GNU Libtool

https://www.gnu.org/software/libtool/manual/html_node/
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### Install executable with libtool --mode=install (Ultrix example)

Source: https://www.gnu.org/software/libtool/manual/html_node/Installing-executables.html

Use this command to install an executable linked against uninstalled libtool libraries. The output shows the actual install command executed by libtool.

```shell
a23# libtool --mode=install install -c hell /usr/local/bin/hell
install -c hell /usr/local/bin/hell
a23#
```

--------------------------------

### Manual installation of static library with cp

Source: https://www.gnu.org/software/libtool/manual/html_node/Installing-libraries.html

Shows the traditional way to install a static library on a non-libtool system: copy the library into place and then run ranlib. The footnote warns not to strip static libraries or they will be unusable.

```shell
burger$ `su`
Password: `********`
burger# `cp libhello.a /usr/local/lib/libhello.a`
burger#

```

```shell
burger# `ranlib /usr/local/lib/libhello.a`
burger#

```

--------------------------------

### Install static library with libtool install mode using cp

Source: https://www.gnu.org/software/libtool/manual/html_node/Installing-libraries.html

Uses libtool's install mode with the cp command to install a static library. The output shows the actual commands executed, including copying the library and running ranlib.

```shell
a23# `libtool --mode=install cp libhello.la /usr/local/lib/libhello.la`
cp libhello.la /usr/local/lib/libhello.la
cp .libs/libhello.a /usr/local/lib/libhello.a
ranlib /usr/local/lib/libhello.a
a23#

```

--------------------------------

### Libtool linking against installed library

Source: https://www.gnu.org/software/libtool/manual/html_node/Linking-executables.html

Demonstrates using libtool to link against an installed library, showing how it adds the run-time path flag and dependencies automatically.

```shell
burger$ `libtool --mode=link gcc -g -O -o test test.o \
                /usr/local/lib/libhello.la`
gcc -g -O -o .libs/test test.o -Wl,--rpath \
        -Wl,/usr/local/lib /usr/local/lib/libhello.a -lm
creating test
burger$

```

--------------------------------

### Install shared library with libtool install mode using install -c

Source: https://www.gnu.org/software/libtool/manual/html_node/Installing-libraries.html

Uses libtool's install mode with the install -c command to install a shared library. The output shows the installation of the shared object, the libtool library, and the static library, followed by ranlib.

```shell
burger# `libtool --mode=install install -c libhello.la \
                /usr/local/lib/libhello.la`
install -c .libs/libhello.so.0.0 /usr/local/lib/libhello.so.0.0
install -c libhello.la /usr/local/lib/libhello.la
install -c .libs/libhello.a /usr/local/lib/libhello.a
ranlib /usr/local/lib/libhello.a
burger#

```

--------------------------------

### Build previous and current release candidates

Source: https://www.gnu.org/software/libtool/manual/html_node/Guided-version-info-update.html

Build and install the previous release and the current release candidate into separate directories before running the wizard.

```bash
$ rm -rf /tmp/prev /tmp/curr
$ tar xfz libfoo-1.4.tar.gz
$ (cd libfoo-1.4
   && ./configure --prefix=/tmp/prev
   && make
   && make install)
$ tar xfz libfoo-1.4.99.tar.gz
$ (cd libfoo-1.4.99
   && ./configure --prefix=/tmp/curr
   && make
   && make install)
```

--------------------------------

### Get post-installation hints with libtool finish mode

Source: https://www.gnu.org/software/libtool/manual/html_node/Installing-libraries.html

Runs libtool -n finish to display hints on what to do after installing libraries, such as setting LD_LIBRARY_PATH or using the -L flag during linking. The -n flag performs a dry run.

```shell
burger# `libtool -n finish /usr/local/lib`
PATH="$PATH:/sbin" ldconfig -m /usr/local/lib
-----------------------------------------------------------------
Libraries have been installed in:
   /usr/local/lib

To link against installed libraries in a given directory, LIBDIR,
you must use the '-LLIBDIR' flag during linking.

 You will also need to do one of the following:
   - add LIBDIR to the 'LD_LIBRARY_PATH' environment variable
     during execution
   - add LIBDIR to the 'LD_RUN_PATH' environment variable
     during linking
   - use the '-RLIBDIR' linker flag

See any operating system documentation about shared libraries for
more information, such as the ld and ld.so manual pages.
-----------------------------------------------------------------
burger#

