Add qpdf version macros to qpdf/DLL.h

ChangeLog

@@ -1,5 +1,14 @@
 2022-02-04  Jay Berkenbilt  <ejb@ql.org>
 
+	* New preprocessor symbols QPDF_MAJOR_VERSION, QPDF_MINOR_VERSION,
+	QPDF_PATCH_VERSION as numbers and QPDF_VERSION as a string. These
+	can be used for feature testing in code. These are in qpdf/DLL.h,
+	which is included by every header that adds to the public API.
+	Since these constants are introduced in version 10.6, it's
+	important for them to be in a header that everyone already
+	includes so you don't have to try to include a header that won't
+	be there.
+
 	* PointerHolder: deprecate getPointer() and getRefcount(). If you
 	don't want to disable deprecation warnings in general but are not
 	ready to tackle this change yet, you can define

TODO

@@ -3,9 +3,6 @@
 
 * Close issue #556.
 
-* Add QPDF_MAJOR_VERSION, QPDF_MINOR_VERSION to some header, possibly
-  dll.h since this is everywhere that there's API
-
 * Add user-defined initializer `QPDFObjectHandle operator ""_qpdf` to
   be like QPDFObjectHandle::parse: `auto oh = "<< /a (b) >>"_qpdf;`
 

include/qpdf/DLL.h

@@ -23,6 +23,12 @@
 #ifndef QPDF_DLL_HH
 #define QPDF_DLL_HH
 
+/* The first version of qpdf to include the version constants is 10.6.0. */
+#define QPDF_MAJOR_VERSION 10
+#define QPDF_MINOR_VERSION 5
+#define QPDF_PATCH_VERSION 0
+#define QPDF_VERSION "10.5.0"
+
 #if (defined _WIN32 || defined __CYGWIN__) && defined(DLL_EXPORT)
 # define QPDF_DLL __declspec(dllexport)
 # define QPDF_DLL_CLASS

include/qpdf/QPDF.hh

@@ -52,7 +52,8 @@ class BitWriter;
 class QPDF
 {
   public:
-    // Get the current version of the QPDF software
+    // Get the current version of the QPDF software. See also
+    // qpdf/Version.h
     QPDF_DLL
     static std::string const& QPDFVersion();
 

include/qpdf/Version.h

@@ -0,0 +1,34 @@
+/* Copyright (c) 2005-2021 Jay Berkenbilt
+ *
+ * This file is part of qpdf.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *   http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ * Versions of qpdf prior to version 7 were released under the terms
+ * of version 2.0 of the Artistic License. At your option, you may
+ * continue to consider qpdf to be licensed under those terms. Please
+ * see the manual for additional information.
+ */
+
+#ifndef QPDF_VERSION_H
+#define QPDF_VERSION_H
+
+/* The first version of qpdf to have these constants was 10.6.0. This
+ * file is included by qpdf/DLL.h, which is included by everything
+ * that adds to the public API, so you can test for these values
+ * without explicitly including this file in code that has to work
+ * with older qpdf than 10.6.0.
+ */
+
+
+#endif /* QPDF_VERSION_H */

libqpdf/QPDF.cc

@@ -25,7 +25,7 @@
 #include <qpdf/QPDF_Stream.hh>
 #include <qpdf/QPDF_Array.hh>
 
-std::string QPDF::qpdf_version = "10.5.0";
+std::string QPDF::qpdf_version(QPDF_VERSION);
 
 static char const* EMPTY_PDF =
     "%PDF-1.3\n"

make_dist

@@ -121,16 +121,37 @@ sub get_version_from_configure
 
 sub get_version_from_source
 {
-    my $fh = safe_open("libqpdf/QPDF.cc");
+    my $fh = safe_open("include/qpdf/DLL.h");
     my $code_version = 'unknown';
+    my $major = '';
+    my $minor = '';
+    my $patch = '';
     while (<$fh>)
     {
-        if (m/QPDF::qpdf_version = \"([^\"]+)\"/)
+        if (m/QPDF_MAJOR_VERSION (\d+)/)
+        {
+            $major = $1;
+        }
+        elsif (m/QPDF_MINOR_VERSION (\d+)/)
+        {
+            $minor = $1;
+        }
+        elsif (m/QPDF_PATCH_VERSION (\d+)/)
+        {
+            $patch = $1;
+        }
+        elsif (m/QPDF_VERSION \"([^\"]+)\"/)
         {
             $code_version = $1;
-            last;
         }
     }
+    my $t = sprintf("%s.%s.%s", $major, $minor, $patch);
+    if ($t ne $code_version)
+    {
+        die "$whoami: version is inconsistent in DLL.h:" .
+            " $t vs $code_version\n";
+    }
+
     $fh->close();
     $code_version;
 }