+  }
----------------
spaits wrote:

Now `setNullTypeAny` return a `ProgramStateRef` in which the type for that instance is null. Later the caller of the function can decide what to do with that.

The reason for storing null types is the possibility of an empty `std::any` instance. This is how the checker represents that. There is no type in the instance.

https://github.com/llvm/llvm-project/pull/76580