Use the default logger for other writes to stdout/stderr

When there is no context for writing output or error messages, use the
default logger.

TODO

@@ -55,30 +55,10 @@ Output Capture
 
 See https://github.com/qpdf/qpdf/issues/691
 
-QPDFLogger maintains pipelines for info, warn, error, and save.
-
-There is a singleton, default QPDFLogger which all QPDF and QPDFJob
-objects get on construction. In most cases, it is not necessary to
-override this. Allow QPDFJob and QPDF to be passed a new logger
-instance. QPDFJob should pass its QPDFLogger to all QPDF objects it
-creates. The main uses cases for this would be for multithreading or
-for having a library that uses QPDF privately and modifies logger
-settings so that it wouldn't interfere with a downstream library or
-application also using qpdf.
-
 There needs to be a C API to QPDFLogger. Use functions like this:
 
 void set_info((*f)(char* data, unsigned int len, void* udata), void* udata);
 
-We should probably deprecate the output/error setters in QPDF and
-QPDFJob. In the meantime, document that they won't work anymore to set
-different outputs with different QPDF objects. We may need to delete
-rather than deprecate these methods.
-
-Find all places in the library that write to stdout/stderr/cout/cerr.
-Also find places that raise exceptions if unable to warn. These should
-use the global output writer.
-
 
 QPDFPagesTree
 =============

include/qpdf/QPDFLogger.hh

@@ -33,6 +33,19 @@ class QPDFLogger
     QPDF_DLL
     QPDFLogger();
 
+    // Return the default logger. In general, you should use the
+    // default logger. You can also create your own loggers and use
+    // them QPDF and QPDFJob objects, but there are few reasons to do
+    // so. One reason may if you are using multiple QPDF or QPDFJob
+    // objects in different threads and want to capture output and
+    // errors to different streams. (Note that a single QPDF or
+    // QPDFJob can't be safely used from multiple threads, but it is
+    // safe to use separate QPDF and QPDFJob objects on separate
+    // threads.) Another possible reason would be if you are writing
+    // an application that uses the qpdf library directly and qpdf is
+    // also used by a downstream library or if you are using qpdf from
+    // a library and don't want to interfere with potential uses of
+    // qpdf by other libraries or applications.
     QPDF_DLL
     static std::shared_ptr<QPDFLogger> defaultLogger();
 

include/qpdf/QPDFObjectHandle.hh

@@ -1411,14 +1411,14 @@ class QPDFObjectHandle
     // End legacy page helpers
 
     // Issue a warning about this object if possible. If the object
-    // has a description, a warning will be issued. Otherwise, if
-    // throw_if_no_description is true, throw an exception. Otherwise
-    // do nothing. Objects read normally from the file have
+    // has a description, a warning will be issued using the owning
+    // QPDF as context. Otherwise, a message will be written to the
+    // default logger's error stream, which is standard error if not
+    // overridden. Objects read normally from the file have
     // descriptions. See comments on setObjectDescription for
     // additional details.
     QPDF_DLL
-    void warnIfPossible(
-        std::string const& warning, bool throw_if_no_description = false);
+    void warnIfPossible(std::string const& warning);
 
     // Initializers for objects.  This Factory class gives the QPDF
     // class specific permission to call factory methods without

libqpdf/QPDFArgParser.cc

@@ -1,6 +1,7 @@
 #include <qpdf/QPDFArgParser.hh>
 
 #include <qpdf/QIntC.hh>
+#include <qpdf/QPDFLogger.hh>
 #include <qpdf/QPDFUsage.hh>
 #include <qpdf/QTC.hh>
 #include <qpdf/QUtil.hh>
@@ -235,7 +236,7 @@ QPDFArgParser::argCompletionZsh()
 void
 QPDFArgParser::argHelp(std::string const& p)
 {
-    std::cout << getHelp(p);
+    QPDFLogger::defaultLogger()->info(getHelp(p));
     exit(0);
 }
 

libqpdf/QPDFJob_argv.cc

@@ -14,6 +14,7 @@
 #include <qpdf/QPDFArgParser.hh>
 #include <qpdf/QPDFCryptoProvider.hh>
 #include <qpdf/QPDFJob.hh>
+#include <qpdf/QPDFLogger.hh>
 #include <qpdf/QTC.hh>
 #include <qpdf/QUtil.hh>
 
