From 039eb4a253c7faed9a906a7f45f2c9f1f2a76002 Mon Sep 17 00:00:00 2001
From: Jay Berkenbilt <ejb@ql.org>
Date: Tue, 23 Feb 2021 08:08:48 -0500
Subject: [PATCH] Fix input file = output file test for split pages

---
 ChangeLog            |  6 ++++++
 qpdf/qpdf.cc         |  9 ++++++++-
 qpdf/qtest/qpdf.test | 12 +++++++++++-
 3 files changed, 25 insertions(+), 2 deletions(-)

diff --git a/ChangeLog b/ChangeLog
index ab4bb571..3a53753d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2021-02-23  Jay Berkenbilt  <ejb@ql.org>
+
+	* The test for the input and output files being the same wasn't
+	implemented correctly for --split-pages since the specified output
+	file is really a pattern, not the actual output file.
+
 2021-02-22  Jay Berkenbilt  <ejb@ql.org>
 
 	* From qpdf CLI, --pages and --split-pages will properly preserve
diff --git a/qpdf/qpdf.cc b/qpdf/qpdf.cc
index 75f046ca..ea52d6d3 100644
--- a/qpdf/qpdf.cc
+++ b/qpdf/qpdf.cc
@@ -3738,7 +3738,7 @@ ArgParser::doFinalChecks()
         }
     }
 
-    if (QUtil::same_file(o.infilename, o.outfilename))
+    if ((! o.split_pages) && QUtil::same_file(o.infilename, o.outfilename))
     {
         QTC::TC("qpdf", "qpdf same file error");
         usage("input file and output file are the same;"
@@ -6389,6 +6389,13 @@ static void do_split_pages(QPDF& pdf, Options& o, bool& warnings)
                 QUtil::uint_to_string(last, QIntC::to_int(pageno_len));
         }
         std::string outfile = before + page_range + after;
+        if (QUtil::same_file(o.infilename, outfile.c_str()))
+        {
+            std::cerr << whoami
+                      << ": split pages would overwrite input file with "
+                      << outfile << std::endl;
+            exit(EXIT_ERROR);
+        }
         QPDFWriter w(outpdf, outfile.c_str());
         set_writer_options(outpdf, o, w);
         w.write();
diff --git a/qpdf/qtest/qpdf.test b/qpdf/qtest/qpdf.test
index da98020a..7bfe21cd 100644
--- a/qpdf/qtest/qpdf.test
+++ b/qpdf/qtest/qpdf.test
@@ -1825,14 +1825,24 @@ $td->runtest("out of range in deleted object",
 show_ntests();
 # ----------
 $td->notify("--- Overwrite self ---");
-$n_tests += 1;
+$n_tests += 3;
 
 copy("minimal.pdf", "a.pdf");
+copy("minimal.pdf", "split-out.pdf");
 # Also tests @- for reading args from stdin
 $td->runtest("don't overwrite self",
              {$td->COMMAND => "(echo a.pdf; echo a.pdf) | qpdf \@-"},
              {$td->REGEXP => "input file and output file are the same.*",
               $td->EXIT_STATUS => 2});
+$td->runtest("output is not really output for split",
+             {$td->COMMAND => "qpdf --split-pages split-out.pdf split-out.pdf"},
+             {$td->STRING => "", $td->EXIT_STATUS => 0});
+$td->runtest("don't overwrite self (split)",
+             {$td->COMMAND =>
+                  "qpdf --split-pages split-out-1.pdf split-out.pdf"},
+             {$td->REGEXP =>
+                  ".*split pages would overwrite.* split-out-1.pdf",
+                  $td->EXIT_STATUS => 2});
 
 show_ntests();
 # ----------