It makes little sense to talk about using libtool in your own packages until you have seen how it makes your life simpler. The examples in this chapter introduce the main features of libtool by comparing the standard library building procedure to libtool’s operation on two different platforms:
An Ultrix 4.2 platform with only static libraries.
A NetBSD/i386 1.2 platform with shared libraries.
Source files for the following examples are taken from the Autotest file tests/demo.at. The files can be extracted by running a demo test and preserving the artifacts:
burger$ make check TESTSUITEFLAGS="-d -k 'preloaded static library'" burger$ cp -r tests/testsuite.dir/027 demo/
You can follow these examples on your own platform, using the preconfigured libtool script that was installed with libtool (see Configuring libtool). Assume that we are building a library, libhello, out of the files foo.c and hello.c.
Note that the foo.c source file uses the cos math library
function, which is usually found in the standalone math library, and not
the C library (see Trigonometric Functions in The GNU C Library Reference Manual). So, we need to add -lm to
the end of the link line whenever we link foo.lo into an
executable or a library (see Inter-library dependencies).
The same rule applies whenever you use functions that don’t appear in the standard C library… you need to add the appropriate -lname flag to the end of the link line when you link against those objects.
After we have built that library, we want to create a program by linking main.o against libhello.