Bug 1152921 - Don't send an uninitialized PrintData over IPC when cancelling print dialog (or failing ShowPrintDialog for other reasons). r=mconley

This fixes a crash in debug builds (due to uninitialized booleans) when
canceling a print dialog.

embedding/components/printingui/ipc/PPrintSettingsDialog.ipdl

@@ -9,12 +9,19 @@ include protocol PPrinting;
 namespace mozilla {
 namespace embedding {
 
+// A PrintData for success, a failure nsresult for failure.
+union PrintDataOrNSResult
+{
+  PrintData;
+  nsresult;
+};
+
 protocol PPrintSettingsDialog
 {
   manager PPrinting;
 
 child:
-  __delete__(nsresult rv, PrintData data);
+  __delete__(PrintDataOrNSResult result);
 };
 
 } // namespace embedding

embedding/components/printingui/ipc/PrintSettingsDialogChild.cpp

@@ -21,11 +21,15 @@ PrintSettingsDialogChild::~PrintSettingsDialogChild()
 }
 
 bool
-PrintSettingsDialogChild::Recv__delete__(const nsresult& aResult,
-                                         const PrintData& aData)
+PrintSettingsDialogChild::Recv__delete__(const PrintDataOrNSResult& aData)
 {
-  mResult = aResult;
-  mData = aData;
+  if (aData.type() == PrintDataOrNSResult::Tnsresult) {
+    mResult = aData.get_nsresult();
+    MOZ_ASSERT(NS_FAILED(mResult), "expected a failure result");
+  } else {
+    mResult = NS_OK;
+    mData = aData.get_PrintData();
+  }
   mReturned = true;
   return true;
 }

embedding/components/printingui/ipc/PrintSettingsDialogChild.h

@@ -16,8 +16,7 @@ class PrintSettingsDialogChild final : public PPrintSettingsDialogChild
 public:
   MOZ_IMPLICIT PrintSettingsDialogChild();
 
-  virtual bool Recv__delete__(const nsresult& aResult,
-                              const PrintData& aData) override;
+  virtual bool Recv__delete__(const PrintDataOrNSResult& aData) override;
 
   bool returned() { return mReturned; };
   nsresult result() { return mResult; };

embedding/components/printingui/ipc/PrintingParent.cpp

@@ -117,7 +117,11 @@ PrintingParent::RecvShowPrintDialog(PPrintSettingsDialogParent* aDialog,
   // to hear about the print settings. We return the results
   // with an async message which frees the child process from
   // its nested event loop.
-  mozilla::unused << aDialog->Send__delete__(aDialog, rv, resultData);
+  if (NS_FAILED(rv)) {
+    mozilla::unused << aDialog->Send__delete__(aDialog, rv);
+  } else {
+    mozilla::unused << aDialog->Send__delete__(aDialog, resultData);
+  }
   return true;
 }