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bug#8227: possibly uninitialized variables in update_window_fringes
From: |
YAMAMOTO Mitsuharu |
Subject: |
bug#8227: possibly uninitialized variables in update_window_fringes |
Date: |
Fri, 11 Mar 2011 10:31:27 +0900 |
User-agent: |
Wanderlust/2.14.0 (Africa) SEMI/1.14.6 (Maruoka) FLIM/1.14.8 (Shijō) APEL/10.6 Emacs/22.3 (sparc-sun-solaris2.8) MULE/5.0 (SAKAKI) |
>>>>> On Thu, 10 Mar 2011 15:45:19 -0800, Paul Eggert <eggert@cs.ucla.edu> said:
> I found this problem by compiling Emacs with GCC's -Wuninitialized flag.
> The following code in the Emacs trunk src/fringe.c's
> update_window_fringes function might be using uninitialized
> variables:
> int top_row_ends_at_zv_p, bot_row_ends_at_zv_p;
> ...
> if (top_ind_rn >= 0)
> {
> ...
> top_row_ends_at_zv_p = row->ends_at_zv_p;
> }
> ...
> for (y = w->vscroll, rn = 0;
> y < yb && rn < nrows;
> y += row->height, rn++)
> {
> ...
> if (WINDOW_LEFT_FRINGE_WIDTH (w) == 0)
> ...
> else if (row->left_user_fringe_bitmap != NO_FRINGE_BITMAP)
> ...
> else if ((!row->reversed_p && row->truncated_on_left_p)
> || (row->reversed_p && row->truncated_on_right_p))
> ...
> else if (row->indicate_bob_p && EQ (boundary_top, Qleft))
> {
> left = ((row->indicate_eob_p && EQ (boundary_bot, Qleft))
> ? LEFT_FRINGE (1, Qtop_bottom, top_row_ends_at_zv_p)
> : LEFT_FRINGE (2, Qtop, 0));
> ...
> }
> The last assignment uses top_row_ends_at_zv_p, but it's not clear
> from the previous tests that top_row_ends_at_zv_p must be initialized.
> There is a similar issue with bot_row_ends_at_zv_p.
No problem. top_ind_rn is set to a non-negative value whenever
row->indicate_bob_p is set.
for (y = w->vscroll, rn = 0;
y < yb && rn < nrows;
y += row->height, ++rn)
{
...
if (!row->mode_line_p)
{
if (top_ind_rn < 0 && row->visible_height > 0)
{
if (MATRIX_ROW_START_CHARPOS (row) <= BUF_BEGV (XBUFFER
(w->buffer))
&& !MATRIX_ROW_PARTIALLY_VISIBLE_AT_TOP_P (w, row))
row->indicate_bob_p = !NILP (boundary_top);
else
row->indicate_top_line_p = !NILP (arrow_top);
top_ind_rn = rn;
}
YAMAMOTO Mitsuharu
mituharu@math.s.chiba-u.ac.jp