Revert r309106 "Recommit r308327 2nd time: Add a warning for missing"

The warning fires on non-suspicious code in Chromium. Reverting until a
solution is figured out.

> Recommit r308327 2nd time: Add a warning for missing
> '#pragma pack (pop)' and suspicious uses of '#pragma pack' in included files
>
> The first recommit (r308441) caused a "non-default #pragma pack value might
> change the alignment of struct or union members in the included file" warning
> in LLVM itself. This recommit tweaks the added warning to avoid warnings for
> #includes that don't have any records that are affected by the non-default
> alignment. This tweak avoids the previously emitted warning in LLVM.
>
> Original message:
>
> This commit adds a new -Wpragma-pack warning. It warns in the following cases:
>
> - When a translation unit is missing terminating #pragma pack (pop) directives.
> - When entering an included file if the current alignment value as determined
>   by '#pragma pack' directives is different from the default alignment value.
> - When leaving an included file that changed the state of the current alignment
>   value.
>
> rdar://10184173
>
> Differential Revision: https://reviews.llvm.org/D35484

llvm-svn: 309186

5 files changed, 5 insertions, 120 deletions

diff --git a/clang/lib/Parse/ParsePragma.cpp b/clang/lib/Parse/ParsePragma.cpp
index c5215ffceeb..262743756a6 100644
--- a/clang/lib/Parse/ParsePragma.cpp
+++ b/clang/lib/Parse/ParsePragma.cpp
@@ -422,20 +422,15 @@ void Parser::HandlePragmaPack() {
   assert(Tok.is(tok::annot_pragma_pack));
   PragmaPackInfo *Info =
     static_cast<PragmaPackInfo *>(Tok.getAnnotationValue());
-  SourceLocation PragmaLoc = Tok.getLocation();
+  SourceLocation PragmaLoc = ConsumeAnnotationToken();
   ExprResult Alignment;
   if (Info->Alignment.is(tok::numeric_constant)) {
     Alignment = Actions.ActOnNumericConstant(Info->Alignment);
-    if (Alignment.isInvalid()) {
-      ConsumeAnnotationToken();
+    if (Alignment.isInvalid())
       return;
-    }
   }
   Actions.ActOnPragmaPack(PragmaLoc, Info->Action, Info->SlotLabel,
                           Alignment.get());
-  // Consume the token after processing the pragma to enable pragma-specific
-  // #include warnings.
-  ConsumeAnnotationToken();
 }
 
 void Parser::HandlePragmaMSStruct() {
diff --git a/clang/lib/Sema/Sema.cpp b/clang/lib/Sema/Sema.cpp
index 40ffa09de1a..6f0db6ce1c6 100644
--- a/clang/lib/Sema/Sema.cpp
+++ b/clang/lib/Sema/Sema.cpp
@@ -70,49 +70,6 @@ void Sema::ActOnTranslationUnitScope(Scope *S) {
   PushDeclContext(S, Context.getTranslationUnitDecl());
 }
 
-namespace clang {
-namespace sema {
-
-class SemaPPCallbacks : public PPCallbacks {
-  Sema *S = nullptr;
-  llvm::SmallVector<SourceLocation, 8> IncludeStack;
-
-public:
-  void set(Sema &S) { this->S = &S; }
-
-  void reset() { S = nullptr; }
-
-  virtual void FileChanged(SourceLocation Loc, FileChangeReason Reason,
-                           SrcMgr::CharacteristicKind FileType,
-                           FileID PrevFID) override {
-    if (!S)
-      return;
-    switch (Reason) {
-    case EnterFile: {
-      SourceManager &SM = S->getSourceManager();
-      SourceLocation IncludeLoc = SM.getIncludeLoc(SM.getFileID(Loc));
-      if (IncludeLoc.isValid()) {
-        IncludeStack.push_back(IncludeLoc);
-        S->DiagnoseNonDefaultPragmaPack(
-            Sema::PragmaPackDiagnoseKind::NonDefaultStateAtInclude, IncludeLoc);
-      }
-      break;
-    }
-    case ExitFile:
-      if (!IncludeStack.empty())
-        S->DiagnoseNonDefaultPragmaPack(
-            Sema::PragmaPackDiagnoseKind::ChangedStateAtExit,
-            IncludeStack.pop_back_val());
-      break;
-    default:
-      break;
-    }
-  }
-};
-
-} // end namespace sema
-} // end namespace clang
-
 Sema::Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
            TranslationUnitKind TUKind, CodeCompleteConsumer *CodeCompleter)
     : ExternalSource(nullptr), isMultiplexExternalSource(false),
@@ -165,12 +122,6 @@ Sema::Sema(Preprocessor &pp, ASTContext &ctxt, ASTConsumer &consumer,
 
