gcc/doc/gcc/gcc-command-options/options-controlling-the-preprocessor.rst

   1 ..
   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.
   5
   6 .. index:: preprocessor options, options, preprocessor
   7
   8 .. _preprocessor-options:
   9
  10 Options Controlling the Preprocessor
  11 ************************************
  12
  13 These options control the C preprocessor, which is run on each C source
  14 file before actual compilation.
  15
  16 If you use the :option:`-E` option, nothing is done except preprocessing.
  17 Some of these options make sense only together with :option:`-E` because
  18 they cause the preprocessor output to be unsuitable for actual
  19 compilation.
  20
  21 In addition to the options listed here, there are a number of options
  22 to control search paths for include files documented in
  23 :ref:`directory-options`.
  24 Options to control preprocessor diagnostics are listed in
  25 :ref:`warning-options`.
  26
  27 .. include:: ../../../../doc/cppopts.rst
  28
  29
  30 .. option:: -Wp,option
  31
  32   You can use :option:`-Wp,option` to bypass the compiler driver
  33   and pass :samp:`{option}` directly through to the preprocessor.  If
  34   :samp:`{option}` contains commas, it is split into multiple options at the
  35   commas.  However, many options are modified, translated or interpreted
  36   by the compiler driver before being passed to the preprocessor, and
  37   :option:`-Wp` forcibly bypasses this phase.  The preprocessor's direct
  38   interface is undocumented and subject to change, so whenever possible
  39   you should avoid using :option:`-Wp` and let the driver handle the
  40   options instead.
  41
  42 .. option:: -Xpreprocessor {option}
  43
  44   Pass :samp:`{option}` as an option to the preprocessor.  You can use this to
  45   supply system-specific preprocessor options that GCC does not
  46   recognize.
  47
  48   If you want to pass an option that takes an argument, you must use
  49   :option:`-Xpreprocessor` twice, once for the option and once for the argument.
  50
  51 .. option:: -no-integrated-cpp
  52
  53   Perform preprocessing as a separate pass before compilation.
  54   By default, GCC performs preprocessing as an integrated part of
  55   input tokenization and parsing.
  56   If this option is provided, the appropriate language front end
  57   (:command:`cc1`, :command:`cc1plus`, or :command:`cc1obj` for C, C++,
  58   and Objective-C, respectively) is instead invoked twice,
  59   once for preprocessing only and once for actual compilation
  60   of the preprocessed input.
  61   This option may be useful in conjunction with the :option:`-B` or
  62   :option:`-wrapper` options to specify an alternate preprocessor or
  63   perform additional processing of the program source between
  64   normal preprocessing and compilation.
  65
  66 .. option:: -flarge-source-files
  67
  68   Adjust GCC to expect large source files, at the expense of slower
  69   compilation and higher memory usage.
  70
  71   Specifically, GCC normally tracks both column numbers and line numbers
  72   within source files and it normally prints both of these numbers in
  73   diagnostics.  However, once it has processed a certain number of source
  74   lines, it stops tracking column numbers and only tracks line numbers.
  75   This means that diagnostics for later lines do not include column numbers.
  76   It also means that options like :option:`-Wmisleading-indentation` cease to work
  77   at that point, although the compiler prints a note if this happens.
  78   Passing :option:`-flarge-source-files` significantly increases the number
  79   of source lines that GCC can process before it stops tracking columns.