Improve testing and error handling around operating before processing

1 files changed, 4 insertions, 2 deletions

diff --git a/libqpdf/QPDF.cc b/libqpdf/QPDF.cc
index 4c9296ea..c81aede0 100644
--- a/libqpdf/QPDF.cc
+++ b/libqpdf/QPDF.cc
@@ -85,8 +85,10 @@ class InvalidInputSource: public InputSource
   private:
     void throwException()
     {
-        throw std::runtime_error(
-            "QPDF operation attempted after closing input source");
+        throw std::logic_error(
+            "QPDF operation attempted on a QPDF object with no input source."
+            " QPDF operations are invalid before processFile (or another"
+            " process method) or after closeInputSource");
     }
 };