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This chapter contains information that the libtool maintainer finds important. It will be of no use to you unless you are considering porting libtool to new systems, or writing your own libtool.
| 13.1 Porting libtool to new systems | How to port libtool to new systems. | |
| 13.2 Tested platforms | When libtool was last tested. | |
| 13.3 Platform quirks | Information about different library systems. | |
13.4 libtool script contents | Configuration information that libtool uses. | |
| 13.5 Cheap tricks | Making libtool maintainership easier. |
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Before you embark on porting libtool to an unsupported system, it is worthwhile to send e-mail to the libtool mailing list libtool@gnu.org, to make sure that you are not duplicating existing work.
If you find that any porting documentation is missing, please complain! Complaints with patches and improvements to the documentation, or to libtool itself, are more than welcome.
| 13.1.1 Information sources | Where to find relevant documentation | |
| 13.1.2 Porting inter-library dependencies support | Implementation details explained |
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Once it is clear that a new port is necessary, you'll generally need the following information:
You need the output of config.guess for this system, so that you
can make changes to the libtool configuration process without affecting
other systems.
ld and ccThese generally describe what flags are used to generate PIC, to create shared libraries, and to link against only static libraries. You may need to follow some cross references to find the information that is required.
ld.so, rtld, or equivalentThese are a valuable resource for understanding how shared libraries are loaded on the system.
ldconfig, or equivalentThis page usually describes how to install shared libraries.
This shows the naming convention for shared libraries on the system, including which names should be symbolic links.
Some systems have special documentation on how to build and install shared libraries.
If you know how to program the Bourne shell, then you can complete the port yourself; otherwise, you'll have to find somebody with the relevant skills who will do the work. People on the libtool mailing list are usually willing to volunteer to help you with new ports, so you can send the information to them.
To do the port yourself, you'll definitely need to modify the
libtool.m4 macros in order to make platform-specific changes to
the configuration process. You should search that file for the
PORTME keyword, which will give you some hints on what you'll
need to change. In general, all that is involved is modifying the
appropriate configuration variables (see section libtool script contents).
Your best bet is to find an already-supported system that is similar to
yours, and make your changes based on that. In some cases, however,
your system will differ significantly from every other supported system,
and it may be necessary to add new configuration variables, and modify
the ltmain.in script accordingly. Be sure to write to the
mailing list before you make changes to ltmain.in, since they may
have advice on the most effective way of accomplishing what you want.
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Since version 1.2c, libtool has re-introduced the ability to do inter-library dependency on some platforms, thanks to a patch by Toshio Kuratomi badger@prtr-13.ucsc.edu. Here's a shortened version of the message that contained his patch:
The basic architecture is this: in `libtool.m4', the person who writes libtool makes sure `$deplibs' is included in `$archive_cmds' somewhere and also sets the variable `$deplibs_check_method', and maybe `$file_magic_cmd' when `deplibs_check_method' is file_magic.
`deplibs_check_method' can be one of five things:
looks in the library link path for libraries that have the right libname. Then it runs `$file_magic_cmd' on the library and checks for a match against the extended regular expression regex. When file_magic_test_file is set by `libtool.m4', it is used as an argument to `$file_magic_cmd' in order to verify whether the regular expression matches its output, and warn the user otherwise.
just checks whether it is possible to link a program out of a list of
libraries, and checks which of those are listed in the output of
ldd. It is currently unused, and will probably be dropped in the
future.
will pass everything without any checking. This may work on platforms in which code is position-independent by default and inter-library dependencies are properly supported by the dynamic linker, for example, on DEC OSF/1 3 and 4.
It causes deplibs to be reassigned deplibs="". That way `archive_cmds' can contain deplibs on all platforms, but not have deplibs used unless needed.
is the default for all systems unless overridden in `libtool.m4'. It is the same as `none', but it documents that we really don't know what the correct value should be, and we welcome patches that improve it.
