Using and Porting the GNU Compiler Collection (GCC)
These options come into play when the compiler links object files into an executable output file. They are meaningless if the compiler is not doing a link step.
object-file-name
-c
-S
-E
-llibrary
It makes a difference where in the command you write this option; the
linker searches processes libraries and object files in the order they
are specified. Thus, `foo.o -lz bar.o
' searches library `z
'
after file `foo.o
' but before `bar.o
'. If `bar.o
' refers
to functions in `z
', those functions may not be loaded.
The linker searches a standard list of directories for the library,
which is actually a file named `liblibrary.a
'. The linker
then uses this file as if it had been specified precisely by name.
The directories searched include several standard system directories
plus any that you specify with `-L
'.
Normally the files found this way are library files---archive files
whose members are object files. The linker handles an archive file by
scanning through it for members which define symbols that have so far
been referenced but not defined. But if the file that is found is an
ordinary object file, it is linked in the usual fashion. The only
difference between using an `-l
' option and specifying a file name
is that `-l
' surrounds library with `lib
' and `.a
'
and searches several directories.
-lobjc
-l
' option in order to
link an Objective C program.
-nostartfiles
-nostdlib
or -nodefaultlibs
is used.
-nodefaultlibs
-nostartfiles
is used. The compiler may generate calls to memcmp, memset, and memcpy
for System V (and ANSI C) environments or to bcopy and bzero for
BSD environments. These entries are usually resolved by entries in
libc. These entry points should be supplied through some other
mechanism when this option is specified.
-nostdlib
One of the standard libraries bypassed by `-nostdlib
' and
`-nodefaultlibs
' is `libgcc.a
', a library of internal subroutines
that GCC uses to overcome shortcomings of particular machines, or special
needs for some languages.
(See Interface, for more discussion of
`libgcc.a
'.)
In most cases, you need `libgcc.a
' even when you want to avoid
other standard libraries. In other words, when you specify `-nostdlib
'
or `-nodefaultlibs
' you should usually specify `-lgcc
' as well.
This ensures that you have no unresolved references to internal GCC
library subroutines. (For example, `__main
', used to ensure C++
constructors will be called; see Collect2.)
-s
-static
-shared
-fpic
' or `-fPIC
' on some systems when
you specify this option.
-symbolic
-Xlinker -z -Xlinker defs
'). Only a few systems support
this option.
-Xlinker option
If you want to pass an option that takes an argument, you must use
`-Xlinker
' twice, once for the option and once for the argument.
For example, to pass `-assert definitions
', you must write
`-Xlinker -assert -Xlinker definitions
'. It does not work to write
`-Xlinker "-assert definitions"
', because this passes the entire
string as a single argument, which is not what the linker expects.
-Wl,option
-u symbol
-u
' multiple times with
different symbols to force loading of additional library modules.
Using and Porting the GNU Compiler Collection (GCC)
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Context copyright by each document's author. See Free Software Foundation for information.