[𝘀𝗽𝗿] changes introduced through rebase

Created using spr 1.3.5-bogner

[skip ci]

clang-tools-extra/include-cleaner/lib/WalkAST.cpp

@@ -271,15 +271,13 @@ class ASTWalker : public RecursiveASTVisitor<ASTWalker> {
   // specialized template. Implicit ones are filtered out by RAV.
   bool
   VisitClassTemplateSpecializationDecl(ClassTemplateSpecializationDecl *CTSD) {
-    // if (CTSD->isExplicitSpecialization())
     if (clang::isTemplateExplicitInstantiationOrSpecialization(
             CTSD->getTemplateSpecializationKind()))
       report(CTSD->getLocation(),
              CTSD->getSpecializedTemplate()->getTemplatedDecl());
     return true;
   }
   bool VisitVarTemplateSpecializationDecl(VarTemplateSpecializationDecl *VTSD) {
-    // if (VTSD->isExplicitSpecialization())
     if (clang::isTemplateExplicitInstantiationOrSpecialization(
             VTSD->getTemplateSpecializationKind()))
       report(VTSD->getLocation(),

clang/docs/ReleaseNotes.rst

@@ -65,9 +65,20 @@ C++ Specific Potentially Breaking Changes
   `-Wno-enum-constexpr-conversion`, to allow for a transition period for users.
   Now, in Clang 20, **it is no longer possible to suppress the diagnostic**.
 
+- Extraneous template headers are now ill-formed by default.
+  This error can be disable with ``-Wno-error=extraneous-template-head``.
+
+  .. code-block:: c++
+
+    template <> // error: extraneous template head
+    template <typename T>
+    void f();
+
 ABI Changes in This Version
 ---------------------------
 
+- Fixed Microsoft name mangling of placeholder, auto and decltype(auto), return types for MSVC 1920+. This change resolves incompatibilities with code compiled by MSVC 1920+ but will introduce incompatibilities with code compiled by earlier versions of Clang unless such code is built with the compiler option -fms-compatibility-version=19.14 to imitate the MSVC 1914 mangling behavior.
+
 AST Dumping Potentially Breaking Changes
 ----------------------------------------
 
@@ -383,6 +394,36 @@ Moved checkers
 Sanitizers
 ----------
 
+- Added the ``-fsanitize-overflow-pattern-exclusion=`` flag which can be used
+  to disable specific overflow-dependent code patterns. The supported patterns
+  are: ``add-overflow-test``, ``negated-unsigned-const``, and
+  ``post-decr-while``. The sanitizer instrumentation can be toggled off for all
+  available patterns by specifying ``all``. Conversely, you can disable all
+  exclusions with ``none``.
+
+  .. code-block:: c++
+
+     /// specified with ``-fsanitize-overflow-pattern-exclusion=add-overflow-test``
+     int common_overflow_check_pattern(unsigned base, unsigned offset) {
+       if (base + offset < base) { /* ... */ } // The pattern of `a + b < a`, and other re-orderings, won't be instrumented
+     }
+
+     /// specified with ``-fsanitize-overflow-pattern-exclusion=negated-unsigned-const``
+     void negation_overflow() {
+       unsigned long foo = -1UL; // No longer causes a negation overflow warning
+       unsigned long bar = -2UL; // and so on...
+     }
+
+     /// specified with ``-fsanitize-overflow-pattern-exclusion=post-decr-while``
+     void while_post_decrement() {
+       unsigned char count = 16;
+       while (count--) { /* ... */} // No longer causes unsigned-integer-overflow sanitizer to trip
+     }
+
+  Many existing projects have a large amount of these code patterns present.
+  This new flag should allow those projects to enable integer sanitizers with
+  less noise.
+
 Python Binding Changes
 ----------------------
 - Fixed an issue that led to crashes when calling ``Type.get_exception_specification_kind``.

clang/docs/UndefinedBehaviorSanitizer.rst

@@ -293,6 +293,48 @@ To silence reports from unsigned integer overflow, you can set
 ``-fsanitize-recover=unsigned-integer-overflow``, is particularly useful for
 providing fuzzing signal without blowing up logs.
 