Then in `ltmain.in' we have the real workhorse: a little initialization and postprocessing (to setup/release variables for use with eval echo libname_spec etc.) and a case statement that decides which method is being used. This is the real code... I wish I could condense it a little more, but I don't think I can without function calls. I've mostly optimized it (moved things out of loops, etc) but there is probably some fat left. I thought I should stop while I was ahead, work on whatever bugs you discover, etc before thinking about more than obvious optimizations.
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This table describes when libtool was last known to be tested on platforms where it claims to support shared libraries:
------------------------------------------------------- canonical host name compiler libtool results (tools versions) release ------------------------------------------------------- alpha-dec-osf5.1 cc 1.3e ok (1.910) alpha-dec-osf4.0f gcc 1.3e ok (1.910) alpha-dec-osf4.0f cc 1.3e ok (1.910) alpha-dec-osf3.2 gcc 0.8 ok alpha-dec-osf3.2 cc 0.8 ok alpha-dec-osf2.1 gcc 1.2f NS alpha*-unknown-linux-gnu gcc 1.3b ok (egcs-1.1.2, GNU ld 2.9.1.0.23) hppa2.0w-hp-hpux11.00 cc 1.2f ok hppa2.0-hp-hpux10.20 cc 1.3.2 ok hppa1.1-hp-hpux10.20 gcc 1.2f ok hppa1.1-hp-hpux10.20 cc 1.3c ok (1.821) hppa1.1-hp-hpux10.10 gcc 1.2f ok hppa1.1-hp-hpux10.10 cc 1.2f ok hppa1.1-hp-hpux9.07 gcc 1.2f ok hppa1.1-hp-hpux9.07 cc 1.2f ok hppa1.1-hp-hpux9.05 gcc 1.2f ok hppa1.1-hp-hpux9.05 cc 1.2f ok hppa1.1-hp-hpux9.01 gcc 1.2f ok hppa1.1-hp-hpux9.01 cc 1.2f ok i*86-*-beos gcc 1.2f ok i*86-*-bsdi4.0.1 gcc 1.3c ok (gcc-2.7.2.1) i*86-*-bsdi4.0 gcc 1.2f ok i*86-*-bsdi3.1 gcc 1.2e NS i*86-*-bsdi3.0 gcc 1.2e NS i*86-*-bsdi2.1 gcc 1.2e NS i*86-pc-cygwin gcc 1.3b NS (egcs-1.1 stock b20.1 compiler) i*86-*-dguxR4.20MU01 gcc 1.2 ok i*86-*-freebsd4.3 gcc 1.3e ok (1.912) i*86-*-freebsdelf4.0 gcc 1.3c ok (egcs-1.1.2) i*86-*-freebsdelf3.2 gcc 1.3c ok (gcc-2.7.2.1) i*86-*-freebsdelf3.1 gcc 1.3c ok (gcc-2.7.2.1) i*86-*-freebsdelf3.0 gcc 1.3c ok i*86-*-freebsd3.0 gcc 1.2e ok i*86-*-freebsd2.2.8 gcc 1.3c ok (gcc-2.7.2.1) i*86-*-freebsd2.2.6 gcc 1.3b ok (egcs-1.1 & gcc-2.7.2.1, native ld) i*86-*-freebsd2.1.5 gcc 0.5 ok i*86-*-netbsd1.5 gcc 1.3e ok (1.901) (egcs-1.1.2) i*86-*-netbsd1.4 gcc 1.3c ok (egcs-1.1.1) i*86-*-netbsd1.4.3A gcc 1.3e ok (1.901) i*86-*-netbsd1.3.3 gcc 1.3c ok (gcc-2.7.2.2+myc2) i*86-*-netbsd1.3.2 gcc 1.2e ok i*86-*-netbsd1.3I gcc 1.2e ok (egcs 1.1?) i*86-*-netbsd1.2 gcc 0.9g ok i*86-*-linux-gnu gcc 1.3e ok (1.901) (Red Hat 7.0, gcc "2.96") i*86-*-linux-gnu gcc 1.3e ok (1.911) (SuSE 7.0, gcc 2.95.2) i*86-*-linux-gnulibc1 gcc 1.2f ok i*86-*-openbsd2.5 gcc 1.3c ok (gcc-2.8.1) i*86-*-openbsd2.4 gcc 1.3c ok (gcc-2.8.1) i*86-*-solaris2.7 