```

--------------------------------

### Manual linking against installed library

Source: https://www.gnu.org/software/libtool/manual/html_node/Linking-executables.html

Shows the manual way to link against an already-installed library using gcc with -L and -l flags.

```shell
burger$ `gcc -g -O -o test test.o -L/usr/local/lib -lhello -lm`

```

--------------------------------

### Install executable with libtool --mode=install (wrapper script system)

Source: https://www.gnu.org/software/libtool/manual/html_node/Installing-executables.html

On shared library systems that require wrapper scripts, libtool ignores the wrapper script and installs the correct binary from .libs. The output shows the install command targeting .libs/hell.

```shell
burger# libtool --mode=install install -c hell /usr/local/bin/hell
install -c .libs/hell /usr/local/bin/hell
burger#
```

--------------------------------

### configure.ac: Embed installable libltdl with LTDL_INIT

Source: https://www.gnu.org/software/libtool/manual/html_node/Distributing-libltdl.html

Shows the configure.ac fragment to embed an installable libltdl. It sets the subdirectory with LT_CONFIG_LTDL_DIR, enables dlopen support with LT_INIT([dlopen]), and enables the installable library with LTDL_INIT([installable]). Replace 'installable' with 'convenience' for the convenience variant.

```autoconf
...
# Name the subdirectory that contains libltdl sources
LT_CONFIG_LTDL_DIR([libltdl])

# Configure libtool with dlopen support if possible
LT_INIT([dlopen])

# Enable building of the installable libltdl library
LTDL_INIT([installable])
...
```

--------------------------------

### Configure command with --enable-shared=bfd,gdb

Source: https://www.gnu.org/software/libtool/manual/html_node/LT_005fINIT.html

Example of running configure with --enable-shared=bfd,gdb to build shared libraries for the packages 'bfd' and 'gdb' but not for others like 'libg++'.

```shell
trick$ ./configure --enable-shared=bfd,gdb

```

--------------------------------

### foo.lo on static-only system

Source: https://www.gnu.org/software/libtool/manual/html_node/Creating-object-files.html

Example .lo file generated by libtool on a system that only supports static libraries. The pic_object is set to 'none'.

```text
# foo.lo - a libtool object file
# Generated by ltmain.sh (GNU libtool) 2.6.2
#
# Please DO NOT delete this file!
# It is necessary for linking the library.

# Name of the PIC object.
pic_object=none

# Name of the non-PIC object.
non_pic_object='foo.o'

```

--------------------------------

### Intrinsics module Makefile.am configuration

Source: https://www.gnu.org/software/libtool/manual/html_node/Linking-with-dlopened-modules.html

Example configuration for a module in a sibling directory, including a rule to build the required interface library.

```Makefile
AM_CPPFLAGS             = -I$(srcdir)/../libloader
AM_LDFLAGS              = -no-undefined -module -avoid-version \
                          -export-dynamic

noinst_LTLIBRARIES      = intrinsics.la

intrinsics_la_LIBADD    = ../libloader/libinterface.la

../libloader/libinterface.la:
        cd ../libloader && $(MAKE) $(AM_MAKEFLAGS) libinterface.la
```

--------------------------------

### Extract demo files from Autotest

Source: https://www.gnu.org/software/libtool/manual/html_node/Using-libtool.html

Run the demo test with specific flags to preserve artifacts, then copy the test directory to a demo folder. This provides the source files for the examples in this chapter.

```shell
burger$ make check TESTSUITEFLAGS="-d -k 'preloaded static library'"
burger$ cp -r tests/testsuite.dir/027 demo/

```

--------------------------------

### libtool --reorder-cache examples (second set)

Source: https://www.gnu.org/software/libtool/manual/html_node/Invoking-libtool.html

