merge main into amd-staging (llvm#936)

Author: ronlieb

clang-tools-extra/docs/ReleaseNotes.rst

@@ -122,7 +122,8 @@ Changes in existing checks
 - Improved :doc:`misc-const-correctness
   <clang-tidy/checks/misc/const-correctness>` check by adding the option
   `AllowedTypes`, that excludes specified types from const-correctness
-  checking.
+  checking and fixing false positives when modifying variant by ``operator[]``
+  with template in parameters.
 
 - Improved :doc:`misc-redundant-expression
   <clang-tidy/checks/misc/redundant-expression>` check by providing additional

clang-tools-extra/test/clang-tidy/checkers/misc/const-correctness-values.cpp

@@ -998,3 +998,11 @@ void member_pointer_const(Value &x, PointerToConstMemberFunction m) {
   // CHECK-MESSAGES:[[@LINE-1]]:3: warning: variable 'member_pointer_tmp' of type 'Value &' can be declared 'const'
   (member_pointer_tmp.*m)();
 }
+
+namespace gh127776_false_positive {
+template <class T> struct vector { T &operator[](int t); };
+template <typename T> void f() {
+  vector<int> x;
+  x[T{}] = 3;
+}
+} // namespace gh127776_false_positive

clang/docs/ReleaseNotes.rst

@@ -114,6 +114,8 @@ Non-comprehensive list of changes in this release
 New Compiler Flags
 ------------------
 
+- New option ``-Wundef-true`` added and enabled by default to warn when `true` is used in the C preprocessor without being defined before C23.
+
 - New option ``-fprofile-continuous`` added to enable continuous profile syncing to file (#GH124353, `docs <https://clang.llvm.org/docs/UsersManual.html#cmdoption-fprofile-continuous>`_).
   The feature has `existed <https://clang.llvm.org/docs/SourceBasedCodeCoverage.html#running-the-instrumented-program>`_)
   for a while and this is just a user facing option.

clang/include/clang/Basic/DiagnosticGroups.td

@@ -791,6 +791,8 @@ def ReservedIdAsMacroAlias : DiagGroup<"reserved-id-macro", [ReservedIdAsMacro]>
 def ReservedAttributeIdentifier : DiagGroup<"reserved-attribute-identifier">;
 def RestrictExpansionMacro : DiagGroup<"restrict-expansion">;
 def FinalMacro : DiagGroup<"final-macro">;
+def UndefinedTrueIdentifier : DiagGroup<"undef-true">;
+def UndefinedIdentifier : DiagGroup<"undef", [UndefinedTrueIdentifier]>;
 
 // Just silence warnings about -Wstrict-aliasing for now.
 def : DiagGroup<"strict-aliasing=0">;

clang/include/clang/Basic/DiagnosticLexKinds.td

@@ -392,7 +392,10 @@ def pp_macro_not_used : Warning<"macro is not used">, DefaultIgnore,
   InGroup<DiagGroup<"unused-macros">>;
 def warn_pp_undef_identifier : Warning<
   "%0 is not defined, evaluates to 0">,
-  InGroup<DiagGroup<"undef">>, DefaultIgnore;
+  InGroup<UndefinedIdentifier>, DefaultIgnore;
+def warn_pp_undef_true_identifier : Warning<
+  "'true' is not defined, evaluates to 0">,
+  InGroup<UndefinedTrueIdentifier>;
 def warn_pp_undef_prefix : Warning<
   "%0 is not defined, evaluates to 0">,
   InGroup<DiagGroup<"undef-prefix">>, DefaultIgnore;

clang/lib/Analysis/ExprMutationAnalyzer.cpp

@@ -80,6 +80,17 @@ static bool canExprResolveTo(const Expr *Source, const Expr *Target) {
 
 namespace {
 
+// `ArraySubscriptExpr` can switch base and idx, e.g. `a[4]` is the same as
+// `4[a]`. When type is dependent, we conservatively assume both sides are base.
+AST_MATCHER_P(ArraySubscriptExpr, hasBaseConservative,
+              ast_matchers::internal::Matcher<Expr>, InnerMatcher) {
+  if (Node.isTypeDependent()) {
+    return InnerMatcher.matches(*Node.getLHS(), Finder, Builder) ||
+           InnerMatcher.matches(*Node.getRHS(), Finder, Builder);
+  }
+  return InnerMatcher.matches(*Node.getBase(), Finder, Builder);
+}
+
 AST_MATCHER(Type, isDependentType) { return Node.isDependentType(); }
 