gcc 1.3b ok (egcs-1.1.2, native ld) i*86-*-solaris2.6 gcc 1.2f ok i*86-*-solaris2.5.1 gcc 1.2f ok i*86-ncr-sysv4.3.03 gcc 1.2f ok i*86-ncr-sysv4.3.03 cc 1.2e ok (cc -Hnocopyr) i*86-pc-sco3.2v5.0.5 cc 1.3c ok i*86-pc-sco3.2v5.0.5 gcc 1.3c ok (gcc 95q4c) i*86-pc-sco3.2v5.0.5 gcc 1.3c ok (egcs-1.1.2) i*86-sco-sysv5uw7.1.1 gcc 1.3e ok (1.901) (gcc-2.95.2, SCO linker) i*86-UnixWare7.1.0-sysv5 cc 1.3c ok i*86-UnixWare7.1.0-sysv5 gcc 1.3c ok (egcs-1.1.1) m68k-next-nextstep3 gcc 1.2f NS m68k-sun-sunos4.1.1 gcc 1.2f NS (gcc-2.5.7) m88k-dg-dguxR4.12TMU01 gcc 1.2 ok m88k-motorola-sysv4 gcc 1.3 ok (egcs-1.1.2) mips-sgi-irix6.5 gcc 1.2f ok (gcc-2.8.1) mips-sgi-irix6.4 gcc 1.2f ok mips-sgi-irix6.3 gcc 1.3b ok (egcs-1.1.2, native ld) mips-sgi-irix6.3 cc 1.3b ok (cc 7.0) mips-sgi-irix6.2 gcc 1.2f ok mips-sgi-irix6.2 cc 0.9 ok mips-sgi-irix5.3 gcc 1.2f ok (egcs-1.1.1) mips-sgi-irix5.3 gcc 1.2f NS (gcc-2.6.3) mips-sgi-irix5.3 cc 0.8 ok mips-sgi-irix5.2 gcc 1.3b ok (egcs-1.1.2, native ld) mips-sgi-irix5.2 cc 1.3b ok (cc 3.18) mips-sni-sysv4 cc 1.3.5 ok (Siemens C-compiler) mips-sni-sysv4 gcc 1.3.5 ok (gcc-2.7.2.3, GNU assembler 2.8.1, native ld) mipsel-unknown-openbsd2.1 gcc 1.0 ok powerpc-apple-darwin6.4 gcc 1.5 ok (apple dev tools released 12/2002) powerpc-ibm-aix4.3.1.0 gcc 1.2f ok (egcs-1.1.1) powerpc-ibm-aix4.2.1.0 gcc 1.2f ok (egcs-1.1.1) powerpc-ibm-aix4.1.5.0 gcc 1.2f ok (egcs-1.1.1) powerpc-ibm-aix4.1.5.0 gcc 1.2f NS (gcc-2.8.1) powerpc-ibm-aix4.1.4.0 gcc 1.0 ok powerpc-ibm-aix4.1.4.0 xlc 1.0i ok rs6000-ibm-aix4.1.5.0 gcc 1.2f ok (gcc-2.7.2) rs6000-ibm-aix4.1.4.0 gcc 1.2f ok (gcc-2.7.2) rs6000-ibm-aix3.2.5 gcc 1.0i ok rs6000-ibm-aix3.2.5 xlc 1.0i ok sparc-sun-solaris2.8 gcc 1.3e ok (1.913) (gcc-2.95.3 & native ld) sparc-sun-solaris2.7 gcc 1.3e ok (1.913) (gcc-2.95.3 & native ld) sparc-sun-solaris2.6 gcc 1.3e ok (1.913) (gcc-2.95.3 & native ld) sparc-sun-solaris2.5.1 gcc 1.3e ok (1.911) sparc-sun-solaris2.5 gcc 1.3b ok (egcs-1.1.2, GNU ld 2.9.1 & native ld) sparc-sun-solaris2.5 cc 1.3b ok (SC 3.0.1) sparc-sun-solaris2.4 gcc 1.0a ok sparc-sun-solaris2.4 cc 1.0a ok sparc-sun-solaris2.3 gcc 1.2f ok sparc-sun-sunos4.1.4 gcc 1.2f ok sparc-sun-sunos4.1.4 cc 1.0f ok sparc-sun-sunos4.1.3_U1 gcc 1.2f ok sparc-sun-sunos4.1.3C gcc 1.2f ok sparc-sun-sunos4.1.3 gcc 1.3b ok (egcs-1.1.2, GNU ld 2.9.1 & native ld) sparc-sun-sunos4.1.3 cc 1.3b ok sparc-unknown-bsdi4.0 gcc 1.2c ok sparc-unknown-linux-gnulibc1 gcc 1.2f ok sparc-unknown-linux-gnu gcc 1.3b ok (egcs-1.1.2, GNU ld 2.9.1.0.23) sparc64-unknown-linux-gnu gcc 1.2f ok Notes: - "ok" means "all tests passed". - "NS" means "Not Shared", but OK for static libraries |
Note: The vendor-distributed HP-UX sed(1) programs are horribly
broken, and cannot handle libtool's requirements, so users may report
