Re: -funsigned-char

[Bruno Haible]

Bjarni Ingi Gislason wrote:
> > ../../gnulib-tests/test-localeconv.c:53: assertion 'l->frac_digits == 
> > CHAR_MAX' failed
> > FAIL test-localeconv (exit status: 134)
> > 
> 
> l->frac_digits is 127 and  CHAR_MAX is 255.
> 
>   This is due to the CFLAG "-funsigned-char"

When you connect a libc compiled for one ABI and a program compiled for a
different ABI (that's what -funsigned-char produces), you evidently get
breakage.

>   which I always use having
> compiled "less", which produced a lot of warnings without this flag.

The way to fix the problems occurring because a program wants to view
their strings as 'unsigned char *' is
  - NOT to use -funsigned-char, as you just have seen,
  - NOT to cast pointers from 'char *' to 'unsigned char *' and vice
    versa, because ultimately this leads to strict aliasing violations
    in some places,
  - BUT to cast individual 'char *' elements to 'unsigned char' right
    after fetching them from the string. E.g.
       if (isalnum ((unsigned char) *p))

Bruno