vim-patch:9.1.1823: diff: w_topline may be invalidated (#36018)

Problem:  diff: w_topline may be invalidated
Solution: Update lnum in diff_set_topline()
          (Yee Cheng Chin).

This can happen in ex_diffupdate() for certain edge cases which cause
the logic to now be wrong. This was also the root cause for vim/vim#18437 where
Vim would crash due to a null pointer dereferencing (said pointer would
not be null under normal circumstances).

related: vim/vim#18437
closes: vim/vim#18484

dd9ed46a39

Co-authored-by: Yee Cheng Chin <ychin.git@gmail.com>
This commit is contained in:
zeertzjq
2025-10-04 19:50:51 +08:00
committed by GitHub
parent 94bd212dbc
commit 0fca343d64

View File

@@ -2052,7 +2052,9 @@ static void calculate_topfill_and_topline(const int fromidx, const int toidx, co
// move the same amount of virtual lines in the target buffer to find the
// cursor's line number
int curlinenum_to = thistopdiff != NULL ? thistopdiff->df_lnum[toidx] : 1;
int curlinenum_to
= thistopdiff != NULL // this should not be null, but just for safety
? thistopdiff->df_lnum[toidx] : 1;
int virt_lines_left = virtual_lines_passed;
curdif = thistopdiff;
@@ -2466,7 +2468,6 @@ static int diff_cmp(char *s1, char *s2)
void diff_set_topline(win_T *fromwin, win_T *towin)
{
buf_T *frombuf = fromwin->w_buffer;
linenr_T lnum = fromwin->w_topline;
int fromidx = diff_buf_idx(frombuf, curtab);
if (fromidx == DB_COUNT) {
@@ -2478,6 +2479,7 @@ void diff_set_topline(win_T *fromwin, win_T *towin)
// update after a big change
ex_diffupdate(NULL);
}
linenr_T lnum = fromwin->w_topline;
towin->w_topfill = 0;
// search for a change that includes "lnum" in the list of diffblocks.