1@c Copyright (C) 1999-2017 Free Software Foundation, Inc. 2@c This is part of the CPP and GCC manuals. 3@c For copying conditions, see the file gcc.texi. 4 5@c --------------------------------------------------------------------- 6@c Options affecting include directory search in the preprocessor 7@c --------------------------------------------------------------------- 8 9@c If this file is included with the flag ``cppmanual'' set, it is 10@c formatted for inclusion in the CPP manual; otherwise the main GCC manual. 11 12@item -I @var{dir} 13@itemx -iquote @var{dir} 14@itemx -isystem @var{dir} 15@itemx -idirafter @var{dir} 16@opindex I 17@opindex iquote 18@opindex isystem 19@opindex idirafter 20Add the directory @var{dir} to the list of directories to be searched 21for header files during preprocessing. 22@ifset cppmanual 23@xref{Search Path}. 24@end ifset 25If @var{dir} begins with @samp{=}, then the @samp{=} is replaced 26by the sysroot prefix; see @option{--sysroot} and @option{-isysroot}. 27 28Directories specified with @option{-iquote} apply only to the quote 29form of the directive, @code{@w{#include "@var{file}"}}. 30Directories specified with @option{-I}, @option{-isystem}, 31or @option{-idirafter} apply to lookup for both the 32@code{@w{#include "@var{file}"}} and 33@code{@w{#include <@var{file}>}} directives. 34 35You can specify any number or combination of these options on the 36command line to search for header files in several directories. 37The lookup order is as follows: 38 39@enumerate 40@item 41For the quote form of the include directive, the directory of the current 42file is searched first. 43 44@item 45For the quote form of the include directive, the directories specified 46by @option{-iquote} options are searched in left-to-right order, 47as they appear on the command line. 48 49@item 50Directories specified with @option{-I} options are scanned in 51left-to-right order. 52 53@item 54Directories specified with @option{-isystem} options are scanned in 55left-to-right order. 56 57@item 58Standard system directories are scanned. 59 60@item 61Directories specified with @option{-idirafter} options are scanned in 62left-to-right order. 63@end enumerate 64 65You can use @option{-I} to override a system header 66file, substituting your own version, since these directories are 67searched before the standard system header file directories. 68However, you should 69not use this option to add directories that contain vendor-supplied 70system header files; use @option{-isystem} for that. 71 72The @option{-isystem} and @option{-idirafter} options also mark the directory 73as a system directory, so that it gets the same special treatment that 74is applied to the standard system directories. 75@ifset cppmanual 76@xref{System Headers}. 77@end ifset 78 79If a standard system include directory, or a directory specified with 80@option{-isystem}, is also specified with @option{-I}, the @option{-I} 81option is ignored. The directory is still searched but as a 82system directory at its normal position in the system include chain. 83This is to ensure that GCC's procedure to fix buggy system headers and 84the ordering for the @code{#include_next} directive are not inadvertently 85changed. 86If you really need to change the search order for system directories, 87use the @option{-nostdinc} and/or @option{-isystem} options. 88@ifset cppmanual 89@xref{System Headers}. 90@end ifset 91 92@item -I- 93@opindex I- 94Split the include path. 95This option has been deprecated. Please use @option{-iquote} instead for 96@option{-I} directories before the @option{-I-} and remove the @option{-I-} 97option. 98 99Any directories specified with @option{-I} 100options before @option{-I-} are searched only for headers requested with 101@code{@w{#include "@var{file}"}}; they are not searched for 102@code{@w{#include <@var{file}>}}. If additional directories are 103specified with @option{-I} options after the @option{-I-}, those 104directories are searched for all @samp{#include} directives. 105 106In addition, @option{-I-} inhibits the use of the directory of the current 107file directory as the first search directory for @code{@w{#include 108"@var{file}"}}. There is no way to override this effect of @option{-I-}. 109@ifset cppmanual 110@xref{Search Path}. 111@end ifset 112 113@item -iprefix @var{prefix} 114@opindex iprefix 115Specify @var{prefix} as the prefix for subsequent @option{-iwithprefix} 116options. If the prefix represents a directory, you should include the 117final @samp{/}. 118 119@item -iwithprefix @var{dir} 120@itemx -iwithprefixbefore @var{dir} 121@opindex iwithprefix 122@opindex iwithprefixbefore 123Append @var{dir} to the prefix specified previously with 124@option{-iprefix}, and add the resulting directory to the include search 125path. @option{-iwithprefixbefore} puts it in the same place @option{-I} 126would; @option{-iwithprefix} puts it where @option{-idirafter} would. 127 128@item -isysroot @var{dir} 129@opindex isysroot 130This option is like the @option{--sysroot} option, but applies only to 131header files (except for Darwin targets, where it applies to both header 132files and libraries). See the @option{--sysroot} option for more 133information. 134 135@item -imultilib @var{dir} 136@opindex imultilib 137Use @var{dir} as a subdirectory of the directory containing 138target-specific C++ headers. 139 140@item -nostdinc 141@opindex nostdinc 142Do not search the standard system directories for header files. 143Only the directories explicitly specified with @option{-I}, 144@option{-iquote}, @option{-isystem}, and/or @option{-idirafter} 145options (and the directory of the current file, if appropriate) 146are searched. 147 148@item -nostdinc++ 149@opindex nostdinc++ 150Do not search for header files in the C++-specific standard directories, 151but do still search the other standard directories. (This option is 152used when building the C++ library.) 153 154