   // Initilization of data sharing attributes stack for OpenMP
   InitDataSharingAttributesStack();
-
-  std::unique_ptr<sema::SemaPPCallbacks> Callbacks =
-      llvm::make_unique<sema::SemaPPCallbacks>();
-  SemaPPCallbackHandler = Callbacks.get();
-  PP.addPPCallbacks(std::move(Callbacks));
-  SemaPPCallbackHandler->set(*this);
 }
 
 void Sema::addImplicitTypedef(StringRef Name, QualType T) {
@@ -355,10 +306,6 @@ Sema::~Sema() {
   // Destroys data sharing attributes stack for OpenMP
   DestroyDataSharingAttributesStack();
 
-  // Detach from the PP callback handler which outlives Sema since it's owned
-  // by the preprocessor.
-  SemaPPCallbackHandler->reset();
-
   assert(DelayedTypos.empty() && "Uncorrected typos!");
 }
 
@@ -819,7 +766,6 @@ void Sema::ActOnEndOfTranslationUnit() {
     CheckDelayedMemberExceptionSpecs();
   }
 
-  DiagnoseUnterminatedPragmaPack();
   DiagnoseUnterminatedPragmaAttribute();
 
   // All delayed member exception specs should be checked or we end up accepting
diff --git a/clang/lib/Sema/SemaAttr.cpp b/clang/lib/Sema/SemaAttr.cpp
index f7f1f618739..8c13ead6445 100644
--- a/clang/lib/Sema/SemaAttr.cpp
+++ b/clang/lib/Sema/SemaAttr.cpp
@@ -61,17 +61,6 @@ void Sema::AddAlignmentAttributesForRecord(RecordDecl *RD) {
       RD->addAttr(MaxFieldAlignmentAttr::CreateImplicit(Context,
                                                         Alignment * 8));
   }
-  if (PackIncludeStack.empty())
-    return;
-  // The #pragma pack affected a record in an included file,  so Clang should
-  // warn when that pragma was written in a file that included the included
-  // file.
-  for (auto &PackedInclude : llvm::reverse(PackIncludeStack)) {
-    if (PackedInclude.CurrentPragmaLocation != PackStack.CurrentPragmaLocation)
-      break;
-    if (PackedInclude.HasNonDefaultValue)
-      PackedInclude.ShouldWarnOnInclude = true;
-  }
 }
 
 void Sema::AddMsStructLayoutForRecord(RecordDecl *RD) {
@@ -213,47 +202,6 @@ void Sema::ActOnPragmaPack(SourceLocation PragmaLoc, PragmaMsStackAction Action,
   PackStack.Act(PragmaLoc, Action, SlotLabel, AlignmentVal);
 }
 