+Disabling instrumentation for common overflow patterns
+------------------------------------------------------
+
+There are certain overflow-dependent or overflow-prone code patterns which
+produce a lot of noise for integer overflow/truncation sanitizers. Negated
+unsigned constants, post-decrements in a while loop condition and simple
+overflow checks are accepted and pervasive code patterns. However, the signal
+received from sanitizers instrumenting these code patterns may be too noisy for
+some projects. To disable instrumentation for these common patterns one should
+use ``-fsanitize-overflow-pattern-exclusion=``.
+
+Currently, this option supports three overflow-dependent code idioms:
+
+``negated-unsigned-const``
+
+.. code-block:: c++
+
+    /// -fsanitize-overflow-pattern-exclusion=negated-unsigned-const
+    unsigned long foo = -1UL; // No longer causes a negation overflow warning
+    unsigned long bar = -2UL; // and so on...
+
+``post-decr-while``
+
+.. code-block:: c++
+
+    /// -fsanitize-overflow-pattern-exclusion=post-decr-while
+    unsigned char count = 16;
+    while (count--) { /* ... */ } // No longer causes unsigned-integer-overflow sanitizer to trip
+
+``add-overflow-test``
+
+.. code-block:: c++
+
+    /// -fsanitize-overflow-pattern-exclusion=add-overflow-test
+    if (base + offset < base) { /* ... */ } // The pattern of `a + b < a`, and other re-orderings,
+                                            // won't be instrumented (same for signed types)
+
+You can enable all exclusions with
+``-fsanitize-overflow-pattern-exclusion=all`` or disable all exclusions with
+``-fsanitize-overflow-pattern-exclusion=none``. Specifying ``none`` has
+precedence over other values.
+
 Issue Suppression
 =================
 

clang/include/clang/AST/Decl.h

@@ -3206,6 +3206,10 @@ class FieldDecl : public DeclaratorDecl, public Mergeable<FieldDecl> {
   /// Set the C++11 in-class initializer for this member.
   void setInClassInitializer(Expr *NewInit);
 
+  /// Find the FieldDecl specified in a FAM's "counted_by" attribute. Returns
+  /// \p nullptr if either the attribute or the field doesn't exist.
+  const FieldDecl *findCountedByField() const;
+
 private:
   void setLazyInClassInitializer(LazyDeclStmtPtr NewInit);
 

clang/include/clang/AST/Expr.h

@@ -4043,6 +4043,15 @@ class BinaryOperator : public Expr {
   void setHasStoredFPFeatures(bool B) { BinaryOperatorBits.HasFPFeatures = B; }
   bool hasStoredFPFeatures() const { return BinaryOperatorBits.HasFPFeatures; }
 
+  /// Set and get the bit that informs arithmetic overflow sanitizers whether
+  /// or not they should exclude certain BinaryOperators from instrumentation
+  void setExcludedOverflowPattern(bool B) {
+    BinaryOperatorBits.ExcludedOverflowPattern = B;
+  }
+  bool hasExcludedOverflowPattern() const {
+    return BinaryOperatorBits.ExcludedOverflowPattern;
+  }
+
   /// Get FPFeatures from trailing storage
   FPOptionsOverride getStoredFPFeatures() const {
     assert(hasStoredFPFeatures());

clang/include/clang/AST/Stmt.h

@@ -650,6 +650,11 @@ class alignas(void *) Stmt {
     LLVM_PREFERRED_TYPE(bool)
     unsigned HasFPFeatures : 1;
 
+    /// Whether or not this BinaryOperator should be excluded from integer
+    /// overflow sanitization.
+    LLVM_PREFERRED_TYPE(bool)
+    unsigned ExcludedOverflowPattern : 1;
+
     SourceLocation OpLoc;
   };
 

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -5428,7 +5428,8 @@ def err_template_spec_extra_headers : Error<
   "extraneous template parameter list in template specialization or "
   "out-of-line template definition">;
 def ext_template_spec_extra_headers : ExtWarn<
-  "extraneous template parameter list in template specialization">;
+  "extraneous template parameter list in template specialization">,
+   InGroup<DiagGroup<"extraneous-template-head">>, DefaultError;
 def note_explicit_template_spec_does_not_need_header : Note<
   "'template<>' header not required for explicitly-specialized class %0 "
   "declared here">;

clang/include/clang/Basic/LangOptions.def

@@ -406,6 +406,8 @@ VALUE_LANGOPT(TrivialAutoVarInitMaxSize, 32, 0,
              "stop trivial automatic variable initialization if var size exceeds the specified size (in bytes). Must be greater than 0.")
 ENUM_LANGOPT(SignedOverflowBehavior, SignedOverflowBehaviorTy, 2, SOB_Undefined,
              "signed integer overflow handling")
+LANGOPT(IgnoreNegationOverflow, 1, 0, "ignore overflow caused by negation")
+LANGOPT(SanitizeOverflowIdioms, 1, 1, "enable instrumentation for common overflow idioms")
 ENUM_LANGOPT(ThreadModel  , ThreadModelKind, 2, ThreadModelKind::POSIX, "Thread Model")
 
 BENIGN_LANGOPT(ArrowDepth, 32, 256,

clang/include/clang/Basic/LangOptions.h

@@ -367,6 +367,21 @@ class LangOptionsBase {
     PerThread,
   };
 
+  /// Exclude certain code patterns from being instrumented by arithmetic
+  /// overflow sanitizers
+  enum OverflowPatternExclusionKind {
+    /// Don't exclude any overflow patterns from sanitizers
+    None = 1 << 0,
+    /// Exclude all overflow patterns (below)
+    All = 1 << 1,
+    /// if (a + b < a)
+    AddOverflowTest = 1 << 2,
+    /// -1UL
+    NegUnsignedConst = 1 << 3,
+    /// while (count--)
+    PostDecrInWhile = 1 << 4,
+  };
+
   enum class DefaultVisiblityExportMapping {
     None,
     /// map only explicit default visibilities to exported
@@ -555,6 +570,11 @@ class LangOptions : public LangOptionsBase {
   /// The default stream kind used for HIP kernel launching.
   GPUDefaultStreamKind GPUDefaultStream;
 
+  /// Which overflow patterns should be excluded from sanitizer instrumentation
+  unsigned OverflowPatternExclusionMask = 0;
+
+  std::vector<std::string> OverflowPatternExclusionValues;
+
   /// The seed used by the randomize structure layout feature.
   std::string RandstructSeed;
 
@@ -630,6 +650,14 @@ class LangOptions : public LangOptionsBase {
     return MSCompatibilityVersion >= MajorVersion * 100000U;
   }
 
+  bool isOverflowPatternExcluded(OverflowPatternExclusionKind Kind) const {
+    if (OverflowPatternExclusionMask & OverflowPatternExclusionKind::None)
+      return false;
+    if (OverflowPatternExclusionMask & OverflowPatternExclusionKind::All)
+      return true;
+    return OverflowPatternExclusionMask & Kind;
+  }
+
   /// Reset all of the options that are not considered when building a
   /// module.
   void resetNonModularOptions();

clang/include/clang/Driver/Options.td

@@ -2565,6 +2565,11 @@ defm sanitize_stats : BoolOption<"f", "sanitize-stats",
           "Disable">,
   BothFlags<[], [ClangOption], " sanitizer statistics gathering.">>,
   Group<f_clang_Group>;
+def fsanitize_overflow_pattern_exclusion_EQ : CommaJoined<["-"], "fsanitize-overflow-pattern-exclusion=">,
+  HelpText<"Specify the overflow patterns to exclude from artihmetic sanitizer instrumentation">,
+  Visibility<[ClangOption, CC1Option]>,
+  Values<"none,all,add-overflow-test,negated-unsigned-const,post-decr-while">,
+  MarshallingInfoStringVector<LangOpts<"OverflowPatternExclusionValues">>;
 def fsanitize_thread_memory_access : Flag<["-"], "fsanitize-thread-memory-access">,
                                      Group<f_clang_Group>,
                                      HelpText<"Enable memory access instrumentation in ThreadSanitizer (default)">;

clang/include/clang/Driver/SanitizerArgs.h

@@ -33,6 +33,7 @@ class SanitizerArgs {
   std::vector<std::string> BinaryMetadataIgnorelistFiles;
   int CoverageFeatures = 0;
   int BinaryMetadataFeatures = 0;
+  int OverflowPatternExclusions = 0;
   int MsanTrackOrigins = 0;
   bool MsanUseAfterDtor = true;
   bool MsanParamRetval = true;

clang/lib/AST/Decl.cpp

@@ -4678,6 +4678,19 @@ void FieldDecl::printName(raw_ostream &OS, const PrintingPolicy &Policy) const {
   DeclaratorDecl::printName(OS, Policy);
 }
 
