Fix latent bug in tui_copy_source_line

tui_copy_source_line has a bug, where it can advance past the
terminating \0 in its input string.  This patch fixes the bug and adds
a test case for this function.

gdb/ChangeLog
2019-12-01  Tom Tromey  <tom@tromey.com>

	* tui/tui-winsource.c (tui_copy_source_line): Don't advance past
	\0.
	* unittests/tui-selftests.c: New file.
	* Makefile.in (SUBDIR_UNITTESTS_SRCS): Add tui-selftests.c.

Change-Id: I46cdabe6e57549983149b8f640cda5edd16fa260

4 files changed, 58 insertions, 0 deletions

diff --git a/gdb/ChangeLog b/gdb/ChangeLog
index 67b76dc..e61b08b 100644
--- a/gdb/ChangeLog
+++ b/gdb/ChangeLog
@@ -1,5 +1,12 @@
 2019-12-01  Tom Tromey  <tom@tromey.com>
 
+	* tui/tui-winsource.c (tui_copy_source_line): Don't advance past
+	\0.
+	* unittests/tui-selftests.c: New file.
+	* Makefile.in (SUBDIR_UNITTESTS_SRCS): Add tui-selftests.c.
+
+2019-12-01  Tom Tromey  <tom@tromey.com>
+
 	* tui/tui.c (tui_enable): Call tui_update_variables earlier.
 
 2019-12-01  Tom Tromey  <tom@tromey.com>
diff --git a/gdb/Makefile.in b/gdb/Makefile.in
index 58f5f93..e5c8faa 100644
--- a/gdb/Makefile.in
+++ b/gdb/Makefile.in
@@ -442,6 +442,7 @@ SUBDIR_UNITTESTS_SRCS = \
 	unittests/string_view-selftests.c \
 	unittests/style-selftests.c \
 	unittests/tracepoint-selftests.c \
+	unittests/tui-selftests.c \
 	unittests/unpack-selftests.c \
 	unittests/utils-selftests.c \
 	unittests/vec-utils-selftests.c \
diff --git a/gdb/tui/tui-winsource.c b/gdb/tui/tui-winsource.c
index 81937c1..6653709 100644
--- a/gdb/tui/tui-winsource.c
+++ b/gdb/tui/tui-winsource.c
@@ -103,6 +103,8 @@ tui_copy_source_line (const char **ptr, int line_no, int first_col,
 	  lineptr += skip_bytes;
 	  continue;
 	}
+      if (c == '\0')
+	break;
 
       ++lineptr;
       ++column;
diff --git a/gdb/unittests/tui-selftests.c b/gdb/unittests/tui-selftests.c
new file mode 100644
index 0000000..3a5d34f
--- /dev/null
+++ b/gdb/unittests/tui-selftests.c
@@ -0,0 +1,48 @@
+/* Self tests for the TUI
+
+   Copyright (C) 2019 Free Software Foundation, Inc.
+
+   This file is part of GDB.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "defs.h"
+#include "gdbsupport/selftest.h"
+#include "tui/tui-winsource.h"
+
+namespace selftests {
+namespace tui {
+
+static void
+run_tests ()
+{
+  const char *text = "hello";
+  std::string result = tui_copy_source_line (&text, 0, 0, 50, 0);
+  SELF_CHECK (result == "hello");
+  SELF_CHECK (*text == '\0');
+
+  text = "hello\n";
+  result = tui_copy_source_line (&text, 0, 0, 3, 0);
+  SELF_CHECK (result == "hel");
+  SELF_CHECK (*text == '\0');
+}
+
+} /* namespace tui*/
+} /* namespace selftests */
+
+void
+_initialize_tui_selftest ()
+{
+  selftests::register_test ("tui", selftests::tui::run_tests);
+}