Avoid crashes with very wide TTY frames on MS-Windows

* src/w32console.c <glyph_base>: Reduce the number of elements
to 80.
<glyphs, glyphs_len>: New static variables.
(w32con_clear_end_of_line): If the line is wider than the
current size of the "empty row" in 'glyphs', reallocate
'glyphs' to support the full width of the frame.  This
avoids segfaults when the frame is wider than 256 columns.
(Bug#32445)

1 files changed, 26 insertions, 4 deletions

diff --git a/src/w32console.c b/src/w32console.c
index ea30853bade..36a6ced2983 100644
--- a/src/w32console.c
+++ b/src/w32console.c
@@ -140,23 +140,36 @@ w32con_clear_frame (struct frame *f)
 }
 
 
-static struct glyph glyph_base[256];
+static struct glyph glyph_base[80];
+static struct glyph *glyphs = glyph_base;
+static size_t glyphs_len = ARRAYELTS (glyph_base);
 static BOOL  ceol_initialized = FALSE;
 
 /* Clear from Cursor to end (what's "standout marker"?).  */
 static void
 w32con_clear_end_of_line (struct frame *f, int end)
 {
+  /* Time to reallocate our "empty row"?  With today's large screens,
+     it is not unthinkable to see TTY frames well in excess of
+     80-character width.  */
+  if (end - cursor_coords.X > glyphs_len)
+    {
+      if (glyphs == glyph_base)
+        glyphs = NULL;
+      glyphs = xrealloc (glyphs, FRAME_COLS (f) * sizeof (struct glyph));
+      glyphs_len = FRAME_COLS (f);
+      ceol_initialized = FALSE;
+    }
   if (!ceol_initialized)
     {
       int i;
-      for (i = 0; i < 256; i++)
+      for (i = 0; i < glyphs_len; i++)
         {
-          memcpy (&glyph_base[i], &space_glyph, sizeof (struct glyph));
+          memcpy (&glyphs[i], &space_glyph, sizeof (struct glyph));
         }
       ceol_initialized = TRUE;
     }
-  w32con_write_glyphs (f, glyph_base, end - cursor_coords.X);   /* fencepost ?  */
+  w32con_write_glyphs (f, glyphs, end - cursor_coords.X);
 }
 
 /* Insert n lines at vpos. if n is negative delete -n lines.  */
@@ -772,6 +785,15 @@ initialize_w32_display (struct terminal *term, int *width, int *height)
       *width = 1 + info.srWindow.Right - info.srWindow.Left;
     }
 
+  /* Force reinitialization of the "empty row" buffer, in case they
+     dumped from a running session.  */
+  if (glyphs != glyph_base)
+    {
+      glyphs = NULL;
+      glyphs_len = 0;
+      ceol_initialized = FALSE;
+    }
+
   if (os_subtype == OS_NT)
     w32_console_unicode_input = 1;
   else