vim-patch:7.4.251

Problem:  Crash when BufAdd autocommand wipes out the buffer.

Solution: Check for buffer to still be valid. Postpone freeing the
          buffer structure. (Hirohito Higashi)

https://code.google.com/p/vim/source/detail?r=29eb4c2a33ac701bfcd4d2e2bed7864eba876e0e

src/buffer.c

@@ -550,7 +550,14 @@ static void free_buffer(buf_T *buf)
   free_buffer_stuff(buf, TRUE);
   unref_var_dict(buf->b_vars);
   aubuflocal_remove(buf);
-  vim_free(buf);
+  if (autocmd_busy) {
+    // Do not free the buffer structure while autocommands are executing,
+    // it's still needed. Free it when autocmd_busy is reset.
+    buf->b_next = au_pending_free_buf;
+    au_pending_free_buf = buf;
+  } else {
+    vim_free(buf);
+  }
 }
 
 /*
@@ -1332,8 +1339,12 @@ buflist_new (
     buf_copy_options(buf, 0);
     if ((flags & BLN_LISTED) && !buf->b_p_bl) {
       buf->b_p_bl = TRUE;
-      if (!(flags & BLN_DUMMY))
+      if (!(flags & BLN_DUMMY)) {
         apply_autocmds(EVENT_BUFADD, NULL, NULL, FALSE, buf);
+        if (!buf_valid(buf)) {
+          return NULL;
+        }
+      }
     }
     return buf;
   }
@@ -1469,8 +1480,15 @@ buflist_new (
   buf->b_p_bl = (flags & BLN_LISTED) ? TRUE : FALSE;    /* init 'buflisted' */
   if (!(flags & BLN_DUMMY)) {
     apply_autocmds(EVENT_BUFNEW, NULL, NULL, FALSE, buf);
-    if (flags & BLN_LISTED)
+    if (!buf_valid(buf)) {
+      return NULL;
+    }
+    if (flags & BLN_LISTED) {
       apply_autocmds(EVENT_BUFADD, NULL, NULL, FALSE, buf);
+      if (!buf_valid(buf)) {
+        return NULL;
+      }
+    }
     if (aborting())             /* autocmds may abort script processing */
       return NULL;
   }

src/ex_cmds.c

@@ -2774,6 +2774,11 @@ do_ecmd (
       }
       buf = buflist_new(ffname, sfname, 0L,
           BLN_CURBUF | ((flags & ECMD_SET_HELP) ? 0 : BLN_LISTED));
+      // Autocmds may change curwin and curbuf.
+      if (oldwin != NULL) {
+        oldwin = curwin;
+      }
+      old_curbuf = curbuf;
     }
     if (buf == NULL)
       goto theend;

src/fileio.c

@@ -7525,14 +7525,17 @@ apply_autocmds_group (
   vim_free(sfname);
   --nesting;            /* see matching increment above */
 
-  /*
-   * When stopping to execute autocommands, restore the search patterns and
-   * the redo buffer.
-   */
+  // When stopping to execute autocommands, restore the search patterns and
+  // the redo buffer.  Free buffers in the au_pending_free_buf list.
   if (!autocmd_busy) {
     restore_search_patterns();
     restoreRedobuff();
     did_filetype = FALSE;
+    while (au_pending_free_buf != NULL) {
+      buf_T *b = au_pending_free_buf->b_next;
+      vim_free(au_pending_free_buf);
+      au_pending_free_buf = b;
+    }
   }
 
   /*

src/globals.h

@@ -352,6 +352,11 @@ EXTERN int keep_filetype INIT(= FALSE);         /* value for did_filetype when
  * which one is preferred, au_new_curbuf is set to it */
 EXTERN buf_T    *au_new_curbuf INIT(= NULL);
 
+// When deleting the buffer and autocmd_busy is TRUE, do not free the buffer
+// but link it in the list starting with au_pending_free_buf, using b_next.
+// Free the buffer when autocmd_busy is set to FALSE.
+EXTERN buf_T *au_pending_free_buf INIT(= NULL);
+
 /*
  * Mouse coordinates, set by check_termcode()
  */

src/version.c

@@ -209,7 +209,7 @@ static int included_patches[] = {
   //254,
   //253,
   //252,
-  //251,
+  251,
   //250,
   //249,
   //248,