[TUHS] Origins of the SGS (System Generation Software) and COFF (Common Object File Format)

[arnold at skeeve.com]

Paul Winalski <paul.winalski at gmail.com> wrote:

> I can't think of any reason why ar(1) would care about the file format
> or internal contents of any of the modules it archives.  ar(1) is a
> general archiving tool and can archive anything.  It happens that the
> designers of ld(1) decided to use ar(1) to provide searchable object
> file libraries.
>
> ranlib(1) is a different matter.  In order to index global symbols it
> has to understand the object file format(s) of the modules it is
> indexing.  ranlib(1) most certainly would have to be taught to
> understand COFF.  But not ar(1).

You are correct that ar(1) was originally just an archiver. However,
the System V people built ranlib into it; the .a file for a library
has a sort of hidden extra member that is the list of symbols in
the archive.

With tar and cpio, ar apparently fell out of use as a general
archiver, and today it's only used for libraries of relocatable
object files.

Arnold