@@ -104,10 +105,10 @@ void
 ArgParser::argVersion()
 {
     auto whoami = this->ap.getProgname();
-    std::cout << whoami << " version " << QPDF::QPDFVersion() << std::endl
-              << "Run " << whoami
-              << " --copyright to see copyright and license information."
-              << std::endl;
+    *QPDFLogger::defaultLogger()->getInfo()
+        << whoami << " version " << QPDF::QPDFVersion() << "\n"
+        << "Run " << whoami
+        << " --copyright to see copyright and license information.\n";
 }
 
 void
@@ -117,48 +118,35 @@ ArgParser::argCopyright()
     // Make sure the output looks right on an 80-column display.
     //               1         2         3         4         5         6         7         8
     //      12345678901234567890123456789012345678901234567890123456789012345678901234567890
-    std::cout
+    *QPDFLogger::defaultLogger()->getInfo()
         << this->ap.getProgname()
-        << " version " << QPDF::QPDFVersion() << std::endl
-        << std::endl
-        << "Copyright (c) 2005-2022 Jay Berkenbilt"
-        << std::endl
-        << "QPDF is licensed under the Apache License, Version 2.0 (the \"License\");"
-        << std::endl
-        << "you may not use this file except in compliance with the License."
-        << std::endl
-        << "You may obtain a copy of the License at"
-        << std::endl
-        << std::endl
-        << "  http://www.apache.org/licenses/LICENSE-2.0"
-        << std::endl
-        << std::endl
-        << "Unless required by applicable law or agreed to in writing, software"
-        << std::endl
-        << "distributed under the License is distributed on an \"AS IS\" BASIS,"
-        << std::endl
-        << "WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied."
-        << std::endl
-        << "See the License for the specific language governing permissions and"
-        << std::endl
-        << "limitations under the License."
-        << std::endl
-        << std::endl
-        << "Versions of qpdf prior to version 7 were released under the terms"
-        << std::endl
-        << "of version 2.0 of the Artistic License. At your option, you may"
-        << std::endl
-        << "continue to consider qpdf to be licensed under those terms. Please"
-        << std::endl
-        << "see the manual for additional information."
-        << std::endl;
+        << " version " << QPDF::QPDFVersion() << "\n"
+        << "\n"
+        << "Copyright (c) 2005-2022 Jay Berkenbilt\n"
+        << "QPDF is licensed under the Apache License, Version 2.0 (the \"License\");\n"
+        << "you may not use this file except in compliance with the License.\n"
+        << "You may obtain a copy of the License at\n"
+        << "\n"
+        << "  http://www.apache.org/licenses/LICENSE-2.0\n"
+        << "\n"
+        << "Unless required by applicable law or agreed to in writing, software\n"
+        << "distributed under the License is distributed on an \"AS IS\" BASIS,\n"
+        << "WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.\n"
+        << "See the License for the specific language governing permissions and\n"
+        << "limitations under the License.\n"
+        << "\n"
+        << "Versions of qpdf prior to version 7 were released under the terms\n"
+        << "of version 2.0 of the Artistic License. At your option, you may\n"
+        << "continue to consider qpdf to be licensed under those terms. Please\n"
+        << "see the manual for additional information.\n";
     // clang-format on
 }
 
 void
 ArgParser::argJsonHelp()
 {
-    std::cout << QPDFJob::json_out_schema_v1() << std::endl;
+    *QPDFLogger::defaultLogger()->getInfo()
+        << QPDFJob::json_out_schema_v1() << "\n";
 }
 
 void
@@ -166,10 +154,10 @@ ArgParser::argShowCrypto()
 {
     auto crypto = QPDFCryptoProvider::getRegisteredImpls();
     std::string default_crypto = QPDFCryptoProvider::getDefaultProvider();
-    std::cout << default_crypto << std::endl;
+    *QPDFLogger::defaultLogger()->getInfo() << default_crypto << "\n";
     for (auto const& iter: crypto) {
         if (iter != default_crypto) {
-            std::cout << iter << std::endl;
+            *QPDFLogger::defaultLogger()->getInfo() << iter << "\n";
         }
     }
 }
@@ -407,7 +395,8 @@ ArgParser::argEndCopyAttachment()
 void
 ArgParser::argJobJsonHelp()
 {
-    std::cout << QPDFJob::job_json_schema_v1() << std::endl;
+    *QPDFLogger::defaultLogger()->getInfo()
+        << QPDFJob::job_json_schema_v1() << "\n";
 }
 
 void

libqpdf/QPDFJob_config.cc

@@ -1,5 +1,6 @@
 #include <qpdf/QPDFJob.hh>
 
+#include <qpdf/QPDFLogger.hh>
 #include <qpdf/QTC.hh>
 #include <qpdf/QUtil.hh>
 
@@ -648,9 +649,10 @@ QPDFJob::Config::passwordFile(std::string const& parameter)
         o.m->password = QUtil::make_shared_cstr(lines.front());
 
