buffer: don't rely on curbuf in BUFEMPTY

src/nvim/buffer.c

@@ -139,7 +139,7 @@ read_buffer(
   if (read_stdin) {
     // Set or reset 'modified' before executing autocommands, so that
     // it can be changed there.
-    if (!readonlymode && !BUFEMPTY()) {
+    if (!readonlymode && !BUFEMPTY(curbuf)) {
       changed();
     } else if (retval != FAIL) {
       unchanged(curbuf, false, true);
@@ -1921,7 +1921,7 @@ bool curbuf_reusable(void)
   return (curbuf != NULL
           && curbuf->b_ffname == NULL
           && curbuf->b_nwindows <= 1
-          && (curbuf->b_ml.ml_mfp == NULL || BUFEMPTY())
+          && (curbuf->b_ml.ml_mfp == NULL || BUFEMPTY(curbuf))
           && !bt_quickfix(curbuf)
           && !curbufIsChanged());
 }
@@ -2061,7 +2061,7 @@ int buflist_getfile(int n, linenr_T lnum, int options, int forceit)
     // If 'switchbuf' contains "split", "vsplit" or "newtab" and the
     // current buffer isn't empty: open new tab or window
     if (wp == NULL && (swb_flags & (SWB_VSPLIT | SWB_SPLIT | SWB_NEWTAB))
-        && !BUFEMPTY()) {
+        && !BUFEMPTY(curbuf)) {
       if (swb_flags & SWB_NEWTAB) {
         tabpage_new();
       } else if (win_split(0, (swb_flags & SWB_VSPLIT) ? WSP_VERT : 0)
@@ -4951,7 +4951,7 @@ do_arg_all(
   win_enter(lastwin, false);
   // ":tab drop file" should re-use an empty window to avoid "--remote-tab"
   // leaving an empty tab page when executed locally.
-  if (keep_tabs && BUFEMPTY() && curbuf->b_nwindows == 1
+  if (keep_tabs && BUFEMPTY(curbuf) && curbuf->b_nwindows == 1
       && curbuf->b_ffname == NULL && !curbuf->b_changed) {
     use_firstwin = true;
     tab_drop_empty_window = true;

src/nvim/diff.c

@@ -2669,7 +2669,7 @@ void ex_diffgetput(exarg_T *eap)
         }
       }
 
-      buf_empty = BUFEMPTY();
+      buf_empty = BUFEMPTY(curbuf);
       added = 0;
 
       for (i = 0; i < count; ++i) {

src/nvim/edit.c

@@ -8047,7 +8047,7 @@ static bool ins_bs(int c, int mode, int *inserted_space_p)
   // can't backup past first character in buffer
   // can't backup past starting point unless 'backspace' > 1
   // can backup to a previous line if 'backspace' == 0
-  if (BUFEMPTY()
+  if (BUFEMPTY(curbuf)
       || (!revins_on
           && ((curwin->w_cursor.lnum == 1 && curwin->w_cursor.col == 0)
               || (!can_bs(BS_START)

src/nvim/fileio.c

@@ -5027,7 +5027,7 @@ void buf_reload(buf_T *buf, int orig_mode)
   // buffer contents.  But if reading the file fails we should keep
   // the old contents.  Can't use memory only, the file might be
   // too big.  Use a hidden buffer to move the buffer contents to.
-  if (BUFEMPTY() || saved == FAIL) {
+  if (BUFEMPTY(curbuf) || saved == FAIL) {
     savebuf = NULL;
   } else {
     // Allocate a buffer without putting it in the buffer list.
@@ -5060,7 +5060,7 @@ void buf_reload(buf_T *buf, int orig_mode)
       if (savebuf != NULL && bufref_valid(&bufref) && buf == curbuf) {
         // Put the text back from the save buffer.  First
         // delete any lines that readfile() added.
-        while (!BUFEMPTY()) {
+        while (!BUFEMPTY(curbuf)) {
           if (ml_delete(buf->b_ml.ml_line_count, false) == FAIL) {
             break;
           }

src/nvim/macros.h

@@ -35,8 +35,8 @@
 #define LINEEMPTY(p) (*ml_get(p) == NUL)
 
