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These 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 section Specifying 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'
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 file name 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 preprocessor. 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 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 section Environment Variables Affecting GNU CC.
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