cygwin 2.4.1: broken ps_AF and ps_AF.utf8 locales

[Tony Cook <tony at develop-help dot com>]

Hi list,

Simplified to a C program below, calls to sprintf() under the ps_AF
and ps_AF.utf8 locales are returning a value that doesn't match the
length of the formatted string:

tony@phobos ~
$ cat ps_AF.c
#include <stdio.h>
#include <locale.h>
#include <string.h>

int main(int argc, char **argv) {
  char buf[100];
  char *loc = argc > 1 ? argv[1] : "ps_AF";
  const char *real_loc;
  if (!(real_loc = setlocale(LC_NUMERIC, loc))) {
    perror("setlocale");
    return 1;
  }
  printf("locale %s\n", real_loc);
  size_t len = sprintf(buf, "%g", 2.34);
  printf("len %zu\n", len);
  printf("strlen %zu\n", strlen(buf));

  return 0;
}

tony@phobos ~
$ gcc -ops_AF.exe ps_AF.c

tony@phobos ~
$ ./ps_AF
locale ps_AF
len 4
strlen 5

tony@phobos ~
$ ./ps_AF ps_AF.utf8
locale ps_AF.utf8
len 4
strlen 5

tony@phobos ~
$ ./ps_AF en_US.utf8
locale en_US.utf8
len 4
strlen 4

tony@phobos ~
$ uname -a
CYGWIN_NT-6.1-WOW phobos 2.4.1(0.293/5/3) 2016-01-24 11:24 i686 Cygwin

The man pages and C standard could be read as sprintf() returning the
number of multi-byte characters, but if cygwin is intended to follow
Linux behaviour:

tony@mars:~/play$ gcc -ops_AF ps_AF.c 
tony@mars:~/play$ ./ps_AF
locale ps_AF
len 5
strlen 5
tony@mars:~/play$ ./ps_AF ps_AF.utf8
locale ps_AF.utf8
len 5
strlen 5
tony@mars:~/play$ ./ps_AF en_AU.utf8
locale en_AU.utf8
len 4
strlen 4
tony@mars:~/play$ uname -a
Linux mars 3.16.0-4-amd64 #1 SMP Debian 3.16.7-ckt20-1+deb8u3 (2016-01-17) x86_64 GNU/Linux

(and the decimal point under ps_AF on Linux is multi-byte, character
0x66b or ARABIC DECIMAL SEPARATOR.)

POSIX is less confusing and specifies:

Upon successful completion, the sprintf() function shall return the
number of bytes written to s, excluding the terminating null byte.

(http://pubs.opengroup.org/onlinepubs/9699919799/functions/fprintf.html)

Tony


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