On: Fun with Glibc and the Ctype.h Functions

[jcelerier]

musl's "isalpha" is trivially wrong, for instance it wouldn't support "ç" (0xe7) or "ß" (0xdf) in ISO 8859-1 which are both alphabetic characters which fit in an unsigned char.

[tyingq → jcelerier]

Those both return 0 for isalpha() on glibc for me, with or without export LC_CTYPE=iso_8859_1

Is there some other setup I'd need to do to see it work in glibc?

[jcelerier → tyingq]

most likely you need to build the locale on your system (uncomment the relevant line in /etc/locale.gen and run sudo locale-gen).

here

  #include <ctype.h>
  #include <locale.h>
  #include <stdio.h>

  int main(int argc, char** argv)
  {
    setlocale(LC_CTYPE, "fr_FR.iso88591");
    if(isalpha('ç'))
      printf("ok\n");
  }

prints ok (with the file in the correct encoding)

[cryptonector → jcelerier]

ctype is trivially non-localizable to locales with codesets larger than sizeof(unsigned char) anyways. Maybe the problem here is POSIX.

[jcelerier → cryptonector]

oh yes, no code written in 2021 should use that mess. but a glibc being some level of posix compatibility.. hard to blame them for at least trying to make it work.

[cryptonector → jcelerier]

Hmm, well, I mean, if ctype can't work for any interesting non-ASCII (and non-EBCDIC) cases (no one should still be using ISO-8859 locales...)... maybe stop trying so hard?

[_kst_ → jcelerier]

isalpha() works with the "C" locale unless you first call setlocale().

For example, on my system isalpha(0xe7) is true if I first call setlocale(LC_ALL, "en_US.iso88591").

[jcelerier → _kst_]

well, yes, in "normal" C programs you're supposed to fetch the locale from the user's env vars (with setlocale (LC_ALL, ""))