Better error message when trying to backup a DB to itself

src/burp/burp.cpp

@@ -1025,6 +1025,11 @@ int gbak(Firebird::UtilSvc* uSvc)
 				BURP_error(334, true, SafeArg() << in_sw_tab->in_sw_name);
 			tdgbl->gbl_sw_direct_io = true;
 			break;
+		case IN_SW_BURP_OVERWRITE:
+			if (tdgbl->gbl_sw_backup_overwrite)
+				BURP_error(334, true, SafeArg() << in_sw_tab->in_sw_name);
+			tdgbl->gbl_sw_backup_overwrite = true;
+			break;
 		case IN_SW_BURP_E:
 			if (!tdgbl->gbl_sw_compress)
 				BURP_error(334, true, SafeArg() << in_sw_tab->in_sw_name);
@@ -1162,21 +1167,23 @@ int gbak(Firebird::UtilSvc* uSvc)
 		Firebird::PathName expanded;
 		expandDatabaseName(file->fil_name, expanded, NULL);
 
+		const bool isSource = (file->fil_name.c_str() == file1);
+
 		for (file_list = file->fil_next; file_list;
 			 file_list = file_list->fil_next)
 		{
-			if (file->fil_name == file_list->fil_name || expanded == file_list->fil_name)
-			{
-				BURP_error(9, true);
-				// msg 9 mutiple sources or destinations specified
-			}
-
 			Firebird::PathName expanded2;
 			expandDatabaseName(file_list->fil_name, expanded2, NULL);
-			if (file->fil_name == expanded2 || expanded == expanded2)
+
+			if (file->fil_name == file_list->fil_name || expanded == file_list->fil_name ||
+				file->fil_name == expanded2 || expanded == expanded2)
 			{
-				BURP_error(9, true);
-				// msg 9 mutiple sources or destinations specified
+				if (isSource)
+					BURP_error(11, true);
+					// msg 11 input and output have the same name.  Disallowed.
+				else
+					BURP_error(9, true);
+					// msg 9 mutiple sources or destinations specified
 			}
 		}
 
@@ -2216,15 +2223,29 @@ static gbak_action open_files(const TEXT* file1,
 			{
 				Firebird::string nm = tdgbl->toSystem(fil->fil_name);
 #ifdef WIN_NT
-				if ((fil->fil_fd = NT_tape_open(nm.c_str(), MODE_WRITE, CREATE_ALWAYS)) == INVALID_HANDLE_VALUE)
+				if ((fil->fil_fd = NT_tape_open(nm.c_str(), MODE_WRITE,
+					tdgbl->gbl_sw_backup_overwrite ? CREATE_ALWAYS : CREATE_NEW)) == INVALID_HANDLE_VALUE)
 #else
-				const int wmode = MODE_WRITE | (tdgbl->gbl_sw_direct_io ? O_DIRECT : 0);
+				const int wmode = MODE_WRITE
+					| (tdgbl->gbl_sw_direct_io ? O_DIRECT : 0)
+					| (tdgbl->gbl_sw_backup_overwrite ? 0 : O_EXCL);
 				if ((fil->fil_fd = open(fil->fil_name.c_str(), wmode, open_mask)) == -1)
 #endif // WIN_NT
 				{
-
-					BURP_error(65, false, fil->fil_name.c_str());
-					// msg 65 can't open backup file %s
+#ifdef WIN_NT
+					if (GetLastError() == ERROR_FILE_EXISTS)
+#else
+					if (errno == EEXIST)
+#endif // WIN_NT
+					{
+						BURP_error(424, false, fil->fil_name.c_str());
+						// msg 424 backup file %s already exists, use -OVERWRITE to replace
+					}
+					else
+					{
+						BURP_error(65, false, fil->fil_name.c_str());
+						// msg 65 can't open backup file %s
+					}
 					flag = QUIT;
 					break;
 				}

src/burp/burp.h

@@ -1061,6 +1061,7 @@ class BurpGlobals : public Firebird::ThreadData, public GblPool
 	bool		gbl_sw_mode_val;
 	bool		gbl_sw_overwrite;
 	bool		gbl_sw_direct_io;
+	bool		gbl_sw_backup_overwrite;
 	bool		gbl_sw_zip;
 	const SCHAR*	gbl_sw_keyholder;
 	const SCHAR*	gbl_sw_crypt;

src/burp/burpswi.h

@@ -104,6 +104,7 @@ inline constexpr int IN_SW_BURP_DIRECT_IO			= 55;	// direct IO for backup files
 
 inline constexpr int IN_SW_BURP_SKIP_SCHEMA_DATA	= 56;	// skip data from schema
 inline constexpr int IN_SW_BURP_INCLUDE_SCHEMA_DATA	= 57;	// backup data from schemas
+inline constexpr int IN_SW_BURP_OVERWRITE			= 58;	// allow overwriting existing backup file
 
