Add test for exception handling

There have been issues reported where exceptions are not thrown
properly across shared library/DLL boundaries, so add a test
specifically to ensure that exceptions are caught as thrown.

qpdf/qtest/qpdf.test

@@ -178,6 +178,16 @@ $td->runtest("check final version",
              {$td->STRING => "test 54 done\n", $td->EXIT_STATUS => 0},
              $td->NORMALIZE_NEWLINES);
 
+show_ntests();
+# ----------
+$td->notify("--- Exceptions ---");
+$n_tests += 1;
+
+$td->runtest("check exception handling",
+             {$td->COMMAND => "test_driver 61 -"},
+             {$td->FILE => "exceptions.out", $td->EXIT_STATUS => 0},
+             $td->NORMALIZE_NEWLINES);
+
 show_ntests();
 # ----------
 $td->notify("--- Dangling Refs ---");

qpdf/qtest/qpdf/exceptions.out

@@ -0,0 +1,5 @@
+Caught QPDFExc as expected
+Caught QPDFSystemError as expected
+Caught logic_error as expected
+Caught runtime_error as expected
+test 61 done

qpdf/test_driver.cc

@@ -16,6 +16,7 @@
 #include <qpdf/Pl_Buffer.hh>
 #include <qpdf/Pl_Flate.hh>
 #include <qpdf/QPDFWriter.hh>
+#include <qpdf/QPDFSystemError.hh>
 #include <iostream>
 #include <sstream>
 #include <algorithm>
@@ -269,6 +270,10 @@ void runtest(int n, char const* filename1, char const* arg2)
 	pdf.processMemoryFile((std::string(filename1) + ".pdf").c_str(),
                               p, size);
     }
+    else if (n == 61)
+    {
+        // Ignore filename argument entirely
+    }
     else if (n % 2 == 0)
     {
         if (n % 4 == 0)
@@ -2046,6 +2051,45 @@ void runtest(int n, char const* filename1, char const* arg2)
         w.setStaticID(true);
         w.write();
     }
+    else if (n == 61)
+    {
+        // Test to make sure exceptions can be caught properly across
+        // shared library boundaries.
+	pdf.setAttemptRecovery(false);
+        pdf.setSuppressWarnings(true);
+        try
+        {
+            pdf.processMemoryFile("empty", "", 0);
+        }
+        catch (QPDFExc& e)
+        {
+            std::cout << "Caught QPDFExc as expected" << std::endl;
+        }
+        try
+        {
+            QUtil::safe_fopen("/does/not/exist", "r");
+        }
+        catch (QPDFSystemError& e)
+        {
+            std::cout << "Caught QPDFSystemError as expected" << std::endl;
+        }
+        try
+        {
+            QUtil::int_to_string_base(0, 12);
+        }
+        catch (std::logic_error& e)
+        {
+            std::cout << "Caught logic_error as expected" << std::endl;
+        }
+        try
+        {
+            QUtil::toUTF8(0xffffffff);
+        }
+        catch (std::runtime_error& e)
+        {
+            std::cout << "Caught runtime_error as expected" << std::endl;
+        }
+    }
     else
     {
 	throw std::runtime_error(std::string("invalid test ") +