[gdb/tui] Fix resizing of terminal to 1 or 2 lines

When starting TUI in a terminal with 3 lines:
...
$ echo $LINES
3
$ gdb -q -tui
...
and resizing the terminal to 2 lines we run into a segfault.

The problem is that for the source window:
- the minimum height is 3 (the default), but
- the maximum height is only 2 because there are only 2 lines.

This discrepancy eventually leads to a call to newwin in make_window with:
...
(gdb) p height
$1 = 3
(gdb) p width
$2 = 56
(gdb) p y
$3 = -1
(gdb) p x
$4 = 0
...
which results in a nullptr.

This violates the assumption here in tui_apply_current_layout:
....
  /* Get the new list of currently visible windows.  */
  std::vector<tui_win_info *> new_tui_windows;
  applied_layout->get_windows (&new_tui_windows);
...
that get_windows only returns visible windows, which leads to tui_windows
holding a dangling pointer, which results in the segfault.

Fix this by:
- making sure get_windows only returns visible windows, and
- detecting the situation and dropping windows from the layout if
  there's no room for them.

Tested on x86_64-linux.

Approved-By: Tom Tromey <tom@tromey.com>
PR tui/31044
Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=31044

diff --git a/gdb/testsuite/gdb.tui/resize.exp b/gdb/testsuite/gdb.tui/resize.exp
index 60d5116886b07eaba6bf93d59531bac887d5f349..e15f8a2f507ded9f7d7af420d0a4df6179dc8988 100644 (file)
--- a/gdb/testsuite/gdb.tui/resize.exp
+++ b/gdb/testsuite/gdb.tui/resize.exp
@@ -39,3 +39,12 @@ Term::check_contents "source at startup" "\\|.*21 *return 0"
 
 Term::resize 40 90
 Term::check_box "source box after resize" 0 0 90 26
+
+# Check that resizing to less than 3 lines doesn't cause problems.
+foreach lines { 2 1 } {
+    with_test_prefix lines=$lines {
+       Term::resize $lines 90 0
+       Term::wait_for ""
+       Term::check_region_contents "has prompt" 0 0 90 $lines "$gdb_prompt"
+    }
+}

diff --git a/gdb/tui/tui-layout.c b/gdb/tui/tui-layout.c
index b932649b3ac2f51502fbd8006bc065108af51d4f..85f4991c769d5c93f401873160d94f4cd8b4fe2f 100644 (file)
--- a/gdb/tui/tui-layout.c
+++ b/gdb/tui/tui-layout.c
@@ -452,6 +452,13 @@ tui_layout_window::apply (int x_, int y_, int width_, int height_,
   width = width_;
   height = height_;
   gdb_assert (m_window != nullptr);
+  if (width == 0 || height == 0)
+    {
+      /* The window was dropped, so it's going to be deleted, reset the
+        soon to be dangling pointer.  */
+      m_window = nullptr;
+      return;
+    }
   m_window->resize (height, width, x, y);
 }
 
@@ -833,6 +840,7 @@ tui_layout_split::apply (int x_, int y_, int width_, int height_,
   int available_size = m_vertical ? height : width;
   int last_index = -1;
   int total_weight = 0;
+  int prev = -1;
   for (int i = 0; i < m_splits.size (); ++i)
     {
       bool cmd_win_already_exists = TUI_CMD_WIN != nullptr;
@@ -864,6 +872,14 @@ tui_layout_split::apply (int x_, int y_, int width_, int height_,
          info[i].max_size = info[i].min_size;
        }
 
+      if (info[i].min_size > info[i].max_size)
+       {
+         /* There is not enough room for this window, drop it.  */
+         info[i].min_size = 0;
+         info[i].max_size = 0;
+         continue;
+       }
+
       if (info[i].min_size == info[i].max_size)
        available_size -= info[i].min_size;
       else
@@ -874,10 +890,12 @@ tui_layout_split::apply (int x_, int y_, int width_, int height_,
 
       /* Two adjacent boxed windows will share a border, making a bit
         more size available.  */
-      if (i > 0
-         && m_splits[i - 1].layout->last_edge_has_border_p ()
+      if (prev != -1
+         && m_splits[prev].layout->last_edge_has_border_p ()
          && m_splits[i].layout->first_edge_has_border_p ())
        info[i].share_box = true;
+
+      prev = i;
     }
 
   /* If last_index is set then we have a window that is not of a fixed

diff --git a/gdb/tui/tui-layout.h b/gdb/tui/tui-layout.h
index a6d34851bef4a47e28977cc87d53fbddec15121b..4d29c0570ac1faf49752f0b1a5817129f0cbe3d5 100644 (file)
--- a/gdb/tui/tui-layout.h
+++ b/gdb/tui/tui-layout.h
@@ -189,7 +189,11 @@ public:
   /* See tui_layout_base::get_windows.  */
   void get_windows (std::vector<tui_win_info *> *windows) override
   {
-    windows->push_back (m_window);
+    if (m_window != nullptr && m_window->is_visible ())
+      {
+       /* Only get visible windows.  */
+       windows->push_back (m_window);
+      }
   }
 
 protected: