Re: [TUHS] Deleted lib1 and lib2 in v6, recoverable?

[<ron@ronnatalie.com>]

Yes, it pretty much has to be this way as it is a single pass process and the ar format is simple.
The later libraries have a symbol "dictionary" added to the beginning.   Before that you manually arranged the order of the relocatables in the library and later automated tools to put them in dependency order (ranlib, etc...) came about.


> -----Original Message-----
> From: TUHS <tuhs-bounces@minnie.tuhs.org> On Behalf Of Paul Winalski
> Sent: Sunday, December 30, 2018 1:34 PM
> To: Noel Chiappa <jnc@mercury.lcs.mit.edu>
> Cc: tuhs@minnie.tuhs.org
> Subject: Re: [TUHS] Deleted lib1 and lib2 in v6, recoverable?
> 
> On 12/28/18, Noel Chiappa <jnc@mercury.lcs.mit.edu> wrote:
> >
> > If so, the thing is that the V6 linker won't pull in an object module
> > from a library unless a global in it satisfies an already existing
> > (i.e. in the linking process) undefined global. (I don't know if this
> > is true of later linkers; never used 'em.)
> 
> I think this has been pretty much universal behavior for all linkers on all OSes
> since the 1960s.  It continues to be true today.
> 
> Sometimes one runs into a situation where a module loaded from lib1.a has
> an undefined symbol that causes a module from lib2.a to be loaded, and that
> module in turn has an undefined symbol that is defined in lib1.a.  In that
> case, you have to cause the linker to scan lib1.a
> twice:
> 
>     ld main.o lib1.a lib2.a lib1.a
> 
> -Paul W.