-void Sema::DiagnoseNonDefaultPragmaPack(PragmaPackDiagnoseKind Kind,
-                                        SourceLocation IncludeLoc) {
-  if (Kind == PragmaPackDiagnoseKind::NonDefaultStateAtInclude) {
-    SourceLocation PrevLocation = PackStack.CurrentPragmaLocation;
-    // Warn about non-default alignment at #includes (without redundant
-    // warnings for the same directive in nested includes).
-    // The warning is delayed until the end of the file to avoid warnings
-    // for files that don't have any records that are affected by the modified
-    // alignment.
-    bool HasNonDefaultValue =
-        PackStack.hasValue() &&
-        (PackIncludeStack.empty() ||
-         PackIncludeStack.back().CurrentPragmaLocation != PrevLocation);
-    PackIncludeStack.push_back(
-        {PackStack.CurrentValue,
-         PackStack.hasValue() ? PrevLocation : SourceLocation(),
-         HasNonDefaultValue, /*ShouldWarnOnInclude*/ false});
-    return;
-  }
-
-  assert(Kind == PragmaPackDiagnoseKind::ChangedStateAtExit && "invalid kind");
-  PackIncludeState PrevPackState = PackIncludeStack.pop_back_val();
-  if (PrevPackState.ShouldWarnOnInclude) {
-    // Emit the delayed non-default alignment at #include warning.
-    Diag(IncludeLoc, diag::warn_pragma_pack_non_default_at_include);
-    Diag(PrevPackState.CurrentPragmaLocation, diag::note_pragma_pack_here);
-  }
-  // Warn about modified alignment after #includes.
-  if (PrevPackState.CurrentValue != PackStack.CurrentValue) {
-    Diag(IncludeLoc, diag::warn_pragma_pack_modified_after_include);
-    Diag(PackStack.CurrentPragmaLocation, diag::note_pragma_pack_here);
-  }
-}
-
-void Sema::DiagnoseUnterminatedPragmaPack() {
-  if (PackStack.Stack.empty())
-    return;
-  for (const auto &StackSlot : llvm::reverse(PackStack.Stack))
-    Diag(StackSlot.PragmaPushLocation, diag::warn_pragma_pack_no_pop_eof);
-}
-
 void Sema::ActOnPragmaMSStruct(PragmaMSStructKind Kind) { 
   MSStructPragmaOn = (Kind == PMSST_ON);
 }
@@ -301,8 +249,7 @@ void Sema::PragmaStack<ValueType>::Act(SourceLocation PragmaLocation,
     return;
   }
   if (Action & PSK_Push)
-    Stack.emplace_back(StackSlotLabel, CurrentValue, CurrentPragmaLocation,
-                       PragmaLocation);
+    Stack.push_back(Slot(StackSlotLabel, CurrentValue, CurrentPragmaLocation));
   else if (Action & PSK_Pop) {
     if (!StackSlotLabel.empty()) {
       // If we've got a label, try to find it and jump there.
diff --git a/clang/lib/Serialization/ASTReader.cpp b/clang/lib/Serialization/ASTReader.cpp
index eb49a90d721..cae99e8bf0a 100644
--- a/clang/lib/Serialization/ASTReader.cpp
+++ b/clang/lib/Serialization/ASTReader.cpp
@@ -3382,7 +3382,6 @@ ASTReader::ReadASTBlock(ModuleFile &F, unsigned ClientLoadCapabilities) {
         PragmaPackStackEntry Entry;
         Entry.Value = Record[Idx++];
         Entry.Location = ReadSourceLocation(F, Record[Idx++]);
-        Entry.PushLocation = ReadSourceLocation(F, Record[Idx++]);
         PragmaPackStrings.push_back(ReadString(Record, Idx));
         Entry.SlotLabel = PragmaPackStrings.back();
         PragmaPackStack.push_back(Entry);
@@ -7571,14 +7570,13 @@ void ASTReader::UpdateSema() {
              "Expected a default alignment value");
       SemaObj->PackStack.Stack.emplace_back(
           PragmaPackStack.front().SlotLabel, SemaObj->PackStack.CurrentValue,
-          SemaObj->PackStack.CurrentPragmaLocation,
-          PragmaPackStack.front().PushLocation);
+          SemaObj->PackStack.CurrentPragmaLocation);
       DropFirst = true;
     }
     for (const auto &Entry :
          llvm::makeArrayRef(PragmaPackStack).drop_front(DropFirst ? 1 : 0))
       SemaObj->PackStack.Stack.emplace_back(Entry.SlotLabel, Entry.Value,
-                                            Entry.Location, Entry.PushLocation);
+                                            Entry.Location);
     if (PragmaPackCurrentLocation.isInvalid()) {
       assert(*PragmaPackCurrentValue == SemaObj->PackStack.DefaultValue &&
              "Expected a default alignment value");
diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 9a739579b31..a875e627bdf 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -4295,7 +4295,6 @@ void ASTWriter::WritePackPragmaOptions(Sema &SemaRef) {
   for (const auto &StackEntry : SemaRef.PackStack.Stack) {
     Record.push_back(StackEntry.Value);
     AddSourceLocation(StackEntry.PragmaLocation, Record);
-    AddSourceLocation(StackEntry.PragmaPushLocation, Record);
     AddString(StackEntry.StackSlotLabel, Record);
   }
   Stream.EmitRecord(PACK_PRAGMA_OPTIONS, Record);