[pushed] [gdb/tui] Fix length of status line string

[Tom de Vries <tdevries@suse.de>]

In commit 5d10a2041eb ("gdb: add string_file::release method") this was added:
...
+  std::string string_val = string.release ();
...
without updating subsequent uses of string.size (), which returns 0 after the
string.release () call.

Fix this by:
- using string_val.size () instead of string.size (), and
- adding an assert that would have caught this regression.

Tested on x86_64-linux.

Reviewed-By: Simon Marchi <simon.marchi@efficios.com>
PR tui/30389
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30389
---
 gdb/tui/tui-stack.c | 11 +++++++----
 1 file changed, 7 insertions(+), 4 deletions(-)

diff --git a/gdb/tui/tui-stack.c b/gdb/tui/tui-stack.c
index 0a750187c26..76b8f066abb 100644
--- a/gdb/tui/tui-stack.c
+++ b/gdb/tui/tui-stack.c
@@ -183,10 +183,13 @@ tui_locator_window::make_status_line () const
 
   std::string string_val = string.release ();
 
-  if (string.size () < status_size)
-    string_val.append (status_size - string.size (), ' ');
-  else if (string.size () > status_size)
-    string_val.erase (status_size, string.size ());
+  size_t len = string_val.size ();
+  if (len < status_size)
+    string_val.append (status_size - len, ' ');
+  else if (len > status_size)
+    string_val.erase (status_size, len);
+
+  gdb_assert (string_val.size () == status_size);
 
   return string_val;
 }

base-commit: 3ad6c165ca098a0fa4491893a75b4b1581698484
-- 
2.35.3