[Emacs-diffs] emacs-26 9a1329e: Avoid crashes with very wide TTY frames on MS-Windows

[Eli Zaretskii]

branch: emacs-26
commit 9a1329e966ecbd22464f607456153bdd4fa0d5ea
Author: Eli Zaretskii <address@hidden>
Commit: Eli Zaretskii <address@hidden>

    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)
---
 src/w32console.c | 30 ++++++++++++++++++++++++++----
 1 file changed, 26 insertions(+), 4 deletions(-)

diff --git a/src/w32console.c b/src/w32console.c
index ea30853..36a6ced 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