Shows the effect of --reorder-cache when the previously preferred directory is removed: the reordered list omits the removed directory and appends the remaining original directories.

```shell
$ `libtool --reorder-cache=/tmp/testing`
Original: /usr/lib /usr/X11R6/lib /usr/local/lib
Reordered: /tmp/testing /usr/lib /usr/X11R6/lib /usr/local/lib
$ `rm -rf /tmp/testing`
$ `libtool --reorder-cache=/usr/lib:/usr/X11R6/lib:/usr/local/lib`
Original: /tmp/testing /usr/lib /usr/X11R6/lib /usr/local/lib
Reordered: /usr/lib /usr/X11R6/lib /usr/local/lib

```

--------------------------------

### Iterating over module handles with lt_dlhandle_iterate

Source: https://www.gnu.org/software/libtool/manual/html_node/User-defined-module-data.html

Example loop that iterates over all module handles matching the given interface, starting with a NULL handle and continuing until lt_dlhandle_iterate returns NULL.

```c
lt_dlhandle handle = 0;
lt_dlinterface_id iface = my_interface_id;

while ((handle = lt_dlhandle_iterate (iface, handle)))
  {
    ...
  }

```

--------------------------------

### my_dlopenext: emulate lt_dlopenext using lt_dlopenadvise

Source: https://www.gnu.org/software/libtool/manual/html_node/Libltdl-interface.html

Shows how to initialize an lt_dladvise, set the ext hint, and call lt_dlopenadvise to emulate lt_dlopenext. The advise object is destroyed after use. On failure, lt_dladvise_init or lt_dladvise_ext returns non-zero and sets an error retrievable with lt_dlerror.

```c
lt_dlhandle
my_dlopenext (const char *filename)
{
  lt_dlhandle handle = 0;
  lt_dladvise advise;

  if (!lt_dladvise_init (&advise) && !lt_dladvise_ext (&advise))
    handle = lt_dlopenadvise (filename, advise);

  lt_dladvise_destroy (&advise);

  return handle;
}

```

--------------------------------

### Compile foo.c and hello.c with gcc

Source: https://www.gnu.org/software/libtool/manual/html_node/Creating-object-files.html

Creating object files for static library sources foo.c and hello.c.

```shell
burger$ `gcc -I. -g -O -c foo.c`
burger$ `gcc -I. -g -O -c hello.c`
burger$

```

--------------------------------

### Using macros in foo.h

Source: https://www.gnu.org/software/libtool/manual/html_node/C-header-files.html

Shows how to use the BEGIN_C_DECLS, END_C_DECLS, and PARAMS macros in a header file, with an include guard and a placeholder for the macro definitions.

```C
#ifndef FOO_H
#define FOO_H

/* The above macro definitions. */
#include "..."

BEGIN_C_DECLS

int foo PARAMS((void));
int hello PARAMS((void));

END_C_DECLS

#endif /* !FOO_H */

```

--------------------------------

### lt_dlinit

Source: https://www.gnu.org/software/libtool/manual/html_node/Libltdl-interface.html

Initializes libltdl. Must be called before using libltdl and may be called several times. Returns 0 on success, otherwise the number of errors.

```APIDOC
## lt_dlinit

### Description
Initialize libltdl. This function must be called before using libltdl and may be called several times. Return 0 on success, otherwise the number of errors.

### Function Signature
`int lt_dlinit (void)`

### Parameters
None.

### Return Value
- **int** - 0 on success, otherwise the number of errors.

```

--------------------------------

### configure.ac: Check for installed libltdl version using AC_CHECK_LIB

Source: https://www.gnu.org/software/libtool/manual/html_node/Distributing-libltdl.html

Use this configure.ac snippet after LTDL_INIT to verify that an installed libltdl is recent enough, by checking for the lt_dladvise_init symbol. It sets CFLAGS and LDFLAGS to include the libltdl headers and library, and aborts with an error if the installed libltdl is too old.

```autoconf
LT_INIT([dlopen])
LTDL_INIT

# The lt_dladvise_init symbol was added with libtool-2.2
if test yes != "$with_included_ltdl"; then
  save_CFLAGS=$CFLAGS
  save_LDFLAGS=$LDFLAGS
  CFLAGS="$CFLAGS $LTDLINCL"
  LDFLAGS="$LDFLAGS $LIBLTDL"
  AC_CHECK_LIB([ltdl], [lt_dladvise_init],
                [],
        [AC_MSG_ERROR([installed libltdl is too old])])
  LDFLAGS=$save_LDFLAGS
  CFLAGS=$save_CFLAGS
fi
```