 AST_MATCHER_P(LambdaExpr, hasCaptureInit, const Expr *, E) {
@@ -513,8 +524,8 @@ ExprMutationAnalyzer::Analyzer::findArrayElementMutation(const Expr *Exp) {
   // Check whether any element of an array is mutated.
   const auto SubscriptExprs = match(
       findAll(arraySubscriptExpr(
-                  anyOf(hasBase(canResolveToExpr(Exp)),
-                        hasBase(implicitCastExpr(allOf(
+                  anyOf(hasBaseConservative(canResolveToExpr(Exp)),
+                        hasBaseConservative(implicitCastExpr(allOf(
                             hasCastKind(CK_ArrayToPointerDecay),
                             hasSourceExpression(canResolveToExpr(Exp)))))))
                   .bind(NodeID<Expr>::value)),
@@ -716,7 +727,8 @@ ExprMutationAnalyzer::Analyzer::findPointeeValueMutation(const Expr *Exp) {
                    unaryOperator(hasOperatorName("*"),
                                  hasUnaryOperand(canResolveToExprPointee(Exp))),
                    // deref by []
-                   arraySubscriptExpr(hasBase(canResolveToExprPointee(Exp)))))
+                   arraySubscriptExpr(
+                       hasBaseConservative(canResolveToExprPointee(Exp)))))
               .bind(NodeID<Expr>::value))),
       Stm, Context);
   return findExprMutation(Matches);

clang/lib/Lex/PPExpressions.cpp

@@ -257,12 +257,14 @@ static bool EvaluateValue(PPValue &Result, Token &PeekTok, DefinedTracker &DT,
         // preprocessor keywords and it wasn't macro expanded, it turns
         // into a simple 0
         if (ValueLive) {
-          PP.Diag(PeekTok, diag::warn_pp_undef_identifier) << II;
+          unsigned DiagID = II->getName() == "true"
+                                ? diag::warn_pp_undef_true_identifier
+                                : diag::warn_pp_undef_identifier;
+          PP.Diag(PeekTok, DiagID) << II;
 
           const DiagnosticsEngine &DiagEngine = PP.getDiagnostics();
           // If 'Wundef' is enabled, do not emit 'undef-prefix' diagnostics.
-          if (DiagEngine.isIgnored(diag::warn_pp_undef_identifier,
-                                   PeekTok.getLocation())) {
+          if (DiagEngine.isIgnored(DiagID, PeekTok.getLocation())) {
             const std::vector<std::string> UndefPrefixes =
                 DiagEngine.getDiagnosticOptions().UndefPrefixes;
             const StringRef IdentifierName = II->getName();

