GNU Modula-2 related environment variables

This section descibes the environment variables used by GNU Modula-2 and how they can be used to switch between releases of the compiler. Other environment variables can be set to modify the default library path. Initially we will consider environment variables most likely used by the end user. These two environment variables are GM2IPATH and GM2OPATH.

For example suppose a compile and link on the command line looks like this:

$ gm2 -g -c -I. -I../project -I../project/unix foo.mod
$ gm2 -fonlylink -g -I. -I../project -I../project/unix \
  -fobject-path=../project/obj -Iobject-path=../project/unix/obj \
  -I. foo.mod

they can be simplified by utilising two environment variables to do exactly the same compile and link.

$ export GM2IPATH=../project:../project/unix
$ export GM2OPATH=../project/obj:../project/unix/obj
$ gm2 -g -I. foo.mod

It is important to note that the two environment variables GM2IPATH and GM2OPATH have a lower priority than any -I or -fobject-path= command line option. The search order for compiling and linking is: command line switches followed by environment variable paths followed by default runtime libraries or Modula-2 dialect libraries. If in doubt include the -v option to see the search path used between the compiler subcomponents.