--------------------------------

### Passing options to libtoolize via LIBTOOLIZE_OPTIONS

Source: https://www.gnu.org/software/libtool/manual/html_node/Invoking-libtoolize.html

Example of using the LIBTOOLIZE_OPTIONS environment variable with autoreconf to pass options to libtoolize.

```shell
trick$ `LIBTOOLIZE_OPTIONS=--no-warn,--quiet autoreconf --install`

```

--------------------------------

### Set up Makefile.am for nonrecursive libltdl build

Source: https://www.gnu.org/software/libtool/manual/html_node/Distributing-libltdl.html

Add these variable initializations and the include of libltdl/ltdl.mk near the top of Makefile.am. If other libraries are built, change lib_LTLIBRARIES to use '+=' so the libltdl targets are not overwritten.

```makefile
AM_CPPFLAGS =
AM_LDFLAGS =

BUILT_SOURCES =
EXTRA_DIST =
CLEANFILES =
MOSTLYCLEANFILES =

include_HEADERS =
noinst_LTLIBRARIES =
lib_LTLIBRARIES =
EXTRA_LTLIBRARIES =

include libltdl/ltdl.mk

```

--------------------------------

### lt_dlopenadvise

Source: https://www.gnu.org/software/libtool/manual/html_node/Libltdl-interface.html

Opens a module with additional hints provided by an advise object. The advise parameter is opaque and must be initialized with lt_dladvise_init before use.

```APIDOC
## lt_dlopenadvise

### Description
Opens a module with additional hints provided by an advise object. The advise parameter is opaque and must be initialized with lt_dladvise_init before use.

### Function Signature
`lt_dlhandle lt_dlopenadvise (const char *filename, lt_dladvise advise)`

### Parameters
- **filename** (const char *) - Required - The name of the module to open.
- **advise** (lt_dladvise) - Required - An opaque advice object containing hints for the module loader. Must be initialized with lt_dladvise_init before use.

### Returns
- **lt_dlhandle** - A handle to the loaded module, or NULL on failure. Use lt_dlerror to retrieve error message.

### Notes
- The advise parameter is passed by value, not by pointer, and is not modified by this function.
```

--------------------------------

### Enable C++ support using LT_LANG

Source: https://www.gnu.org/software/libtool/manual/html_node/LT_005fINIT.html

Example showing how to add C++ language support to Libtool using the LT_LANG macro.

```m4
LT_INIT
LT_LANG([C++])
```

--------------------------------

### foo.h header with include guard and extern "C"

Source: https://www.gnu.org/software/libtool/manual/html_node/C-header-files.html

Example from foo.h showing a header file that uses an include guard (#ifndef FOO_H) and extern "C" blocks to be compatible with C++ and C compilers.

```C
#ifndef FOO_H
#define FOO_H

#ifdef __cplusplus
extern "C" {
#endif

int foo (void);
int hello (void);

#ifdef __cplusplus
}
#endif

#endif /* !FOO_H */

```

--------------------------------

### foo.c - Library implementation

Source: https://www.gnu.org/software/libtool/manual/html_node/Windows-DLLs.html

Implementation file that defines the functions and variable declared in foo.h. It includes the header and provides the actual logic.

```c
#include "foo.h"

int one (void)
{
  return 1;
}

int two (void)
{
  return three - one ();
}

int three = 3;

```

--------------------------------

### Enable C++ support using AC_PROG_CXX

Source: https://www.gnu.org/software/libtool/manual/html_node/LT_005fINIT.html

Example showing how to add C++ language support to Libtool using the Autoconf AC_PROG_CXX macro.

```m4
LT_INIT
AC_PROG_CXX
```
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