[Bug 269] Many compiler warnings with gcc 4.0

Frank Cusack fcusack at fcusack.com
Wed Aug 31 21:38:03 CEST 2005

On August 31, 2005 4:47:16 PM +1000 Paul TBBle Hampson <Paul.Hampson at Pobox.com> wrote:
> On Tue, Aug 30, 2005 at 01:15:45PM -0700, Steven Simon wrote:
>> I tend to think this is the wrong approach. By convention, C strings  are
>> signed and Pascal strings (I know, nobody uses them anymore) are  unsigned.
>> If char defaults to unsigned, it could cause more problems  than it solves.
>> We want the compiler to tell us if we're mixing C- strings and data buffers.

Absolutely, but this only comes into play when promoting char to int,
as is done with varargs functions, e.g. sprintf().  (There is no such
thing as a char argument to a varargs function; all chars are promoted
to int, and unsigned chars to unsigned ints.)

One common place this happens is for debug output, when printing the
contents of buffers.

<http://www.freshsources.com/1994017B.HTM> is a good page describing
the difference between signed and unsigned char.

> Chars are unsigned on Linux PowerPC. I don't believe there's anything that
> depends on chars being signed that doesn't explicitly declare such, as I ran
> FreeRADIUS on LinuxPPC without issues for a few years. I think all
> signed-char assumptions were therefore shaken out a fair while ago.

To say that chars are unsigned on Linux PPC is meaningless.  Whether chars
are signed or unsigned is up to the compiler.  Now it may be the case that
gcc on Linux PPC does treat char as unsigned, but I highly doubt it.

Linux PPC itself may have lots of code that explicitly has unsigned char
data, but that doesn't affect application code at all.  Even whether or
not glibc uses explicit unsigned char internally doesn't affect applications
since behavior must still conform to the various standards.  Wherever
char *'s are used, promotion isn't done so signed vs. unsigned doesn't
matter.  (And current standards call for void * instead of char * almost

My point is that FR running successfully on Linux PPC, which may use
unsigned char everywhere internally (I'll take your word on it) does
not imply anything about how char might be treated in application code.

Forcing unsigned char would be a mistake, IMHO.  I personally think casts
are good.  One man's ugly notation is another man's inline documentation.


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