 /**************************************************************************/
 
@@ -170,6 +171,8 @@ static inline constexpr Switches::in_sw_tab_t reference_burp_in_sw_table[] =
 				// msg 99: @1ONE_AT_A_TIME restore one relation at a time
 	{IN_SW_BURP_OL,	isc_spb_bkp_old_descriptions, "OLD_DESCRIPTIONS", 0, 0, 0, false, true,	186, 2, NULL, boBackup},
 				// msg 186: @1OLD_DESCRIPTIONS save old style metadata descriptions
+	{IN_SW_BURP_OVERWRITE, 0,					"OVERWRITE",		0, 0, 0, false, true,	423,	2, NULL, boBackup},
+			// msg 423: @1OV(ERWRITE) allow overwriting existing backup file(s)
 	{IN_SW_BURP_P,	isc_spb_res_page_size,		"PAGE_SIZE",		0, 0, 0, false, false,	101,	1, NULL, boRestore},
 				// msg 101: @1PAGE_SIZE override default page size
 	{IN_SW_BURP_PARALLEL_WORKERS, isc_spb_bkp_parallel_workers, "PARALLEL", 0, 0, 0, false, false, 406, 3, NULL, boGeneral},

src/burp/mvol.cpp

@@ -1548,17 +1548,38 @@ static DESC next_volume( DESC handle, ULONG mode, bool full_buffer)
 		prompt_for_name(new_file, sizeof(new_file));
 
 #ifdef WIN_NT
-		new_desc = NT_tape_open(new_file, mode, OPEN_ALWAYS);
+		if (mode == MODE_WRITE)
+		{
+			new_desc = NT_tape_open(new_file, mode,
+				tdgbl->gbl_sw_backup_overwrite ? CREATE_ALWAYS : CREATE_NEW);
+		}
+		else
+			new_desc = NT_tape_open(new_file, mode, OPEN_ALWAYS);
 		if (new_desc == INVALID_HANDLE_VALUE)
 #else
 		ULONG mode2 = mode;
-		if (mode == MODE_WRITE && tdgbl->gbl_sw_direct_io)
-			mode2 |= O_DIRECT;
+		if (mode == MODE_WRITE)
+		{
+			if (tdgbl->gbl_sw_direct_io)
+				mode2 |= O_DIRECT;
+			if (!tdgbl->gbl_sw_backup_overwrite)
+				mode2 |= O_EXCL;
+		}
 
 		new_desc = open(new_file, mode2, open_mask);
 		if (new_desc < 0)
 #endif // WIN_NT
 		{
+#ifdef WIN_NT
+			if (mode == MODE_WRITE && GetLastError() == ERROR_FILE_EXISTS)
+#else
+			if (mode == MODE_WRITE && errno == EEXIST)
+#endif // WIN_NT
+			{
+				BURP_print(true, 424, new_file);
+				// msg 424 backup file %s already exists, use -OVERWRITE to replace
+				continue;
+			}
 			BURP_print(true, 222, new_file);
 			// msg 222 \n\nCould not open file name \"%s\"\n
 			continue;

src/include/firebird/impl/msg/gbak.h

@@ -418,3 +418,5 @@ FB_IMPL_MSG_NO_SYMBOL(GBAK, 419, "regular expression to skip schemas was already
 FB_IMPL_MSG_NO_SYMBOL(GBAK, 420, "regular expression to include schemas was already set")
 FB_IMPL_MSG_SYMBOL(GBAK, 421, gbak_plugin_schema_migration, "migrating @1 plugin objects to schema @2")
 FB_IMPL_MSG_SYMBOL(GBAK, 422, gbak_plugin_schema_migration_err, "error migrating @1 plugin objects to schema @2. Plugin objects will be in inconsistent state:")
+FB_IMPL_MSG_NO_SYMBOL(GBAK, 423, "    @1OV(ERWRITE)          allow overwriting existing backup file(s)")
+FB_IMPL_MSG(GBAK, 424, gbak_backup_file_exists, -901, "00", "000", "backup file @1 already exists, use -OVERWRITE to replace")