         if (lines.size() > 1) {
-            std::cerr << this->o.m->message_prefix
-                      << ": WARNING: all but the first line of"
-                      << " the password file are ignored" << std::endl;
+            *QPDFLogger::defaultLogger()->getError()
+                << this->o.m->message_prefix
+                << ": WARNING: all but the first line of"
+                << " the password file are ignored\n";
         }
     }
     return this;

libqpdf/QPDFObjectHandle.cc

@@ -5,6 +5,7 @@
 #include <qpdf/Pl_QPDFTokenizer.hh>
 #include <qpdf/QPDF.hh>
 #include <qpdf/QPDFExc.hh>
+#include <qpdf/QPDFLogger.hh>
 #include <qpdf/QPDFMatrix.hh>
 #include <qpdf/QPDFPageObjectHelper.hh>
 #include <qpdf/QPDF_Array.hh>
@@ -578,13 +579,12 @@ QPDFObjectHandle::getIntValueAsInt()
     if (v < INT_MIN) {
         QTC::TC("qpdf", "QPDFObjectHandle int returning INT_MIN");
         warnIfPossible(
-            "requested value of integer is too small; returning INT_MIN",
-            false);
+            "requested value of integer is too small; returning INT_MIN");
         result = INT_MIN;
     } else if (v > INT_MAX) {
         QTC::TC("qpdf", "QPDFObjectHandle int returning INT_MAX");
         warnIfPossible(
-            "requested value of integer is too big; returning INT_MAX", false);
+            "requested value of integer is too big; returning INT_MAX");
         result = INT_MAX;
     } else {
         result = static_cast<int>(v);
@@ -610,7 +610,7 @@ QPDFObjectHandle::getUIntValue()
     if (v < 0) {
         QTC::TC("qpdf", "QPDFObjectHandle uint returning 0");
         warnIfPossible(
-            "unsigned value request for negative number; returning 0", false);
+            "unsigned value request for negative number; returning 0");
     } else {
         result = static_cast<unsigned long long>(v);
     }
@@ -635,15 +635,12 @@ QPDFObjectHandle::getUIntValueAsUInt()
     if (v < 0) {
         QTC::TC("qpdf", "QPDFObjectHandle uint uint returning 0");
         warnIfPossible(
-            "unsigned integer value request for negative number; returning 0",
-            false);
+            "unsigned integer value request for negative number; returning 0");
         result = 0;
     } else if (v > UINT_MAX) {
         QTC::TC("qpdf", "QPDFObjectHandle uint returning UINT_MAX");
-        warnIfPossible(
-            "requested value of unsigned integer is too big;"
-            " returning UINT_MAX",
-            false);
+        warnIfPossible("requested value of unsigned integer is too big;"
+                       " returning UINT_MAX");
         result = UINT_MAX;
     } else {
         result = static_cast<unsigned int>(v);
@@ -3000,16 +2997,15 @@ QPDFObjectHandle::typeWarning(
 }
 
 void
-QPDFObjectHandle::warnIfPossible(
-    std::string const& warning, bool throw_if_no_description)
+QPDFObjectHandle::warnIfPossible(std::string const& warning)
 {
     QPDF* context = 0;
     std::string description;
     dereference();
     if (this->obj->getDescription(context, description)) {
         warn(context, QPDFExc(qpdf_e_damaged_pdf, "", description, 0, warning));
-    } else if (throw_if_no_description) {
-        throw std::runtime_error(warning);
+    } else {
+        *QPDFLogger::defaultLogger()->getError() << warning << "\n";
     }
 }
 

libqpdf/qpdf-c.cc

@@ -6,6 +6,7 @@
 #include <qpdf/Pl_Discard.hh>
 #include <qpdf/QIntC.hh>
 #include <qpdf/QPDFExc.hh>
+#include <qpdf/QPDFLogger.hh>
 #include <qpdf/QPDFWriter.hh>
 #include <qpdf/QTC.hh>
 #include <qpdf/QUtil.hh>
@@ -185,8 +186,9 @@ qpdf_cleanup(qpdf_data* qpdf)
     qpdf_oh_release_all(*qpdf);
     if ((*qpdf)->error.get()) {
         QTC::TC("qpdf", "qpdf-c cleanup warned about unhandled error");
-        std::cerr << "WARNING: application did not handle error: "
-                  << (*qpdf)->error->what() << std::endl;
+        *QPDFLogger::defaultLogger()->getWarn()
+            << "WARNING: application did not handle error: "
+            << (*qpdf)->error->what() << "\n";
     }
     delete *qpdf;
     *qpdf = 0;
@@ -898,7 +900,8 @@ trap_oh_errors(
                     " to ERROR HANDLING in qpdf-c.h"));
                 qpdf->oh_error_occurred = true;
             }
-            std::cerr << qpdf->error->what() << std::endl;
+            *QPDFLogger::defaultLogger()->getError()
+                << qpdf->error->what() << "\n";
         }
         return fallback();
     }

