[analyzer] Remove redundant bug type DoubleDelete (#147542)

This commit removes the DoubleDelete bug type from `MallocChecker.cpp`
because it's completely redundant with the `DoubleFree` bug (which is
already used for all allocator families, including new/delete).

This simplifies the code of the checker and prevents the potential
confusion caused by two semantically equivalent and very similar, but
not identical bug report messages.

Author: NagyDonat

clang/lib/StaticAnalyzer/Checkers/MallocChecker.cpp

@@ -346,10 +346,6 @@ namespace {
   };
 
 BUGTYPE_PROVIDER(DoubleFree, "Double free")
-// TODO: Remove DoubleDelete as a separate bug type and when it would be
-// emitted, emit DoubleFree reports instead. (Note that DoubleFree is already
-// used for all allocation families, not just malloc/free.)
-BUGTYPE_PROVIDER(DoubleDelete, "Double delete")
 
 struct Leak : virtual public CheckerFrontend {
   // Leaks should not be reported if they are post-dominated by a sink:
@@ -410,8 +406,7 @@ class MallocChecker
   DynMemFrontend<DoubleFree, Leak, UseFree, BadFree, FreeAlloca, OffsetFree,
                  UseZeroAllocated>
       MallocChecker;
-  DynMemFrontend<DoubleFree, DoubleDelete, UseFree, BadFree, OffsetFree,
-                 UseZeroAllocated>
+  DynMemFrontend<DoubleFree, UseFree, BadFree, OffsetFree, UseZeroAllocated>
       NewDeleteChecker;
   DynMemFrontend<Leak> NewDeleteLeaksChecker;
   DynMemFrontend<FreeAlloca, MismatchedDealloc> MismatchedDeallocatorChecker;
@@ -784,9 +779,6 @@ class MallocChecker
   void checkUseZeroAllocated(SymbolRef Sym, CheckerContext &C,
                              const Stmt *S) const;
 
-  /// If in \p S \p Sym is being freed, check whether \p Sym was already freed.
-  bool checkDoubleDelete(SymbolRef Sym, CheckerContext &C) const;
-
   /// Check if the function is known to free memory, or if it is
   /// "interesting" and should be modeled explicitly.
   ///
@@ -848,8 +840,6 @@ class MallocChecker
   void HandleDoubleFree(CheckerContext &C, SourceRange Range, bool Released,
                         SymbolRef Sym, SymbolRef PrevSym) const;
 
-  void HandleDoubleDelete(CheckerContext &C, SymbolRef Sym) const;
-
   void HandleUseZeroAlloc(CheckerContext &C, SourceRange Range,
                           SymbolRef Sym) const;
 
@@ -2737,7 +2727,8 @@ void MallocChecker::HandleDoubleFree(CheckerContext &C, SourceRange Range,
         (Released ? "Attempt to free released memory"
                   : "Attempt to free non-owned memory"),
         N);
-    R->addRange(Range);
+    if (Range.isValid())
+      R->addRange(Range);
     R->markInteresting(Sym);
     if (PrevSym)
       R->markInteresting(PrevSym);
@@ -2746,26 +2737,6 @@ void MallocChecker::HandleDoubleFree(CheckerContext &C, SourceRange Range,
   }
 }
 
-void MallocChecker::HandleDoubleDelete(CheckerContext &C, SymbolRef Sym) const {
-  const DoubleDelete *Frontend = getRelevantFrontendAs<DoubleDelete>(C, Sym);
-  if (!Frontend)
-    return;
-  if (!Frontend->isEnabled()) {
-    C.addSink();
-    return;
-  }
-
-  if (ExplodedNode *N = C.generateErrorNode()) {
-
-    auto R = std::make_unique<PathSensitiveBugReport>(
-        Frontend->DoubleDeleteBug, "Attempt to delete released memory", N);
-
-    R->markInteresting(Sym);
-    R->addVisitor<MallocBugVisitor>(Sym);
-    C.emitReport(std::move(R));
-  }
-}
-
 void MallocChecker::HandleUseZeroAlloc(CheckerContext &C, SourceRange Range,
                                        SymbolRef Sym) const {
   const UseZeroAllocated *Frontend =
@@ -3136,10 +3107,22 @@ void MallocChecker::checkPreCall(const CallEvent &Call,
     return;
   }
 
+  // If we see a `CXXDestructorCall` (that is, an _implicit_ destructor call)
+  // to a region that's symbolic and known to be already freed, then it must be
+  // implicitly triggered by a `delete` expression. In this situation we should
+  // emit a `DoubleFree` report _now_ (before entering the call to the
+  // destructor) because otherwise the destructor call can trigger a
+  // use-after-free bug (by accessing any member variable) and that would be
+  // (technically valid, but) less user-friendly report than the `DoubleFree`.
   if (const auto *DC = dyn_cast<CXXDestructorCall>(&Call)) {
     SymbolRef Sym = DC->getCXXThisVal().getAsSymbol();
-    if (!Sym || checkDoubleDelete(Sym, C))
+    if (!Sym)
       return;
+    if (isReleased(Sym, C)) {
+      HandleDoubleFree(C, SourceRange(), /*Released=*/true, Sym,
+                       /*PrevSym=*/nullptr);
+      return;
+    }
   }
 
   // We need to handle getline pre-conditions here before the pointed region
@@ -3321,15 +3304,6 @@ void MallocChecker::checkUseZeroAllocated(SymbolRef Sym, CheckerContext &C,
   }
 }
 
-bool MallocChecker::checkDoubleDelete(SymbolRef Sym, CheckerContext &C) const {
-
-  if (isReleased(Sym, C)) {
-    HandleDoubleDelete(C, Sym);
-    return true;
-  }
-  return false;
-}
-
 // Check if the location is a freed symbolic region.
 void MallocChecker::checkLocation(SVal l, bool isLoad, const Stmt *S,
                                   CheckerContext &C) const {

clang/test/Analysis/NewDelete-checker-test.cpp

@@ -412,7 +412,7 @@ class DerefClass{
 void testDoubleDeleteClassInstance() {
   DerefClass *foo = new DerefClass();
   delete foo;
-  delete foo; // newdelete-warning {{Attempt to delete released memory}}
+  delete foo; // newdelete-warning {{Attempt to free released memory}}
 }
 
 class EmptyClass{
@@ -424,7 +424,7 @@ class EmptyClass{
 void testDoubleDeleteEmptyClass() {
   EmptyClass *foo = new EmptyClass();
   delete foo;
-  delete foo; // newdelete-warning {{Attempt to delete released memory}}
+  delete foo; // newdelete-warning {{Attempt to free released memory}}
 }
 
 struct Base {