Re: lazy load shared objects using gcc

[Fergus Henderson <fjh at cs dot mu dot OZ dot AU>]

On 10-Aug-2002, Roberta Reidel <P.R.Reidel@t-online.de> wrote:
> i always assumed 'lazy load' to be the default configuration of the
> g++/gcc 'frontend'. But i tested this using gcc version 2.96 on 
> RedHat 7.1/7.2, and it seems to be 'load now' the default configuration.
> 
> Reading the man/info pages of gcc and ld, i guess the ld to support 'lazy
> load' ( the -R <file> option ). But the gcc doesn't know any option, except
> ' -z now ' --- to *turn off* lazy loading. This confirms my assumption of 
> 'lazy load' beeing the default.
> 
> But it doesn't: The error message of missing shared libraries always appears
> on start time.

I suspect that the default behaviour is mostly-but-not-fully-lazy.
That is, it reads in the .so file and does a little bit of set up work,
but does not resolve most of the symbols.

> To decide between two hardware subsets (eg. pcmcia cards)
> i simply want to decide to engage the card of type one or two. 
> 
> a simple ' gcc MainApplication.cpp CardTypeOne.so CardTypeTwo.so ' should
> call the compiler, Assembler and linker -- preparing lazy load. But it does
> a 'load now'. (And this doubles the time to start the Application.)

Have you measured the overhead?

On modern hardware the time to link in a single .so file is very small,
and is unlikely to be worth optimizing.

-- 
Fergus Henderson <fjh@cs.mu.oz.au>  |  "I have always known that the pursuit
The University of Melbourne         |  of excellence is a lethal habit"
WWW: <http://www.cs.mu.oz.au/~fjh>  |     -- the last words of T. S. Garp.