Add a warning for missing '#pragma pack (pop)' and suspicious uses

of '#pragma pack' in included files

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: 308327

1 files changed, 36 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaAttr.cpp b/clang/lib/Sema/SemaAttr.cpp
index 8c13ead6445..7193450220a 100644
--- a/clang/lib/Sema/SemaAttr.cpp
+++ b/clang/lib/Sema/SemaAttr.cpp
@@ -202,6 +202,40 @@ 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).
+    if (PackStack.hasValue() &&
+        (PackIncludeStack.empty() ||
+         PackIncludeStack.back().second != PrevLocation)) {
+      Diag(IncludeLoc, diag::warn_pragma_pack_non_default_at_include);
+      Diag(PrevLocation, diag::note_pragma_pack_here);
+    }
+    PackIncludeStack.push_back(
+        {PackStack.CurrentValue,
+         PackStack.hasValue() ? PrevLocation : SourceLocation()});
+    return;
+  }
+
+  assert(Kind == PragmaPackDiagnoseKind::ChangedStateAtExit && "invalid kind");
+  unsigned PreviousValue = PackIncludeStack.pop_back_val().first;
+  // Warn about modified alignment after #includes.
+  if (PreviousValue != 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);
 }
@@ -249,7 +283,8 @@ void Sema::PragmaStack<ValueType>::Act(SourceLocation PragmaLocation,
     return;
   }
   if (Action & PSK_Push)
-    Stack.push_back(Slot(StackSlotLabel, CurrentValue, CurrentPragmaLocation));
+    Stack.emplace_back(StackSlotLabel, CurrentValue, CurrentPragmaLocation,
+                       PragmaLocation);
   else if (Action & PSK_Pop) {
     if (!StackSlotLabel.empty()) {
       // If we've got a label, try to find it and jump there.