unusual problems. There is no workaround except to install a working
sed (such as GNU sed) on these systems.
Note: The vendor-distributed NCR MP-RAS cc programs emits
copyright on standard error that confuse tests on size of
`conftest.err'. The workaround is to specify CC
when run configure with CC='cc -Hnocopyr'.
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This section is dedicated to the sanity of the libtool maintainers. It describes the programs that libtool uses, how they vary from system to system, and how to test for them.
Because libtool is a shell script, it can be difficult to understand just by reading it from top to bottom. This section helps show why libtool does things a certain way. Combined with the scripts themselves, you should have a better sense of how to improve libtool, or write your own.
| 13.3.1 References | Finding more information. | |
| 13.3.2 Compilers | Creating object files from source files. | |
| 13.3.3 Reloadable objects | Binding object files together. | |
| 13.3.4 Multiple dependencies | Removing duplicate dependent libraries. | |
| 13.3.5 Archivers | Programs that create static archives. |
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The following is a list of valuable documentation references:
SGI's IRIX Manual Pages, which can be found at http://techpubs.sgi.com/cgi-bin/infosrch.cgi?cmd=browse&db=man.
Sun's free service area (http://www.sun.com/service/online/free.html) and documentation server (http://docs.sun.com/).
Compaq's Tru64 UNIX online documentation is at
(http://tru64unix.compaq.com/faqs/publications/pub_page/doc_list.html)
with C++ documentation at
(http://tru64unix.compaq.com/cplus/docs/index.htm).
Hewlett-Packard has online documentation at (http://docs.hp.com/index.html).
IBM has online documentation at (http://www.rs6000.ibm.com/resource/aix_resource/Pubs/).
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The only compiler characteristics that affect libtool are the flags needed (if any) to generate PIC objects. In general, if a C compiler supports certain PIC flags, then any derivative compilers support the same flags. Until there are some noteworthy exceptions to this rule, this section will document only C compilers.
The following C compilers have standard command line options, regardless of the platform:
gccThis is the GNU C compiler, which is also the system compiler for many free operating systems (FreeBSD, GNU/Hurd, GNU/Linux, Lites, NetBSD, and OpenBSD, to name a few).
The `-fpic' or `-fPIC' flags can be used to generate position-independent code. `-fPIC' is guaranteed to generate working code, but the code is slower on m68k, m88k, and Sparc chips. However, using `-fpic' on those chips imposes arbitrary size limits on the shared libraries.
