-fsigned-char on all arches

[Rob Landley]

On Wednesday 11 April 2007 8:42 am, Will Newton wrote:
> Hi all,
> 
> I noticed there was a change here:
> 
> 
http://www.busybox.net/cgi-bin/viewcvs.cgi/trunk/uClibc/Rules.mak?rev=13205&r1=13200&r2=13205
> 
> that enabled -fsigned-char for all arches. What was the reasoning
> behind this decision? I'm reliably informed that it generates
> suboptimal code on our architecture.

Because when it varies it's a source of bugs, and we got tired of hitting 
them.  (And yes, we hit them.)

You can specify "signed char" or "unsigned char" when you declare them, and 
lots of places do.  But gcc 4.x produces warnings whenever things "differ in 
signedness", and filling the code with typecasts to make this shut up would 
make the code brittle and unreadable and eventually introduce new bugs 
(because that thing you're typecasting to (signed char) got turned into an 
unsigned int elsewhere and all the references that produced an error or 
warning were fixed up, but the typecast prevents this one from 
complaining...)

BusyBox chose -funsigned-char because we liked being 8-bit clean.  (Makes 
things like UTF-8 a whole lot easier).  But tinycc won't work if you build it 
with -funsigned-char, which also means it won't work if you build it on an 
architecture that defaults to -funsigned-char (arm, for example).  I haven't 
tracked down the problem there yet...

Which architecture are you referring to?

Rob
-- 
Penguicon 5.0 Apr 20-22, Linux Expo/SF Convention.  Bruce Schneier, Christine 
Peterson, Steve Jackson, Randy Milholland, Elizabeth Bear, Charlie Stross...