-Wpragma-pack: add an additional note and fixit when warning

about unterminated push directives that are followed by a reset
('#pragma pack()')

This has been suggested by Hans Wennborg.

llvm-svn: 309559

1 files changed, 15 insertions, 1 deletions

diff --git a/clang/lib/Sema/SemaAttr.cpp b/clang/lib/Sema/SemaAttr.cpp
index f7f1f618739..4ba2a317e1f 100644
--- a/clang/lib/Sema/SemaAttr.cpp
+++ b/clang/lib/Sema/SemaAttr.cpp
@@ -250,8 +250,22 @@ void Sema::DiagnoseNonDefaultPragmaPack(PragmaPackDiagnoseKind Kind,
 void Sema::DiagnoseUnterminatedPragmaPack() {
   if (PackStack.Stack.empty())
     return;
-  for (const auto &StackSlot : llvm::reverse(PackStack.Stack))
+  bool IsInnermost = true;
+  for (const auto &StackSlot : llvm::reverse(PackStack.Stack)) {
     Diag(StackSlot.PragmaPushLocation, diag::warn_pragma_pack_no_pop_eof);
+    // The user might have already reset the alignment, so suggest replacing
+    // the reset with a pop.
+    if (IsInnermost && PackStack.CurrentValue == PackStack.DefaultValue) {
+      DiagnosticBuilder DB = Diag(PackStack.CurrentPragmaLocation,
+                                  diag::note_pragma_pack_pop_instead_reset);
+      SourceLocation FixItLoc = Lexer::findLocationAfterToken(
+          PackStack.CurrentPragmaLocation, tok::l_paren, SourceMgr, LangOpts,
+          /*SkipTrailing=*/false);
+      if (FixItLoc.isValid())
+        DB << FixItHint::CreateInsertion(FixItLoc, "pop");
+    }
+    IsInnermost = false;
+  }
 }
 
 void Sema::ActOnPragmaMSStruct(PragmaMSStructKind Kind) {