The rest of this subsection lists compilers by the operating system that they are bundled with:
aix3* aix4*Most AIX compilers have no PIC flags, since AIX (with the exception of AIX for IA-64) runs on PowerPC and RS/6000 chips. (11)
hpux10*Use `+Z' to generate PIC.
osf3*Digital/UNIX 3.x does not have PIC flags, at least not on the PowerPC platform.
solaris2*Use `-KPIC' to generate PIC.
sunos4*Use `-PIC' to generate PIC.
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On all known systems, a reloadable object can be created by running ld -r -o output.o input1.o input2.o. This reloadable object may be treated as exactly equivalent to other objects.
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On most modern platforms the order that dependent libraries are listed has no effect on object generation. In theory, there are platforms which require libraries which provide missing symbols to other libraries to listed after those libraries whose symbols they provide.
Particularly, if a pair of static archives each resolve some of the other's symbols, it might be necessary to list one of those archives both before and after the other one. Libtool does not currently cope with this situation well, since duplicate libraries are removed from the link line by default. Libtool provides the command line option `--preserve-dup-deps' to preserve all duplicate dependencies in cases where it is necessary.
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On all known systems, building a static library can be accomplished by running ar cru libname.a obj1.o obj2.o …, where the `.a' file is the output library, and each `.o' file is an object file.
On all known systems, if there is a program named ranlib, then it
must be used to "bless" the created library before linking against it,
with the ranlib libname.a command. Some systems, like Irix,
use the ar ts command, instead.
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libtool script contents Since version 1.4, the libtool script is generated by
configure (see section Configuring libtool). In earlier versions,
configure achieved this by calling a helper script called
`ltconfig'. From libtool version 0.7 to 1.0, this script
simply set shell variables, then sourced the libtool backend,
ltmain.sh. ltconfig from libtool version 1.1 through 1.3
inlined the contents of ltmain.sh into the generated
libtool, which improved performance on many systems. The tests
that `ltconfig' used to perform are now kept in `libtool.m4'
where thay can be written using Autoconf. This has the runtime
performance benefits of inlined ltmain.sh, and improves
the build time a little while considerably easing the amount of raw
shell code that used to need maintaining.
The convention used for naming variables which hold shell commands for
delayed evaluation, is to use the suffix _cmd where a single
line of valid shell script is needed, and the suffix _cmds where
multiple lines of shell script may be delayed for later
evaluation. By convention, _cmds variables delimit the
evaluation units with the ~ character where necessary.
Here is a listing of each of the configuration variables, and how they
are used within ltmain.sh (see section Configuring libtool):
The name of the system library archiver.
The name of the C compiler used to configure libtool.
The name of the linker that libtool should use internally for reloadable linking and possibly shared libraries.
The name of a BSD-compatible nm program, which produces listings
of global symbols in one the following formats:
address C global-variable-name address D global-variable-name address T global-function-name |
Set to the name of the ranlib program, if any.
The flag that is used by `archive_cmds' in order to declare that there will be unresolved symbols in the resulting shared library. Empty, if no such flag is required. Set to `unsupported' if there is no way to generate a shared library with references to symbols that aren't defined in that library.
Whether libtool should automatically generate a list of exported symbols using export_symbols_cmds before linking an archive. Set to `yes' or `no'. Default is `no'.
Commands used to create shared libraries, shared libraries with `-export-symbols' and static libraries, respectively.
If the shared library depends on a static library, `old_archive_from_new_cmds' contains the commands used to create that static library. If this variable is not empty, `old_archive_cmds' is not used.
If a static library must be created from the export symbol list in order to correctly link with a shared library, `old_archive_from_expsyms_cmds' contains the commands needed to create that static library. When these commands are executed, the variable soname contains the name of the shared library in question, and the $objdir/$newlib contains the path of the static library these commands should build. After executing these commands, libtool will proceed to link against $objdir/$newlib instead of soname.
Whether libtool should build shared libraries on this system. Set to `yes' or `no'.
Whether libtool should build static libraries on this system. Set to `yes' or `no'.
Whether the compiler supports the -c and -o options
simultaneously. Set to `yes' or `no'.
Whether the compiler supports compiling directly to a ".lo" file, i.e whether object files do not have to have the suffix ".o". Set to `yes' or `no'.
