1@c Copyright (C) 1999-2020 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{=} or @code{$SYSROOT}, then the @samp{=} 26or @code{$SYSROOT} is replaced by the sysroot prefix; see 27@option{--sysroot} and @option{-isysroot}. 28 29Directories specified with @option{-iquote} apply only to the quote 30form of the directive, @code{@w{#include "@var{file}"}}. 31Directories specified with @option{-I}, @option{-isystem}, 32or @option{-idirafter} apply to lookup for both the 33@code{@w{#include "@var{file}"}} and 34@code{@w{#include <@var{file}>}} directives. 35 36You can specify any number or combination of these options on the 37command line to search for header files in several directories. 38The lookup order is as follows: 39 40@enumerate 41@item 42For the quote form of the include directive, the directory of the current 43file is searched first. 44 45@item 46For the quote form of the include directive, the directories specified 47by @option{-iquote} options are searched in left-to-right order, 48as they appear on the command line. 49 50@item 51Directories specified with @option{-I} options are scanned in 52left-to-right order. 53 54@item 55Directories specified with @option{-isystem} options are scanned in 56left-to-right order. 57 58@item 59Standard system directories are scanned. 60 61@item 62Directories specified with @option{-idirafter} options are scanned in 63left-to-right order. 64@end enumerate 65 66You can use @option{-I} to override a system header 67file, substituting your own version, since these directories are 68searched before the standard system header file directories. 69However, you should 70not use this option to add directories that contain vendor-supplied 71system header files; use @option{-isystem} for that. 72 73The @option{-isystem} and @option{-idirafter} options also mark the directory 74as a system directory, so that it gets the same special treatment that 75is applied to the standard system directories. 76@ifset cppmanual 77@xref{System Headers}. 78@end ifset 79 80If a standard system include directory, or a directory specified with 81@option{-isystem}, is also specified with @option{-I}, the @option{-I} 82option is ignored. The directory is still searched but as a 83system directory at its normal position in the system include chain. 84This is to ensure that GCC's procedure to fix buggy system headers and 85the ordering for the @code{#include_next} directive are not inadvertently 86changed. 87If you really need to change the search order for system directories, 88use the @option{-nostdinc} and/or @option{-isystem} options. 89@ifset cppmanual 90@xref{System Headers}. 91@end ifset 92 93@item -I- 94@opindex I- 95Split the include path. 96This option has been deprecated. Please use @option{-iquote} instead for 97@option{-I} directories before the @option{-I-} and remove the @option{-I-} 98option. 99 100Any directories specified with @option{-I} 101options before @option{-I-} are searched only for headers requested with 102@code{@w{#include "@var{file}"}}; they are not searched for 103@code{@w{#include <@var{file}>}}. If additional directories are 104specified with @option{-I} options after the @option{-I-}, those 105directories are searched for all @samp{#include} directives. 106 107In addition, @option{-I-} inhibits the use of the directory of the current 108file directory as the first search directory for @code{@w{#include 109"@var{file}"}}. There is no way to override this effect of @option{-I-}. 110@ifset cppmanual 111@xref{Search Path}. 112@end ifset 113 114@item -iprefix @var{prefix} 115@opindex iprefix 116Specify @var{prefix} as the prefix for subsequent @option{-iwithprefix} 117options. If the prefix represents a directory, you should include the 118final @samp{/}. 119 120@item -iwithprefix @var{dir} 121@itemx -iwithprefixbefore @var{dir} 122@opindex iwithprefix 123@opindex iwithprefixbefore 124Append @var{dir} to the prefix specified previously with 125@option{-iprefix}, and add the resulting directory to the include search 126path. @option{-iwithprefixbefore} puts it in the same place @option{-I} 127would; @option{-iwithprefix} puts it where @option{-idirafter} would. 128 129@item -isysroot @var{dir} 130@opindex isysroot 131This option is like the @option{--sysroot} option, but applies only to 132header files (except for Darwin targets, where it applies to both header 133files and libraries). See the @option{--sysroot} option for more 134information. 135 136@item -imultilib @var{dir} 137@opindex imultilib 138Use @var{dir} as a subdirectory of the directory containing 139target-specific C++ headers. 140 141@item -nostdinc 142@opindex nostdinc 143Do not search the standard system directories for header files. 144Only the directories explicitly specified with @option{-I}, 145@option{-iquote}, @option{-isystem}, and/or @option{-idirafter} 146options (and the directory of the current file, if appropriate) 147are searched. 148 149@item -nostdinc++ 150@opindex nostdinc++ 151Do not search for header files in the C++-specific standard directories, 152but do still search the other standard directories. (This option is 153used when building the C++ library.) 154 155