[clang][analyzer]: fix 'clang-analyzer-optin.cplusplus.UninitializedObject false positive with unnamed fields'

Author: YLChenZ

clang/lib/StaticAnalyzer/Checkers/UninitializedObject/UninitializedObjectChecker.cpp

@@ -17,14 +17,15 @@
 //
 //===----------------------------------------------------------------------===//
 
-#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
 #include "UninitializedObject.h"
 #include "clang/ASTMatchers/ASTMatchFinder.h"
 #include "clang/Driver/DriverDiagnostic.h"
+#include "clang/StaticAnalyzer/Checkers/BuiltinCheckerRegistration.h"
 #include "clang/StaticAnalyzer/Core/BugReporter/BugType.h"
 #include "clang/StaticAnalyzer/Core/Checker.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/CheckerContext.h"
 #include "clang/StaticAnalyzer/Core/PathSensitive/DynamicType.h"
+#include "clang/include/clang/AST/Decl.h"
 
 using namespace clang;
 using namespace clang::ento;
@@ -291,7 +292,10 @@ bool FindUninitializedFields::isNonUnionUninit(const TypedValueRegion *R,
 
   // Are all of this non-union's fields initialized?
   for (const FieldDecl *I : RD->fields()) {
-
+    // Skip checking for unnamed bitfield
+    if (I->isUnnamedBitField()) {
+      continue;
+    }
     const auto FieldVal =
         State->getLValue(I, loc::MemRegionVal(R)).castAs<loc::MemRegionVal>();
     const auto *FR = FieldVal.getRegionAs<FieldRegion>();

clang/test/Analysis/unnamed_bitfield.cpp

@@ -0,0 +1,16 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=optin.cplusplus.UninitializedObject -verify %s
+// expected-no-diagnostics
+
+struct S
+{
+    S(bool b)
+    : b(b)
+    {}
+    bool b{false};
+    long long : 7; // padding
+};
+
+void f()
+{
+    S s(true);
+}