Re: warning in 'base64' module

[Simon Josefsson]

Bruno Haible <address@hidden> writes:

> The base64 module has a warning on Linux/glibc:
>
> gcc -DHAVE_CONFIG_H -I. -I/packages/megatestdir/base64/lib -I..     -g -O2 -c 
> /packages/megatestdir/base64/lib/base64.c
> /packages/megatestdir/base64/lib/base64.c: In function `isbase64':
> /packages/megatestdir/base64/lib/base64.c:284: warning: comparison is always 
> true due to limited range of data type

Caused by:

static const signed char b64[0x100] = {
...
bool
isbase64 (char ch)
{
  return to_uchar (ch) <= 255 && 0 <= b64[to_uchar (ch)];
}

mentioned in:

http://article.gmane.org/gmane.comp.lib.gnulib.bugs/2694/match=base64+comparison+true+limited+range+data+type

Presumably the warning is because gcc believe an unsigned char cannot
be larger than 255, but we didn't want to assume that since I don't
think C89 guarantee it.  Correct me if I'm wrong...

Is there a clean fix?