You can take a look at top comment in /usr/lib/rpm/macros Not sure what it means, however :) Cheers On Fri, Aug 31, 2012 at 11:33 PM, Björn Persson < bjorn(a)xn--rombobjrn-67a.se&gt; wrote: > As maintainer of fedora-gnat-project-common I sometimes work on RPM > macros for > use in Ada packages. Every time I define a new macro I have trouble > deciding > whether its name should begin with an underscore or not. I know that > there is > some technical difference but I've never quite understood what practical > difference it makes. > > I've been trying to imitate macros with a similar function, so I defined > _GNAT_project_dir with a leading underscore in analogy with _libdir and > others. Macros containing command line flags for build tools I've defined > without a leading underscore in analogy with optflags, but then there are > _smp_mflags and the hardening macros which have the underscore, and > __global_cflags and __global_ldflags even have two leading underscores. > > Could someone explain what difference a leading underscore makes and give > some > guidance on when I should use it? > > Is a double leading underscore functionally different from a single one, > or is > that just some kind of naming convention? > > Björn Persson > > -- > packaging mailing list > packaging(a)lists.fedoraproject.org > https://admin.fedoraproject.org/mailman/listinfo/packaging

A name is just a name, there's no functional difference. Once upon a time in a faraway galaxy there might have been, but that's nothing you need to worry about. These days its just a naming convention, albeit a rather blurry one. The bottom line: as long as your macros are "namespaced" (such as your GNAT/_GNAT prefix) to limit the possibility of clashes with others, you're technically free to call them whatever you want. Following existing conventions is not a bad idea though.