 /// BUFEMPTY() - return TRUE if the current buffer is empty
-#define BUFEMPTY() (curbuf->b_ml.ml_line_count == 1 && *ml_get((linenr_T)1) == \
-                    NUL)
+#define BUFEMPTY(buf) ((buf)->b_ml.ml_line_count == 1 \
+                       && *ml_get_buf((buf), (linenr_T)1, false) == '\0')
 
 // toupper() and tolower() that use the current locale.
 // Careful: Only call TOUPPER_LOC() and TOLOWER_LOC() with a character in the

src/nvim/main.c

@@ -1444,11 +1444,9 @@ static void read_stdin(void)
   no_wait_return = true;
   int save_msg_didany = msg_didany;
   set_buflisted(true);
-
   // Create memfile and read from stdin.
   (void)open_buffer(true, NULL, 0);
-
-  if (BUFEMPTY() && curbuf->b_next != NULL) {
+  if (BUFEMPTY(curbuf) && curbuf->b_next != NULL) {
     // stdin was empty, go to buffer 2 (e.g. "echo file1 | xargs nvim"). #8561
     do_cmdline_cmd("silent! bnext");
     // Delete the empty stdin buffer.

src/nvim/move.c

@@ -172,7 +172,7 @@ void update_topline(win_T *wp)
   old_topfill = wp->w_topfill;
 
   // If the buffer is empty, always set topline to 1.
-  if (BUFEMPTY()) {             // special case - file is empty
+  if (BUFEMPTY(curbuf)) {             // special case - file is empty
     if (wp->w_topline != 1) {
       redraw_later(wp, NOT_VALID);
     }

src/nvim/ops.c

@@ -3069,7 +3069,7 @@ void do_put(int regname, yankreg_T *reg, int dir, long count, int flags)
     }
     // In an empty buffer the empty line is going to be replaced, include
     // it in the saved lines.
-    if ((BUFEMPTY() ? u_save(0, 2) : u_save(lnum - 1, lnum)) == FAIL) {
+    if ((BUFEMPTY(curbuf) ? u_save(0, 2) : u_save(lnum - 1, lnum)) == FAIL) {
       goto end;
     }
     if (dir == FORWARD) {

src/nvim/option.c

@@ -880,7 +880,7 @@ void set_init_3(void)
     xfree(p);
   }
 
-  if (BUFEMPTY()) {
+  if (BUFEMPTY(curbuf)) {
     int idx_ffs = findoption_len(S_LEN("ffs"));
 
     // Apply the first entry of 'fileformats' to the initial buffer.

src/nvim/popupmnu.c

@@ -735,7 +735,7 @@ static int pum_set_selected(int n, int repeat)
             && (curbuf->b_p_bt[2] == 'f')
             && (curbuf->b_p_bh[0] == 'w')) {
           // Already a "wipeout" buffer, make it empty.
-          while (!BUFEMPTY()) {
+          while (!BUFEMPTY(curbuf)) {
             ml_delete((linenr_T)1, false);
           }
         } else {

src/nvim/spell.c

@@ -6672,7 +6672,7 @@ void ex_spelldump(exarg_T *eap)
   set_option_value("spl",  dummy, (char *)spl, OPT_LOCAL);
   xfree(spl);
 
-  if (!BUFEMPTY()) {
+  if (!BUFEMPTY(curbuf)) {
     return;
   }
 

src/nvim/undo.c

@@ -2414,7 +2414,7 @@ static void u_undoredo(int undo, bool do_buf_event)
 
   curhead->uh_entry = newlist;
   curhead->uh_flags = new_flags;
-  if ((old_flags & UH_EMPTYBUF) && BUFEMPTY()) {
+  if ((old_flags & UH_EMPTYBUF) && BUFEMPTY(curbuf)) {
     curbuf->b_ml.ml_flags |= ML_EMPTY;
   }
   if (old_flags & UH_CHANGED) {

src/nvim/version.c

@@ -2190,7 +2190,7 @@ void list_version(void)
 /// Show the intro message when not editing a file.
 void maybe_intro_message(void)
 {
-  if (BUFEMPTY()
+  if (BUFEMPTY(curbuf)
       && (curbuf->b_fname == NULL)
       && (firstwin->w_next == NULL)
       && (vim_strchr(p_shm, SHM_INTRO) == NULL)) {