[Analyzer][WebKit] cherry-pick 2 more checkers

clang/docs/analyzer/checkers.rst

@@ -1423,6 +1423,25 @@ Raw pointers and references to uncounted types can't be used as class members. O
    // ...
  };
 
+.. _webkit-UncountedLambdaCapturesChecker:
+
+webkit.UncountedLambdaCapturesChecker
+"""""""""""""""""""""""""""""""""""""
+Raw pointers and references to uncounted types can't be captured in lambdas. Only ref-counted types are allowed.
+
+.. code-block:: cpp
+
+ struct RefCntbl {
+   void ref() {}
+   void deref() {}
+ };
+
+ void foo(RefCntbl* a, RefCntbl& b) {
+   [&, a](){ // warn about 'a'
+     do_something(b); // warn about 'b'
+   };
+ };
+
 .. _alpha-checkers:
 
 Experimental Checkers
@@ -2482,6 +2501,53 @@ We also define a set of safe transformations which if passed a safe value as an
 - casts
 - unary operators like ``&`` or ``*``
 
+alpha.webkit.UncountedLocalVarsChecker
+""""""""""""""""""""""""""""""""""""""
+The goal of this rule is to make sure that any uncounted local variable is backed by a ref-counted object with lifetime that is strictly larger than the scope of the uncounted local variable. To be on the safe side we require the scope of an uncounted variable to be embedded in the scope of ref-counted object that backs it.
+
+These are examples of cases that we consider safe:
+
+  .. code-block:: cpp
+    void foo1() {
+      RefPtr<RefCountable> counted;
+      // The scope of uncounted is EMBEDDED in the scope of counted.
+      {
+        RefCountable* uncounted = counted.get(); // ok
+      }
+    }
+
+    void foo2(RefPtr<RefCountable> counted_param) {
+      RefCountable* uncounted = counted_param.get(); // ok
+    }
+
+    void FooClass::foo_method() {
+      RefCountable* uncounted = this; // ok
+    }
+
+Here are some examples of situations that we warn about as they *might* be potentially unsafe. The logic is that either we're able to guarantee that an argument is safe or it's considered if not a bug then bug-prone.
+
+  .. code-block:: cpp
+
+    void foo1() {
+      RefCountable* uncounted = new RefCountable; // warn
+    }
+
+    RefCountable* global_uncounted;
+    void foo2() {
+      RefCountable* uncounted = global_uncounted; // warn
+    }
+
+    void foo3() {
+      RefPtr<RefCountable> counted;
+      // The scope of uncounted is not EMBEDDED in the scope of counted.
+      RefCountable* uncounted = counted.get(); // warn
+    }
+
+We don't warn about these cases - we don't consider them necessarily safe but since they are very common and usually safe we'd introduce a lot of false positives otherwise:
+- variable defined in condition part of an ```if``` statement
+- variable defined in init statement condition of a ```for``` statement
+
+For the time being we also don't warn about uninitialized uncounted local variables.
 
 Debug Checkers
 ---------------

clang/include/clang/StaticAnalyzer/Checkers/Checkers.td

@@ -1654,6 +1654,10 @@ def NoUncountedMemberChecker : Checker<"NoUncountedMemberChecker">,
   HelpText<"Check for no uncounted member variables.">,
   Documentation<HasDocumentation>;
 
+def UncountedLambdaCapturesChecker : Checker<"UncountedLambdaCapturesChecker">,
+  HelpText<"Check uncounted lambda captures.">,
+  Documentation<HasDocumentation>;
+
 } // end webkit
 
 let ParentPackage = WebKitAlpha in {
@@ -1662,4 +1666,8 @@ def UncountedCallArgsChecker : Checker<"UncountedCallArgsChecker">,
   HelpText<"Check uncounted call arguments.">,
   Documentation<HasDocumentation>;
 
+def UncountedLocalVarsChecker : Checker<"UncountedLocalVarsChecker">,
+  HelpText<"Check uncounted local variables.">,
+  Documentation<HasDocumentation>;
+
 } // end alpha.webkit

clang/lib/StaticAnalyzer/Checkers/CMakeLists.txt

@@ -127,6 +127,8 @@ add_clang_library(clangStaticAnalyzerCheckers
   WebKit/PtrTypesSemantics.cpp
   WebKit/RefCntblBaseVirtualDtorChecker.cpp
   WebKit/UncountedCallArgsChecker.cpp
+  WebKit/UncountedLambdaCapturesChecker.cpp
+  WebKit/UncountedLocalVarsChecker.cpp
 
