[clang-tidy] Fix a false positive on modernize-use-nullptr check.

hokein · hokein · commit b780c59b9336 · 2017-02-28T15:29:52.000Z
Summary: The false positive happens on two neighbour CXXDefaultArgExpr AST nodes. like below: ``` CXXFunctionalCastExpr 0x85c9670 <col:7, col:23> 'struct ZZ' functional cast to struct ZZ <ConstructorConversion> `-CXXConstructExpr 0x85c9518 <col:7, col:23> 'struct ZZ' 'void (uint64, const uint64 *)' |-CallExpr 0x85a0a90 <col:10, col:22> 'uint64':'unsigned long long' | |-ImplicitCastExpr 0x85a0a78 <col:10> 'uint64 (*)(uint64)' <FunctionToPointerDecay> | | `-DeclRefExpr 0x85a09f0 <col:10> 'uint64 (uint64)' lvalue Function 0x85a06a0 'Hash' 'uint64 (uint64)' | `-CXXDefaultArgExpr 0x85a0ac8 <<invalid sloc>> 'uint64':'unsigned long long' `-CXXDefaultArgExpr 0x85c94f8 <<invalid sloc>> 'const uint64 *' ``` For each particular CXXDefaultArgExpr node, we need to reset FirstSubExpr, otherwise FirstSubExpr will refer to an incorrect expr. Reviewers: alexfh Reviewed By: alexfh Subscribers: JDevlieghere, cfe-commits Differential Revision: https://reviews.llvm.org/D30412 llvm-svn: 296479
diff --git a/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp b/clang-tools-extra/clang-tidy/modernize/UseNullptrCheck.cpp
@@ -190,8 +190,10 @@ class CastSequenceVisitor : public RecursiveASTVisitor<CastSequenceVisitor> {
   bool VisitStmt(Stmt *S) {
     auto *C = dyn_cast<CastExpr>(S);
     // Catch the castExpr inside cxxDefaultArgExpr.
-    if (auto *E = dyn_cast<CXXDefaultArgExpr>(S))
+    if (auto *E = dyn_cast<CXXDefaultArgExpr>(S)) {
       C = dyn_cast<CastExpr>(E->getExpr());
+      FirstSubExpr = nullptr;
+    }
     if (!C) {
       FirstSubExpr = nullptr;
       return true;
diff --git a/clang-tools-extra/test/clang-tidy/modernize-use-nullptr.cpp b/clang-tools-extra/test/clang-tidy/modernize-use-nullptr.cpp
@@ -228,3 +228,19 @@ struct D {
 void test_default_argument() {
   D(nullptr);
 }
+
+// Test on two neighbour CXXDefaultArgExprs nodes.
+typedef unsigned long long uint64;
+struct ZZ {
+  explicit ZZ(uint64, const uint64* = NULL) {}
+// CHECK-MESSAGES: :[[@LINE-1]]:39: warning: use nullptr
+// CHECK-FIXES: explicit ZZ(uint64, const uint64* = nullptr) {}
+  operator bool()  { return true; }
+};
+
+uint64 Hash(uint64 seed = 0) { return 0; }
+
+void f() {
+  bool a;
+  a = ZZ(Hash());
+}
