..
  Copyright 1988-2022 Free Software Foundation, Inc.
  This is part of the GCC manual.
  For copying conditions, see the copyright.rst file.

.. index:: escaped newlines, newlines (escaped)

.. _escaped-newlines:

Slightly Looser Rules for Escaped Newlines
******************************************

The preprocessor treatment of escaped newlines is more relaxed 
than that specified by the C90 standard, which requires the newline
to immediately follow a backslash.  
GCC's implementation allows whitespace in the form
of spaces, horizontal and vertical tabs, and form feeds between the
backslash and the subsequent newline.  The preprocessor issues a
warning, but treats it as a valid escaped newline and combines the two
lines to form a single logical line.  This works within comments and
tokens, as well as between tokens.  Comments are *not* treated as
whitespace for the purposes of this relaxation, since they have not
yet been replaced with spaces.