exporting argc/argv to applets

[Rich Felker]

On Thu, Jul 06, 2006 at 11:59:37AM -0400, Rob Landley wrote:
> On Sunday 02 July 2006 9:36 am, Bernhard Fischer wrote:
> > Hi,
> >
> > FYI, I've been pondering ¹) landley's suggestion to export argc
> > and argv globally, so we wouldn't have to pass it around as arguments.
> >
> > From a cursory look, this doesn't seem to be a good idea, though:
> 
> I didn't say it was a good idea, just an idea. :)
> 
> >    text	   data	    bss	    dec	    hex	filename
> >  862418	  10156	 644740	1517314	 172702	busybox.old
> >  865586	  10156	 644708	1520450	 173342	busybox
> >
> > Could very well be that i did something wrong/incomplete, admittedly.
> 
> On x86 especially, registers are a scarce resource.  It turns out to be 
> smaller to deal with all stack variables (sp+offset) or all global variables 
> (bp+offset).

Global variables are not bp+offset, just fixed address. The difference
in size to access them is that sp+offset requires only one byte for
the offset when it fits in a (signed) byte, but global variables will
always have their addresses coded as 4 bytes.

> Switching back and forth between the two seems to result in 
> bigger code.  I dunno if it confuses the optimizer or if it's just a hard 
> problem in a register starved environment like x86.

Never observed this.. can you elaborate?

> I'd have thought the savings from yanking the arguments from all the main() 
> functions would have overcome that, though...

Yes I'm a bit surprised too...

Rich