   LINK_LIBS
   clangAST

clang/lib/StaticAnalyzer/Checkers/WebKit/UncountedLambdaCapturesChecker.cpp

@@ -0,0 +1,106 @@
+//=======- UncountedLambdaCapturesChecker.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 "DiagOutputUtils.h"
+#include "PtrTypesSemantics.h"
+#include "clang/AST/CXXInheritance.h"
+#include "clang/AST/RecursiveASTVisitor.h"
+#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
+#include "clang/StaticAnalyzer/Core/BugReporter/BugReporter.h"
+#include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
+#include "clang/StaticAnalyzer/Core/Checker.h"
+
+using namespace clang;
+using namespace ento;
+
+namespace {
+class UncountedLambdaCapturesChecker
+    : public Checker<check::ASTDecl<TranslationUnitDecl>> {
+private:
+  BugType Bug{this, "Lambda capture of uncounted variable",
+              "WebKit coding guidelines"};
+  mutable BugReporter *BR;
+
+public:
+  void checkASTDecl(const TranslationUnitDecl *TUD, AnalysisManager &MGR,
+                    BugReporter &BRArg) const {
+    BR = &BRArg;
+
+    // The calls to checkAST* from AnalysisConsumer don't
+    // visit template instantiations or lambda classes. We
+    // want to visit those, so we make our own RecursiveASTVisitor.
+    struct LocalVisitor : public RecursiveASTVisitor<LocalVisitor> {
+      const UncountedLambdaCapturesChecker *Checker;
+      explicit LocalVisitor(const UncountedLambdaCapturesChecker *Checker)
+          : Checker(Checker) {
+        assert(Checker);
+      }
+
+      bool shouldVisitTemplateInstantiations() const { return true; }
+      bool shouldVisitImplicitCode() const { return false; }
+
+      bool VisitLambdaExpr(LambdaExpr *L) {
+        Checker->visitLambdaExpr(L);
+        return true;
+      }
+    };
+
+    LocalVisitor visitor(this);
+    visitor.TraverseDecl(const_cast<TranslationUnitDecl *>(TUD));
+  }
+
+  void visitLambdaExpr(LambdaExpr *L) const {
+    for (const LambdaCapture &C : L->captures()) {
+      if (C.capturesVariable()) {
+        VarDecl *CapturedVar = C.getCapturedVar();
+        if (auto *CapturedVarType = CapturedVar->getType().getTypePtrOrNull()) {
+          if (isUncountedPtr(CapturedVarType)) {
+            reportBug(C, CapturedVar, CapturedVarType);
+          }
+        }
+      }
+    }
+  }
+
+  void reportBug(const LambdaCapture &Capture, VarDecl *CapturedVar,
+                 const Type *T) const {
+    assert(CapturedVar);
+
+    SmallString<100> Buf;
+    llvm::raw_svector_ostream Os(Buf);
+
+    if (Capture.isExplicit()) {
+      Os << "Captured ";
+    } else {
+      Os << "Implicitly captured ";
+    }
+    if (T->isPointerType()) {
+      Os << "raw-pointer ";
+    } else {
+      assert(T->isReferenceType());
+      Os << "reference ";
+    }
+
+    printQuotedQualifiedName(Os, Capture.getCapturedVar());
+    Os << " to uncounted type is unsafe.";
+
+    PathDiagnosticLocation BSLoc(Capture.getLocation(), BR->getSourceManager());
+    auto Report = std::make_unique<BasicBugReport>(Bug, Os.str(), BSLoc);
+    BR->emitReport(std::move(Report));
+  }
+};
+} // namespace
+
+void ento::registerUncountedLambdaCapturesChecker(CheckerManager &Mgr) {
+  Mgr.registerChecker<UncountedLambdaCapturesChecker>();
+}
+
+bool ento::shouldRegisterUncountedLambdaCapturesChecker(
+    const CheckerManager &mgr) {
+  return true;
+}