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These options specify directories to search for header files, for libraries and for parts of the compiler:
-I dir-iquote dir-isystem dir-idirafter dir
Add the directory dir to the list of directories to be searched
for header files during preprocessing.
If dir begins with ‘=’ or $SYSROOT, then the ‘=’
or $SYSROOT is replaced by the sysroot prefix; see
--sysroot and -isysroot.
Directories specified with -iquote apply only to the quote
form of the directive, #include "file".
Directories specified with -I, -isystem,
or -idirafter apply to lookup for both the
#include "file" and
#include <file> directives.
You can specify any number or combination of these options on the command line to search for header files in several directories. The lookup order is as follows:
-iquote options are searched in left-to-right order,
as they appear on the command line.-I options are scanned in
left-to-right order.-isystem options are scanned in
left-to-right order.-idirafter options are scanned in
left-to-right order.You can use -I to override a system header
file, substituting your own version, since these directories are
searched before the standard system header file directories.
However, you should
not use this option to add directories that contain vendor-supplied
system header files; use -isystem for that.
The -isystem and -idirafter options also mark the directory
as a system directory, so that it gets the same special treatment that
is applied to the standard system directories.
If a standard system include directory, or a directory specified with
-isystem, is also specified with -I, the -I
option is ignored. The directory is still searched but as a
system directory at its normal position in the system include chain.
This is to ensure that GCC’s procedure to fix buggy system headers and
the ordering for the #include_next directive are not inadvertently
changed.
If you really need to change the search order for system directories,
use the -nostdinc and/or -isystem options.
-I-
Split the include path.
This option has been deprecated. Please use -iquote instead for
-I directories before the -I- and remove the -I-
option.
Any directories specified with -I
options before -I- are searched only for headers requested with
#include "file"; they are not searched for
#include <file>. If additional directories are
specified with -I options after the -I-, those
directories are searched for all ‘#include’ directives.
In addition, -I- inhibits the use of the directory of the current
file directory as the first search directory for #include "file". There is no way to override this effect of -I-.
-iprefix prefix
Specify prefix as the prefix for subsequent -iwithprefix
options. If the prefix represents a directory, you should include the
final ‘/’.
-iwithprefix dir-iwithprefixbefore dir
Append dir to the prefix specified previously with
-iprefix, and add the resulting directory to the include search
path. -iwithprefixbefore puts it in the same place -I
would; -iwithprefix puts it where -idirafter would.
-isysroot dir
This option is like the --sysroot option, but applies only to
header files (except for Darwin targets, where it applies to both header
files and libraries). See the --sysroot option for more
information.
-imultilib dir
Use dir as a subdirectory of the directory containing
target-specific C++ headers.
-nostdinc
Do not search the standard system directories for header files.
Only the directories explicitly specified with -I,
-iquote, -isystem, and/or -idirafter
options (and the directory of the current file, if appropriate)
are searched.
-nostdinc++
Do not search for header files in the C++-specific standard directories, but do still search the other standard directories. (This option is used when building the C++ library.)
-iplugindir=dir
Set the directory to search for plugins that are passed
by -fplugin=name instead of
-fplugin=path/name.so. This option is not meant
to be used by the user, but only passed by the driver.
-Ldir
Add directory dir to the list of directories to be searched
for -l.
-Bprefix
This option specifies where to find the executables, libraries, include files, and data files of the compiler itself.
The compiler driver program runs one or more of the subprograms
cpp, cc1, as and ld. It tries
prefix as a prefix for each program it tries to run, both with and
without ‘machine/version/’ for the corresponding target
machine and compiler version.
For each subprogram to be run, the compiler driver first tries the
-B prefix, if any. If that name is not found, or if -B
is not specified, the driver tries two standard prefixes,
/usr/lib/gcc/ and /usr/local/lib/gcc/. If neither of
those results in a file name that is found, the unmodified program
name is searched for using the directories specified in your
PATH environment variable.
The compiler checks to see if the path provided by -B
refers to a directory, and if necessary it adds a directory
separator character at the end of the path.
-B prefixes that effectively specify directory names also apply
to libraries in the linker, because the compiler translates these
options into -L options for the linker. They also apply to
include files in the preprocessor, because the compiler translates these
options into -isystem options for the preprocessor. In this case,
the compiler appends ‘include’ to the prefix.
The runtime support file libgcc.a can also be searched for using
the -B prefix, if needed. If it is not found there, the two
standard prefixes above are tried, and that is all. The file is left
out of the link if it is not found by those means.
Another way to specify a prefix much like the -B prefix is to use
the environment variable GCC_EXEC_PREFIX. See Environment Variables.
As a special kludge, if the path provided by -B is
[dir/]stageN/, where N is a number in the range 0 to
9, then it is replaced by [dir/]include. This is to help
with boot-strapping the compiler.
-no-canonical-prefixes
Do not expand any symbolic links, resolve references to ‘/../’
or ‘/./’, or make the path absolute when generating a relative
prefix.
--sysroot=dir
Use dir as the logical root directory for headers and libraries.
For example, if the compiler normally searches for headers in
/usr/include and libraries in /usr/lib, it instead
searches dir/usr/include and dir/usr/lib.
If you use both this option and the -isysroot option, then
the --sysroot option applies to libraries, but the
-isysroot option applies to header files.
The GNU linker (beginning with version 2.16) has the necessary support
for this option. If your linker does not support this option, the
header file aspect of --sysroot still works, but the
library aspect does not.
--no-sysroot-suffix
For some targets, a suffix is added to the root directory specified
with --sysroot, depending on the other options used, so that
headers may for example be found in
dir/suffix/usr/include instead of
dir/usr/include. This option disables the addition of
such a suffix.
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