Whether dlopen is supported on the platform.
Set to `yes' or `no'.
Whether it is possible to dlopen the executable itself.
Set to `yes' or `no'.
Whether it is possible to dlopen the executable itself, when it
is linked statically (`-all-static'). Set to `yes' or
`no'.
An echo program which does not interpret backslashes as an
escape character.
List of symbols that should not be listed in the preloaded symbols.
Compiler link flag that allows a dlopened shared library to reference symbols that are defined in the program.
Commands to extract exported symbols from libobjs to the file export_symbols.
Commands to extract the exported symbols list from a shared library. These commands are executed if there is no file $objdir/$soname-def, and should write the names of the exported symbols to that file, for the use of `old_archive_from_expsyms_cmds'.
Determines whether libtool will privilege the installer or the developer. The assumption is that installers will seldom run programs in the build tree, and the developer will seldom install. This is only meaningful on platforms in which shlibpath_overrides_runpath is not `yes', so fast_install will be set to `needless' in this case. If fast_install set to `yes', libtool will create programs that search for installed libraries, and, if a program is run in the build tree, a new copy will be linked on-demand to use the yet-to-be-installed libraries. If set to `no', libtool will create programs that use the yet-to-be-installed libraries, and will link a new copy of the program at install time. The default value is `yes' or `needless', depending on platform and configuration flags, and it can be turned from `yes' to `no' with the configure flag `--disable-fast-install'.
Commands to tell the dynamic linker how to find shared libraries in a specific directory.
Same as finish_cmds, except the commands are not displayed.
Expression to fix the shell variable $srcfile for the compiler.
A pipeline that takes the output of NM, and produces a listing of raw symbols followed by their C names. For example:
$ eval "$NM progname | $global_symbol_pipe" D symbol1 C-symbol1 T symbol2 C-symbol2 C symbol3 C-symbol3 … $ |
The first column contains the symbol type (used to tell data from code on some platforms), but its meaning is system dependent.
A pipeline that translates the output of global_symbol_pipe into proper C declarations. On platforms whose linkers differentiate code from data, such as HP/UX, data symbols will be declared as such, and code symbols will be declared as functions. On platforms that don't care, everything is assumed to be data.
Either `immediate' or `relink', depending on whether shared library paths can be hardcoded into executables before they are installed, or if they need to be relinked.
Set to `yes' or `no', depending on whether the linker hardcodes directories if a library is directly specified on the command line (such as `dir/libname.a') when hardcode_libdir_flag_spec is specified.
Whether the platform supports hardcoding of run-paths into libraries. If enabled, linking of programs will be much simpler but libraries will need to be relinked during installation. Set to `yes' or `no'.
Flag to hardcode a libdir variable into a binary, so that the dynamic linker searches libdir for shared libraries at runtime. If it is empty, libtool will try to use some other hardcoding mechanism.
If the compiler only accepts a single hardcode_libdir_flag, then this variable contains the string that should separate multiple arguments to that flag.
Set to `yes' or `no', depending on whether the linker hardcodes directories specified by `-L' flags into the resulting executable when hardcode_libdir_flag_spec is specified.
Set to `yes' or `no', depending on whether the linker hardcodes directories by writing the contents of `$shlibpath_var' into the resulting executable when hardcode_libdir_flag_spec is specified. Set to `unsupported' if directories specified by `$shlibpath_var' are searched at run time, but not at link time.
For information purposes, set to the specified and canonical names of the system that libtool was configured for.
List of symbols that must always be exported when using export_symbols.
The standard old archive suffix (normally "a").
The format of a library name prefix. On all Unix systems, static libraries are called `libname.a', but on some systems (such as OS/2 or MS-DOS), the library is just called `name.a'.
A list of shared library names. The first is the name of the file, the rest are symbolic links to the file. The name in the list is the file name that the linker finds when given `-lname'.
Whether libtool must link a program against all its dependency libraries. Set to `yes' or `no'. Default is `unknown', which is a synonym for `yes'.
