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Options
for directory search
The following options specify
directories to search for header files, for libraries and for parts of
the compiler.
-
-Idir
Add the directory directory
to the head of the list of directories to be searched for header files.
This can be used to override a system header file, substituting your own
version, since these directories are searched before the system header
file directories. If you use more than one ‘-I’
option, the directories are scanned in left-to-right order; the standard
system directories come after.
-
-I-
Any directories you specify
with -I
options before the ‘-I-’
option are searched only for the case of #include
"file"; they are
not searched for #include
<file>. If
additional directories are specified with ‘-I’
options after the ‘-I-’,
these directories are searched for all #include
directives. (Ordinarily all ‘-I’
directories are used this way.) In addition, the ‘-I-’
option inhibits the use of the current directory (where the current input
file came from) as the first search directory for #include
"file". There
is no way to override this effect of ‘-I-’.
With ‘-I.’,
you can specify searching the directory which was current when the compiler
was invoked. That is not exactly the same as what the preprocessor does
by default, but it is often satisfactory.
‘-I-’
does not inhibit the use of the standard system directories for header
files. Thus, ‘-I-’
and ‘-nostdinc’
are independent.
-
-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/’
(see Specifying target
machine and compiler version).
For each subprogram to be
run, the compiler driver first tries, if any, the ‘-B’
prefix. If that name is not found, or if ‘-B’
was not specified, the driver tries two standard prefixes, which are /usr/lib/gcc/
and /usr/local/lib/gcc-lib/.
If neither of those results in a filename that is found, the unmodified
program name is searched for using the directories specified in your PATH
environment variable.
‘-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 includes files in the preprocessor,
because the compiler translates these options into -isystem
options for the pre-processor. In this case, the compiler appends include
to the prefix.
The run-time 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
discussedin the previous discussion 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 Environmental variables
affecting GNU CC.
-
-specs=file
Process file
after the
compiler reads in the standard ‘specs’
file, in order to override the defaults that the ‘gcc’
driver program uses when determining what switches to pass to ‘cc1’,
‘cc1plus’,
‘as’,
‘ld’,
etc. More than one -specs=file
can be specified on the command line, and they are processed in order,
from left to right.
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