[TextDiagnosticBuffer] Fix diagnostic note emission order.

[jdenny]

Summary

The frontend currently groups diagnostics from the command line
according to diagnostic level, but that places all notes last. Fix
that by emitting such diagnostics in the order they were generated.

[rsmith]

Huh, I'm amazed we've had this bug for so long. Thanks!

[jdenny]

Hi Richard. Thanks for accepting. I don't have commit privileges. Would you please commit for me?

include/clang/Frontend/TextDiagnosticBuffer.h

 
 class TextDiagnosticBuffer : public DiagnosticConsumer {
 public:
   typedef std::vector<std::pair<SourceLocation, std::string> > DiagList;
   typedef DiagList::iterator iterator;
   typedef DiagList::const_iterator const_iterator;
 private:
   DiagList Errors, Warnings, Remarks, Notes;
+  /// All - All diagnostics in the order in which they were generated.  That
+  /// order likely doesn't correspond to user input order, but it at least
+  /// keeps notes in the right places.  Each pair in the vector is a diagnostic
+  /// level and an index into the corresponding DiagList above.
+  std::vector<std::pair<DiagnosticsEngine::Level, size_t>> All;
 public:
   const_iterator err_begin() const  { return Errors.begin(); }
   const_iterator err_end() const    { return Errors.end(); }
 
   const_iterator warn_begin() const { return Warnings.begin(); }
   const_iterator warn_end() const   { return Warnings.end(); }
 
   const_iterator remark_begin() const { return Remarks.begin(); }

lib/Frontend/TextDiagnosticBuffer.cpp

void TextDiagnosticBuffer::HandleDiagnostic(DiagnosticsEngine::Level Level,
   DiagnosticConsumer::HandleDiagnostic(Level, Info);
 
   SmallString<100> Buf;
   Info.FormatDiagnostic(Buf);
   switch (Level) {
   default: llvm_unreachable(
                          "Diagnostic not handled during diagnostic buffering!");
   case DiagnosticsEngine::Note:
+    All.emplace_back(Level, Notes.size());
     Notes.emplace_back(Info.getLocation(), Buf.str());
     break;
   case DiagnosticsEngine::Warning:
+    All.emplace_back(Level, Warnings.size());
     Warnings.emplace_back(Info.getLocation(), Buf.str());
     break;
   case DiagnosticsEngine::Remark:
+    All.emplace_back(Level, Remarks.size());
     Remarks.emplace_back(Info.getLocation(), Buf.str());
     break;
   case DiagnosticsEngine::Error:
   case DiagnosticsEngine::Fatal:
+    All.emplace_back(Level, Errors.size());
     Errors.emplace_back(Info.getLocation(), Buf.str());
     break;
   }
 }
 
 void TextDiagnosticBuffer::FlushDiagnostics(DiagnosticsEngine &Diags) const {
-  // FIXME: Flush the diagnostics in order.
-  for (const_iterator it = err_begin(), ie = err_end(); it != ie; ++it)
-    Diags.Report(Diags.getCustomDiagID(DiagnosticsEngine::Error, "%0"))
-        << it->second;
-  for (const_iterator it = warn_begin(), ie = warn_end(); it != ie; ++it)
-    Diags.Report(Diags.getCustomDiagID(DiagnosticsEngine::Warning, "%0"))
-        << it->second;
-  for (const_iterator it = remark_begin(), ie = remark_end(); it != ie; ++it)
-    Diags.Report(Diags.getCustomDiagID(DiagnosticsEngine::Remark, "%0"))
-        << it->second;
-  for (const_iterator it = note_begin(), ie = note_end(); it != ie; ++it)
-    Diags.Report(Diags.getCustomDiagID(DiagnosticsEngine::Note, "%0"))
-        << it->second;
+  for (auto it = All.begin(), ie = All.end(); it != ie; ++it) {
+    auto Diag = Diags.Report(Diags.getCustomDiagID(it->first, "%0"));
+    switch (it->first) {
+    default: llvm_unreachable(
+                           "Diagnostic not handled during diagnostic flushing!");
+    case DiagnosticsEngine::Note:
+      Diag << Notes[it->second].second;
+      break;
+    case DiagnosticsEngine::Warning:
+      Diag << Warnings[it->second].second;
+      break;
+    case DiagnosticsEngine::Remark:
+      Diag << Remarks[it->second].second;
+      break;
+    case DiagnosticsEngine::Error:
+    case DiagnosticsEngine::Fatal:
+      Diag << Errors[it->second].second;
+      break;
+    }
+  }
 }
 

test/Frontend/diagnostics-order.c

+// Make sure a note stays with its associated command-line argument diagnostic.
+// Previously, these diagnostics were grouped by diagnostic level with all
+// notes last.
+//
+// RUN: not %clang_cc1 -O999 -std=bogus %s 2> %t
+// RUN: FileCheck < %t %s
+//
+// CHECK: warning: optimization level '-O999' is not supported
+// CHECK-NEXT: error: invalid value 'bogus' in '-std=bogus'
+// CHECK-NEXT: note: use {{.*}} for {{.*}} standard