Linker flag (passed through the C compiler) used to prevent dynamic linking.
Whether libtool should automatically prefix module names with 'lib'.
Set to `yes' or `no'. By default, it is `unknown', which
means the same as `yes', but documents that we are not really sure
about it.
`yes' means that it is possible both to dlopen and to
link against a library without 'lib' prefix,
i.e. it requires hardcode_direct to be `yes'.
Whether versioning is required for libraries, i.e. whether the dynamic linker requires a version suffix for all libraries. Set to `yes' or `no'. By default, it is `unknown', which means the same as `yes', but documents that we are not really sure about it.
Whether files must be locked to prevent conflicts when compiling simultaneously. Set to `yes' or `no'.
Compiler flag to disable builtin functions that conflict with declaring
external global symbols as char.
The flag that is used by `archive_cmds' in order to declare that there will be no unresolved symbols in the resulting shared library. Empty, if no such flag is required.
The name of the directory that contains temporary libtool files.
The standard object file suffix (normally "o").
Any additional compiler flags for building library object files.
Commands run after installing a shared or static library, respectively.
Commands run after uninstalling a shared or static library, respectively.
Commands to create a reloadable object.
The environment variable that tells the linker which directories to hardcode in the resulting executable.
Indicates whether it is possible to override the hard-coded library
search path of a program with an environment variable. If this is set
to no, libtool may have to create two copies of a program in the build
tree, one to be installed and one to be run in the build tree only.
When each of these copies is created depends on the value of
fast_install. The default value is `unknown', which is
equivalent to `no'.
The environment variable that tells the dynamic linker where to find shared libraries.
The name coded into shared libraries, if different from the real name of the file.
Command to strip a shared (striplib) or static (old_striplib)
library, respectively. If these variables are empty, the strip flag
in the install mode will be ignored for libraries (see section Install mode).
Expression to get the run-time system library search path. Directories that appear in this list are never hard-coded into executables.
Expression to get the compile-time system library search path. This
variable is used by libtool when it has to test whether a certain
library is shared or static. The directories listed in
shlibpath_var are automatically appended to this list, every time
libtool runs (i.e., not at configuration time), because some linkers use
this variable to extend the library search path. Linker switches such
as -L also augment the search path.
Linker flag (passed through the C compiler) used to generate thread-safe libraries.
The library version numbering type. One of `libtool', `freebsd-aout', `freebsd-elf', `irix', `linux', `osf', `sunos', `windows', or `none'.
Compiler flag to generate shared objects from convenience archives.
The C compiler flag that allows libtool to pass a flag directly to the
linker. Used as: ${wl}some-flag.
Variables ending in `_cmds' or `_eval' contain a
`~'-separated list of commands that are evaled one after
another. If any of the commands return a nonzero exit status, libtool
generally exits with an error message.
Variables ending in `_spec' are evaled before being used by
libtool.
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Here are a few tricks that you can use in order to make maintainership easier:
When people report bugs, ask them to use the `--config', `--debug', or `--features' flags, if you think they will help you. These flags are there to help you get information directly, rather than having to trust second-hand observation.
Rather than reconfiguring libtool every time I make a change to
ltmain.in, I keep a permanent libtool script in my
PATH, which sources ltmain.in directly.
The following steps describe how to create such a script, where
/home/src/libtool is the directory containing the libtool source
tree, /home/src/libtool/libtool is a libtool script that has been
configured for your platform, and ~/bin is a directory in your
PATH:
trick$ cd ~/bin trick$ sed '/^# ltmain\.sh/q' /home/src/libtool/libtool > libtool trick$ echo '. /home/src/libtool/ltmain.in' >> libtool trick$ chmod +x libtool trick$ libtool --version ltmain.sh (GNU @PACKAGE@) @VERSION@@TIMESTAMP@ trick$ |
The output of the final `libtool --version' command shows that the
ltmain.in script is being used directly. Now, modify
~/bin/libtool or /home/src/libtool/ltmain.in directly in
order to test new changes without having to rerun configure.
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