1 files changed, 37 insertions, 11 deletions

diff --git a/src/nvim/diff.c b/src/nvim/diff.c
index f1dd08f0e6..68441f7adc 100644
--- a/src/nvim/diff.c
+++ b/src/nvim/diff.c
@@ -44,6 +44,7 @@
 #include "nvim/mbyte.h"
 #include "nvim/mbyte_defs.h"
 #include "nvim/memline.h"
+#include "nvim/memline_defs.h"
 #include "nvim/memory.h"
 #include "nvim/message.h"
 #include "nvim/move.h"
@@ -1621,6 +1622,11 @@ static void process_hunk(diff_T **dpp, diff_T **dprevp, int idx_orig, int idx_ne
     } else {
       // second overlap of new block with existing block
       dp->df_count[idx_new] += (linenr_T)hunk->count_new;
+      if ((dp->df_lnum[idx_new] + dp->df_count[idx_new] - 1)
+          > curtab->tp_diffbuf[idx_new]->b_ml.ml_line_count) {
+        dp->df_count[idx_new] = curtab->tp_diffbuf[idx_new]->b_ml.ml_line_count
+                                - dp->df_lnum[idx_new] + 1;
+      }
     }
 
     // Adjust the size of the block to include all the lines to the
@@ -1631,6 +1637,11 @@ static void process_hunk(diff_T **dpp, diff_T **dprevp, int idx_orig, int idx_ne
     if (off < 0) {
       // new change ends in existing block, adjust the end
       dp->df_count[idx_new] += -off;
+      if ((dp->df_lnum[idx_new] + dp->df_count[idx_new] - 1)
+          > curtab->tp_diffbuf[idx_new]->b_ml.ml_line_count) {
+        dp->df_count[idx_new] = curtab->tp_diffbuf[idx_new]->b_ml.ml_line_count
+                                - dp->df_lnum[idx_new] + 1;
+      }
       off = 0;
     }
 
@@ -1809,7 +1820,8 @@ static void find_top_diff_block(diff_T **thistopdiff, diff_T **nextblockblock, i
       topdiffchange = 0;
     }
 
-    // check if the fromwin topline is matched by the current diff. if so, set it to the top of the diff block
+    // check if the fromwin topline is matched by the current diff. if so,
+    // set it to the top of the diff block
     if (topline >= topdiff->df_lnum[fromidx] && topline <=
         (topdiff->df_lnum[fromidx] + topdiff->df_count[fromidx])) {
       // this line is inside the current diff block, so we will save the
@@ -1854,8 +1866,10 @@ static void count_filler_lines_and_topline(int *curlinenum_to, int *linesfiller,
       }
     } else {
       (*linesfiller) = 0;
-      ch_virtual_lines = get_max_diff_length(curdif);
-      isfiller = (curdif->df_count[toidx] ? false : true);
+      if (curdif) {
+        ch_virtual_lines = get_max_diff_length(curdif);
+        isfiller = (curdif->df_count[toidx] ? false : true);
+      }
       if (isfiller) {
         while (curdif && curdif->df_next && curdif->df_lnum[toidx] ==
                curdif->df_next->df_lnum[toidx]
@@ -2010,10 +2024,15 @@ static void run_linematch_algorithm(diff_T *dp)
   size_t ndiffs = 0;
   for (int i = 0; i < DB_COUNT; i++) {
     if (curtab->tp_diffbuf[i] != NULL) {
-      // write the contents of the entire buffer to
-      // diffbufs_mm[diffbuffers_count]
-      diff_write_buffer(curtab->tp_diffbuf[i], &diffbufs_mm[ndiffs],
-                        dp->df_lnum[i], dp->df_lnum[i] + dp->df_count[i] - 1);
+      if (dp->df_count[i] > 0) {
+        // write the contents of the entire buffer to
+        // diffbufs_mm[diffbuffers_count]
+        diff_write_buffer(curtab->tp_diffbuf[i], &diffbufs_mm[ndiffs],
+                          dp->df_lnum[i], dp->df_lnum[i] + dp->df_count[i] - 1);
+      } else {
+        diffbufs_mm[ndiffs].size = 0;
+        diffbufs_mm[ndiffs].ptr = NULL;
+      }
 
       diffbufs[ndiffs] = &diffbufs_mm[ndiffs];
 
@@ -2049,6 +2068,12 @@ static void run_linematch_algorithm(diff_T *dp)
 /// Returns > 0 for inserting that many filler lines above it (never happens
 /// when 'diffopt' doesn't contain "filler").
 /// This should only be used for windows where 'diff' is set.
+/// When diffopt contains linematch, a changed/added/deleted line
+/// may also have filler lines above it. In such a case, the possibilities
+/// are no longer mutually exclusive. The number of filler lines is
+/// returned from diff_check, and the integer 'linestatus' passed by
+/// pointer is set to -1 to indicate a changed line, and -2 to indicate an
+/// added line
 ///
 /// @param wp
 /// @param lnum
@@ -2102,7 +2127,8 @@ int diff_check_with_linestatus(win_T *wp, linenr_T lnum, int *linestatus)
   // Useful for scrollbind calculations which need to count all the filler lines
   // above the screen.
   if (lnum >= wp->w_topline && lnum < wp->w_botline
-      && !dp->is_linematched && diff_linematch(dp)) {
+      && !dp->is_linematched && diff_linematch(dp)
+      && diff_check_sanity(curtab, dp)) {
     run_linematch_algorithm(dp);
   }
 
@@ -2417,7 +2443,7 @@ int diffopt_changed(void)
 
   char *p = p_dip;
   while (*p != NUL) {
-    // Note: Keep this in sync with p_dip_values
+    // Note: Keep this in sync with opt_dip_values.
     if (strncmp(p, "filler", 6) == 0) {
       p += 6;
       diff_flags_new |= DIFF_FILLER;
@@ -2464,7 +2490,7 @@ int diffopt_changed(void)
       p += 8;
       diff_flags_new |= DIFF_INTERNAL;
     } else if (strncmp(p, "algorithm:", 10) == 0) {
-      // Note: Keep this in sync with p_dip_algorithm_values.
+      // Note: Keep this in sync with opt_dip_algorithm_values.
       p += 10;
       if (strncmp(p, "myers", 5) == 0) {
         p += 5;
@@ -2745,7 +2771,7 @@ bool diff_infold(win_T *wp, linenr_T lnum)
 void nv_diffgetput(bool put, size_t count)
 {
   if (bt_prompt(curbuf)) {
-    vim_beep(BO_OPER);
+    vim_beep(kOptBoFlagOperator);
     return;
   }