Fix line-number-at-pos when POSITION is out of narrowing

* src/fns.c (Fline_number_at_pos): Don't signal an error when
ABSOLUTE is nil and POSITION is outside of the narrowing, like the
original Lisp implementation did.  Minor speedup by using the byte
position where it is available from the get-go.  (Bug#62857)

1 files changed, 23 insertions, 12 deletions

diff --git a/src/fns.c b/src/fns.c
index ff364c65e26..e8cd6211d6d 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -6116,29 +6116,40 @@ second optional argument ABSOLUTE is non-nil, the value counts the lines
 from the absolute start of the buffer, disregarding the narrowing.  */)
   (register Lisp_Object position, Lisp_Object absolute)
 {
-  ptrdiff_t pos, start = BEGV_BYTE;
+  ptrdiff_t pos_byte, start_byte = BEGV_BYTE;
 
   if (MARKERP (position))
-    pos = marker_position (position);
+    {
+      /* We don't trust the byte position if the marker's buffer is
+         not the current buffer.  */
+      if (XMARKER (position)->buffer != current_buffer)
+	pos_byte = CHAR_TO_BYTE (marker_position (position));
+      else
+	pos_byte = marker_byte_position (position);
+    }
   else if (NILP (position))
-    pos = PT;
+    pos_byte = PT_BYTE;
   else
     {
       CHECK_FIXNUM (position);
-      pos = XFIXNUM (position);
+      ptrdiff_t pos = XFIXNUM (position);
+      /* Check that POSITION is valid. */
+      if (pos < BEG || pos > Z)
+	args_out_of_range_3 (position, make_int (BEG), make_int (Z));
+      pos_byte = CHAR_TO_BYTE (pos);
     }
 
   if (!NILP (absolute))
-    start = BEG_BYTE;
+    start_byte = BEG_BYTE;
+  else if (NILP (absolute))
+    pos_byte = clip_to_bounds (BEGV_BYTE, pos_byte, ZV_BYTE);
 
-  /* Check that POSITION is in the accessible range of the buffer, or,
-     if we're reporting absolute positions, in the buffer. */
-  if (NILP (absolute) && (pos < BEGV || pos > ZV))
-    args_out_of_range_3 (make_int (pos), make_int (BEGV), make_int (ZV));
-  else if (!NILP (absolute) && (pos < 1 || pos > Z))
-    args_out_of_range_3 (make_int (pos), make_int (1), make_int (Z));
+  /* Check that POSITION is valid. */
+  if (pos_byte < BEG_BYTE || pos_byte > Z_BYTE)
+    args_out_of_range_3 (make_int (BYTE_TO_CHAR (pos_byte)),
+			 make_int (BEG), make_int (Z));
 
-  return make_int (count_lines (start, CHAR_TO_BYTE (pos)) + 1);
+  return make_int (count_lines (start_byte, pos_byte) + 1);
 }