gcc/doc/gcc/extensions-to-the-c-language-family/slightly-looser-rules-for-escaped-newlines.rst

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   2   Copyright 1988-2022 Free Software Foundation, Inc.
   3   This is part of the GCC manual.
   4   For copying conditions, see the copyright.rst file.
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   6 .. index:: escaped newlines, newlines (escaped)
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   8 .. _escaped-newlines:
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  10 Slightly Looser Rules for Escaped Newlines
  11 ******************************************
  12
  13 The preprocessor treatment of escaped newlines is more relaxed
  14 than that specified by the C90 standard, which requires the newline
  15 to immediately follow a backslash.
  16 GCC's implementation allows whitespace in the form
  17 of spaces, horizontal and vertical tabs, and form feeds between the
  18 backslash and the subsequent newline.  The preprocessor issues a
  19 warning, but treats it as a valid escaped newline and combines the two
  20 lines to form a single logical line.  This works within comments and
  21 tokens, as well as between tokens.  Comments are *not* treated as
  22 whitespace for the purposes of this relaxation, since they have not
  23 yet been replaced with spaces.