vim-patch:8.2.1787: crash with 'incsearch' and very long line

Problem:    Crash with 'incsearch' and very long line.
Solution:   Check whether regprog becomes NULL. (closes vim/vim#7063)
795aaa1e84

N/A patches for version.c:

vim-patch:8.2.1784: commits are not scanned for security problems

Problem:    commits are not scanned for security problems
Solution:   Enable Github code scanning. (Christian Brabandt, closes vim/vim#7057)
fa79be6b10

src/nvim/search.c

@@ -651,6 +651,10 @@ int searchit(
         colnr_T col = at_first_line && (options & SEARCH_COL) ? pos->col : 0;
         nmatched = vim_regexec_multi(&regmatch, win, buf,
                                      lnum, col, tm, timed_out);
+        // vim_regexec_multi() may clear "regprog"
+        if (regmatch.regprog == NULL) {
+          break;
+        }
         // Abort searching on an error (e.g., out of stack).
         if (called_emsg || (timed_out != NULL && *timed_out)) {
           break;
@@ -722,6 +726,10 @@ int searchit(
                 match_ok = false;
                 break;
               }
+              // vim_regexec_multi() may clear "regprog"
+              if (regmatch.regprog == NULL) {
+                break;
+              }
               matchpos = regmatch.startpos[0];
               endpos = regmatch.endpos[0];
               submatch = first_submatch(&regmatch);
@@ -811,10 +819,13 @@ int searchit(
                   }
                   break;
               }
-
+              // vim_regexec_multi() may clear "regprog"
-              /* Need to get the line pointer again, a
+              if (regmatch.regprog == NULL) {
-               * multi-line search may have made it invalid. */
+                break;
-              ptr = ml_get_buf(buf, lnum + matchpos.lnum, FALSE);
+              }
+              // Need to get the line pointer again, a
+              // multi-line search may have made it invalid.
+              ptr = ml_get_buf(buf, lnum + matchpos.lnum, false);
             }
 
             /*
@@ -891,6 +902,11 @@ int searchit(
       }
       at_first_line = FALSE;
 
+      // vim_regexec_multi() may clear "regprog"
+      if (regmatch.regprog == NULL) {
+        break;
+      }
+
       // Stop the search if wrapscan isn't set, "stop_lnum" is
       // specified, after an interrupt, after a match and after looping
       // twice.
@@ -4243,7 +4259,8 @@ is_zero_width(char_u *pattern, int move, pos_T *cur, Direction direction)
       if (nmatched != 0) {
         break;
       }
-    } while (direction == FORWARD
+    } while (regmatch.regprog != NULL
+             && direction == FORWARD
              ? regmatch.startpos[0].col < pos.col
              : regmatch.startpos[0].col > pos.col);
 

src/nvim/testdir/test_search.vim

@@ -981,6 +981,21 @@ func Test_incsearch_substitute()
   call Incsearch_cleanup()
 endfunc
 
+func Test_incsearch_substitute_long_line()
+  throw 'skipped: Nvim does not support test_override()'
+  new
+  call test_override("char_avail", 1)
+  set incsearch
+
+  call repeat('x', 100000)->setline(1)
+  call feedkeys(':s/\%c', 'xt')
+  redraw
+  call feedkeys("\<Esc>", 'xt')
+
+  call Incsearch_cleanup()
+  bwipe!
+endfunc
+
 func Test_search_undefined_behaviour()
   if !has("terminal")
     return