B.3 Compiling gdb in Another Directory
If you want to run gdb versions for several host or target machines,
you need a different
gdb compiled for each combination of
host and target. configure is designed to make this easy by
allowing you to generate each configuration in a separate subdirectory,
rather than in the source directory. If your
handles the VPATH feature (gnu
make does), running
make in each of these directories builds the
program specified there.
gdb in a separate directory, run configure
with the --srcdir option to specify where to find the source.
(You also need to specify a path to find configure
itself from your working directory. If the path to configure
would be the same as the argument to --srcdir, you can leave out
the --srcdir option; it is assumed.)
For example, with version 7.2, you can build gdb in a separate directory for a Sun 4 like this:
cd gdb-7.2 mkdir ../gdb-sun4 cd ../gdb-sun4 ../gdb-7.2/configure sun4 make
When configure builds a configuration using a remote source directory, it creates a tree for the binaries with the same structure (and using the same names) as the tree under the source directory. In the example, you'd find the Sun 4 library libiberty.a in the directory gdb-sun4/libiberty, and gdb itself in gdb-sun4/gdb.
Make sure that your path to the configure script has just one instance of gdb in it. If your path to configure looks like ../gdb-7.2/gdb/configure, you are configuring only one subdirectory of gdb, not the whole package. This leads to build errors about missing include files such as bfd/bfd.h.
One popular reason to build several gdb configurations in separate directories is to configure gdb for cross-compiling (where gdb runs on one machine—the host—while debugging programs that run on another machine—the target). You specify a cross-debugging target by giving the --target=target option to configure.
When you run
make to build a program or library, you must run
it in a configured directory—whatever directory you were in when you
called configure (or one of its subdirectories).
Makefile that configure generates in each source
directory also runs recursively. If you type
make in a source
directory such as gdb-7.2 (or in a separate configured
directory configured with --srcdir=dirname/gdb-7.2), you
will build all the required libraries, and then build GDB.
When you have multiple hosts or targets configured in separate
directories, you can run
make on them in parallel (for example,
if they are NFS-mounted on each of the hosts); they will not interfere
with each other.