clang/test/Preprocessor/warn-macro-undef-true.c

@@ -0,0 +1,78 @@
+// RUN: %clang_cc1 %s -Eonly -std=c89 -verify=undef-true
+// RUN: %clang_cc1 %s -Eonly -std=c99 -verify=undef-true
+// RUN: %clang_cc1 %s -Eonly -std=c11 -verify=undef-true
+// RUN: %clang_cc1 %s -Eonly -std=c17 -verify=undef-true
+// RUN: %clang_cc1 %s -Eonly -std=c23 -verify=undef-true
+
+#if __STDC_VERSION__ >= 202311L
+/* undef-true-no-diagnostics */
+#endif
+
+#define FOO true
+#if FOO /* #1 */
+#endif
+#if __STDC_VERSION__ < 202311L
+/* undef-true-warning@#1 {{'true' is not defined, evaluates to 0}} */
+#endif
+
+#if true /* #2 */
+#endif
+#if __STDC_VERSION__ < 202311L
+/* undef-true-warning@#2 {{'true' is not defined, evaluates to 0}} */
+#endif
+
+#if false || true /* #3 */
+#endif
+#if __STDC_VERSION__ < 202311L
+/* undef-true-warning@#3 {{'true' is not defined, evaluates to 0}} */
+#endif
+
+#define true 1
+
+#define FOO true
+#if FOO
+#endif
+
+#if true
+#endif
+
+#if false || true
+#endif
+
+#undef true
+
+#define FOO true
+#if FOO /* #4 */
+#endif
+#if __STDC_VERSION__ < 202311L
+/* undef-true-warning@#4 {{'true' is not defined, evaluates to 0}} */
+#endif
+
+#if true /* #5 */
+#endif
+#if __STDC_VERSION__ < 202311L
+/* undef-true-warning@#5 {{'true' is not defined, evaluates to 0}} */
+#endif
+
+#if false || true /* #6 */
+#endif
+#if __STDC_VERSION__ < 202311L
+/* undef-true-warning@#6 {{'true' is not defined, evaluates to 0}} */
+#endif
+
+#define true true
+#if true /* #7 */
+#endif
+#if __STDC_VERSION__ < 202311L
+/* undef-true-warning@#7 {{'true' is not defined, evaluates to 0}} */
+#endif
+#undef true
+
+/* Test that #pragma-enabled 'Wundef' can override 'Wundef-true' */
+#pragma clang diagnostic warning "-Wundef"
+#if true /* #8 */
+#endif
+#pragma clang diagnostic ignored "-Wundef"
+#if __STDC_VERSION__ < 202311L
+/* undef-true-warning@#8 {{'true' is not defined, evaluates to 0}} */
+#endif

clang/unittests/Analysis/ExprMutationAnalyzerTest.cpp

@@ -870,6 +870,19 @@ TEST(ExprMutationAnalyzerTest, TemplateWithArrayToPointerDecay) {
   EXPECT_THAT(mutatedBy(ResultsY, AST.get()), ElementsAre("y"));
 }
 
+TEST(ExprMutationAnalyzerTest, T1) {
+  const auto AST = buildASTFromCodeWithArgs(
+      "template <class T> struct vector { T &operator[](int t); };"
+      "template <typename T> void func() {"
+      "  vector<int> x;"
+      "  x[T{}] = 3;"
+      "}",
+      {"-fno-delayed-template-parsing"});
+  const auto Results =
+      match(withEnclosingCompound(declRefTo("x")), AST->getASTContext());
+  EXPECT_TRUE(isMutated(Results, AST.get()));
+}
+
 // section: special case: all created references are non-mutating themself
 //          and therefore all become 'const'/the value is not modified!
 

libcxx/docs/Status/Cxx2cIssues.csv

@@ -37,7 +37,7 @@
 "`LWG3973 <https://wg21.link/LWG3973>`__","Monadic operations should be ADL-proof","2023-11 (Kona)","","",""
 "`LWG3974 <https://wg21.link/LWG3974>`__","``mdspan::operator[]`` should not copy ``OtherIndexTypes``","2023-11 (Kona)","","",""
 "`LWG3987 <https://wg21.link/LWG3987>`__","Including ``<flat_foo>`` doesn't provide ``std::begin``/``end``","2023-11 (Kona)","","",""
-"`LWG3990 <https://wg21.link/LWG3990>`__","Program-defined specializations of ``std::tuple`` and ``std::variant`` can't be properly supported","2023-11 (Kona)","","",""
+"`LWG3990 <https://wg21.link/LWG3990>`__","Program-defined specializations of ``std::tuple`` and ``std::variant`` can't be properly supported","2023-11 (Kona)","|Complete|","21",""
 "`LWG4001 <https://wg21.link/LWG4001>`__","``iota_view`` should provide ``empty``","2023-11 (Kona)","|Complete|","19",""
 "","","","","",""
 "`LWG3767 <https://wg21.link/LWG3767>`__","``codecvt<charN_t, char8_t, mbstate_t>`` incorrectly added to locale","2024-03 (Tokyo)","","",""