+const FieldDecl *FieldDecl::findCountedByField() const {
+  const auto *CAT = getType()->getAs<CountAttributedType>();
+  if (!CAT)
+    return nullptr;
+
+  const auto *CountDRE = cast<DeclRefExpr>(CAT->getCountExpr());
+  const auto *CountDecl = CountDRE->getDecl();
+  if (const auto *IFD = dyn_cast<IndirectFieldDecl>(CountDecl))
+    CountDecl = IFD->getAnonField();
+
+  return dyn_cast<FieldDecl>(CountDecl);
+}
+
 //===----------------------------------------------------------------------===//
 // TagDecl Implementation
 //===----------------------------------------------------------------------===//

clang/lib/AST/Expr.cpp

@@ -4759,6 +4759,53 @@ ParenListExpr *ParenListExpr::CreateEmpty(const ASTContext &Ctx,
   return new (Mem) ParenListExpr(EmptyShell(), NumExprs);
 }
 
+/// Certain overflow-dependent code patterns can have their integer overflow
+/// sanitization disabled. Check for the common pattern `if (a + b < a)` and
+/// return the resulting BinaryOperator responsible for the addition so we can
+/// elide overflow checks during codegen.
+static std::optional<BinaryOperator *>
+getOverflowPatternBinOp(const BinaryOperator *E) {
+  Expr *Addition, *ComparedTo;
+  if (E->getOpcode() == BO_LT) {
+    Addition = E->getLHS();
+    ComparedTo = E->getRHS();
+  } else if (E->getOpcode() == BO_GT) {
+    Addition = E->getRHS();
+    ComparedTo = E->getLHS();
+  } else {
+    return {};
+  }
+
+  const Expr *AddLHS = nullptr, *AddRHS = nullptr;
+  BinaryOperator *BO = dyn_cast<BinaryOperator>(Addition);
+
+  if (BO && BO->getOpcode() == clang::BO_Add) {
+    // now store addends for lookup on other side of '>'
+    AddLHS = BO->getLHS();
+    AddRHS = BO->getRHS();
+  }
+
+  if (!AddLHS || !AddRHS)
+    return {};
+
+  const Decl *LHSDecl, *RHSDecl, *OtherDecl;
+
+  LHSDecl = AddLHS->IgnoreParenImpCasts()->getReferencedDeclOfCallee();
+  RHSDecl = AddRHS->IgnoreParenImpCasts()->getReferencedDeclOfCallee();
+  OtherDecl = ComparedTo->IgnoreParenImpCasts()->getReferencedDeclOfCallee();
+
+  if (!OtherDecl)
+    return {};
+
+  if (!LHSDecl && !RHSDecl)
+    return {};
+
+  if ((LHSDecl && LHSDecl == OtherDecl && LHSDecl != RHSDecl) ||
+      (RHSDecl && RHSDecl == OtherDecl && RHSDecl != LHSDecl))
+    return BO;
+  return {};
+}
+
 BinaryOperator::BinaryOperator(const ASTContext &Ctx, Expr *lhs, Expr *rhs,
                                Opcode opc, QualType ResTy, ExprValueKind VK,
                                ExprObjectKind OK, SourceLocation opLoc,
@@ -4768,8 +4815,15 @@ BinaryOperator::BinaryOperator(const ASTContext &Ctx, Expr *lhs, Expr *rhs,
   assert(!isCompoundAssignmentOp() &&
          "Use CompoundAssignOperator for compound assignments");
   BinaryOperatorBits.OpLoc = opLoc;
+  BinaryOperatorBits.ExcludedOverflowPattern = 0;
   SubExprs[LHS] = lhs;
   SubExprs[RHS] = rhs;
+  if (Ctx.getLangOpts().isOverflowPatternExcluded(
+          LangOptions::OverflowPatternExclusionKind::AddOverflowTest)) {
+    std::optional<BinaryOperator *> Result = getOverflowPatternBinOp(this);
+    if (Result.has_value())
+      Result.value()->BinaryOperatorBits.ExcludedOverflowPattern = 1;
+  }
   BinaryOperatorBits.HasFPFeatures = FPFeatures.requiresTrailingStorage();
   if (hasStoredFPFeatures())
     setStoredFPFeatures(FPFeatures);