libqpdf/qpdfjob-c.cc

@@ -1,6 +1,7 @@
 #include <qpdf/qpdfjob-c.h>
 
 #include <qpdf/QPDFJob.hh>
+#include <qpdf/QPDFLogger.hh>
 #include <qpdf/QPDFUsage.hh>
 #include <qpdf/QUtil.hh>
 
@@ -19,7 +20,8 @@ qpdfjob_run_from_argv(char const* const argv[])
         j.initializeFromArgv(argv);
         j.run();
     } catch (std::exception& e) {
-        std::cerr << whoami << ": " << e.what() << std::endl;
+        *QPDFLogger::defaultLogger()->getError()
+            << whoami << ": " << e.what() << "\n";
         return QPDFJob::EXIT_ERROR;
     }
     return j.getExitCode();
@@ -48,7 +50,8 @@ qpdfjob_run_from_json(char const* json)
         j.initializeFromJson(json);
         j.run();
     } catch (std::exception& e) {
-        std::cerr << "qpdfjob json: " << e.what() << std::endl;
+        *QPDFLogger::defaultLogger()->getError()
+            << "qpdfjob json: " << e.what() << "\n";
         return QPDFJob::EXIT_ERROR;
     }
     return j.getExitCode();

manual/release-notes.rst

@@ -120,6 +120,11 @@ For a detailed list of changes, please see the file
       - See :ref:`breaking-crypto-api` for specific details, and see
         :ref:`weak-crypto` for a general discussion.
 
+    - QPDFObjectHandle::warnIfPossible no longer takes an optional
+      argument to throw an exception if there is no description. If
+      there is no description, it writes to the default logger's error
+      stream.
+
   - CLI Enhancements
 
     - ``qpdf --list-attachments --verbose`` include some additional
@@ -139,6 +144,20 @@ For a detailed list of changes, please see the file
 
   - Library Enhancements
 
+    - A new object ``QPDFLogger`` has been added. Details are in
+      :file:`include/qpdf/QPDFLogger.hh`.
+
+      - ``QPDF`` and ``QPDFJob`` both use the default logger by
+        default but can have their loggers overridden. The
+        ``setOutputStreams`` method is deprecated in both classes.
+
+      - A few things from ``QPDFObjectHandle`` that used to be
+        exceptions now write errors with the default logger.
+
+      - By configuring the default logger, it is possible to capture
+        output and errors that slipped through the cracks with
+        ``setOutputStreams``.
+
     - New methods ``insertItemAndGet``, ``appendItemAndGet``,
       ``eraseItemAndGet``, ``replaceKeyAndGet``, and
       ``removeKeyAndGet`` return the newly added or removed object.

qpdf/qtest/error-condition.test

@@ -111,11 +111,11 @@ $td->runtest("C API: no recovery",
 
 $td->runtest("integer type checks",
              {$td->COMMAND => "test_driver 62 minimal.pdf"},
-             {$td->STRING => "test 62 done\n", $td->EXIT_STATUS => 0},
+             {$td->FILE => "test62.out", $td->EXIT_STATUS => 0},
              $td->NORMALIZE_NEWLINES);
 $td->runtest("getValueAs... accessor checks",
              {$td->COMMAND => "test_driver 85 -"},
-             {$td->STRING => "test 85 done\n", $td->EXIT_STATUS => 0},
+             {$td->FILE => "test85.out", $td->EXIT_STATUS => 0},
              $td->NORMALIZE_NEWLINES);
 
 $n_tests += @badfiles + 11;

qpdf/qtest/qpdf/test62.out

@@ -0,0 +1,7 @@
+requested value of integer is too big; returning INT_MAX
+requested value of unsigned integer is too big; returning UINT_MAX
+unsigned value request for negative number; returning 0
+requested value of integer is too small; returning INT_MIN
+unsigned integer value request for negative number; returning 0
+requested value of integer is too big; returning INT_MAX
+test 62 done

qpdf/qtest/qpdf/test85.out

@@ -0,0 +1,6 @@
+requested value of integer is too big; returning INT_MAX
+requested value of integer is too small; returning INT_MIN
+unsigned value request for negative number; returning 0
+unsigned integer value request for negative number; returning 0
+requested value of unsigned integer is too big; returning UINT_MAX
+test 85 done