more tweaking of C error interface

git-svn-id: svn+q:///qpdf/trunk@894 71b93d88-0707-0410-a8cf-f5a4172ac649

include/qpdf/Constants.h

@@ -17,7 +17,8 @@
 
 enum qpdf_error_code_e
 {
-    qpdf_e_internal = 1, 	/* logic/programming error -- indicates bug */
+    qpdf_e_success = 0,
+    qpdf_e_internal,	 	/* logic/programming error -- indicates bug */
     qpdf_e_system,		/* I/O error, memory error, etc. */
     qpdf_e_unsupported,		/* PDF feature not (yet) supported by qpdf */
     qpdf_e_password,		/* incorrect password for encrypted file */

include/qpdf/qpdf-c.h

@@ -142,8 +142,7 @@ extern "C" {
     char const* qpdf_get_error_full_text(qpdf_data q, qpdf_error e);
 
     /* Use these functions to extract individual fields from the
-     * error; see QPDFExc.hh for details.  It is invalid for e to be a
-     * null pointer for any of these calls. */
+     * error; see QPDFExc.hh for details. */
     QPDF_DLL
     enum qpdf_error_code_e qpdf_get_error_code(qpdf_data q, qpdf_error e);
     QPDF_DLL

libqpdf/qpdf-c.cc

@@ -166,26 +166,46 @@ qpdf_error qpdf_next_warning(qpdf_data qpdf)
 
 char const* qpdf_get_error_full_text(qpdf_data qpdf, qpdf_error e)
 {
+    if (e == 0)
+    {
+	return "";
+    }
     return e->exc.getPointer()->what();
 }
 
 enum qpdf_error_code_e qpdf_get_error_code(qpdf_data qpdf, qpdf_error e)
 {
+    if (e == 0)
+    {
+	return qpdf_e_success;
+    }
     return e->exc.getPointer()->getErrorCode();
 }
 
 char const* qpdf_get_error_filename(qpdf_data qpdf, qpdf_error e)
 {
+    if (e == 0)
+    {
+	return "";
+    }
     return e->exc.getPointer()->getFilename().c_str();
 }
 
 unsigned long qpdf_get_error_file_position(qpdf_data qpdf, qpdf_error e)
 {
+    if (e == 0)
+    {
+	return 0;
+    }
     return e->exc.getPointer()->getFilePosition();
 }
 
 char const* qpdf_get_error_message_detail(qpdf_data qpdf, qpdf_error e)
 {
+    if (e == 0)
+    {
+	return "";
+    }
     return e->exc.getPointer()->getMessageDetail().c_str();
 }
 

qpdf/qpdf-ctest.c

@@ -18,15 +18,24 @@ static void report_errors()
 	printf("  pos : %ld\n", qpdf_get_error_file_position(qpdf, e));
 	printf("  text: %s\n", qpdf_get_error_message_detail(qpdf, e));
     }
+    e = qpdf_get_error(qpdf);
     if (qpdf_has_error(qpdf))
     {
-	e = qpdf_get_error(qpdf);
 	printf("error: %s\n", qpdf_get_error_full_text(qpdf, e));
 	printf("  code: %d\n", qpdf_get_error_code(qpdf, e));
 	printf("  file: %s\n", qpdf_get_error_filename(qpdf, e));
 	printf("  pos : %ld\n", qpdf_get_error_file_position(qpdf, e));
 	printf("  text: %s\n", qpdf_get_error_message_detail(qpdf, e));
     }
+    else
+    {
+	assert(e == 0);
+	assert(qpdf_get_error_code(qpdf, e) == qpdf_e_success);
+	(void)qpdf_get_error_full_text(qpdf, e);
+	(void)qpdf_get_error_filename(qpdf, e);
+	(void)qpdf_get_error_file_position(qpdf, e);
+	(void)qpdf_get_error_message_detail(qpdf, e);
+    }
 }
 
 static void test01(char const* infile,