[PATCH 2/2] newlib/libc/time/tzset_r.c(_tzset_unlocked_r): POSIX angle bracket <> support
Brian Inglis
Brian.Inglis@SystematicSw.ab.ca
Mon Feb 28 18:55:57 GMT 2022
On 2022-02-28 05:04, Corinna Vinschen wrote:
> Hi Brian,
>
> On Feb 25 09:39, Brian Inglis wrote:
>>
>> define POSIX specified minimum TZ abbr size 3 TZNAME_MIN
>> use limits.h TZNAME_MAX, _POSIX_TZNAME_MAX, unistd.h sysconf(_SC_TZNAME_MAX)
>> issue error if no symbols defined (document fallback value in case required)
>> allow POSIX angle bracket < > quoted signed alphanumeric tz abbr e.g. <MESZ+0330>
>> allow POSIX unquoted alphabetic tz abbr e.g. MESZ
>> apply same changes for DST tz abbr
>> ---
>> newlib/libc/time/tzset_r.c | 74 ++++++++++++++++++++++++++++++++------
>> 1 file changed, 64 insertions(+), 10 deletions(-)
>>
>
>> diff --git a/newlib/libc/time/tzset_r.c b/newlib/libc/time/tzset_r.c
>> index 9e0cf834bd6b..6a5fd578c0be 100644
>> --- a/newlib/libc/time/tzset_r.c
>> +++ b/newlib/libc/time/tzset_r.c
>> @@ -1,14 +1,30 @@
>> #include <_ansi.h>
>> +#include <limits.h> /* {,_POSIX_}TZNAME_MAX */
>> #include <reent.h>
>> #include <stdio.h>
>> #include <stdlib.h>
>> #include <string.h>
>> +#include <unistd.h> /* sysconf(_SC_TZNAME_MAX) */
>> #include <sys/types.h>
>> #include <sys/time.h>
>> #include "local.h"
>>
>> #define sscanf siscanf /* avoid to pull in FP functions. */
>>
>> +#define TZNAME_MIN 3 /* POSIX specified minimum TZ abbr size */
>
> Are you sure?
Minimum is historical.
>> +/* TZNAME_MAX - POSIX specified maximum TZ abbr size */
>> +/* define TZNAME_MAX if undefined and available */
>> +#if !defined(TZNAME_MAX)
>> +#if defined(_POSIX_TZNAME_MAX)
>> +#define TZNAME_MAX _POSIX_TZNAME_MAX /* use POSIX value */
>> +#elif defined(_SC_TZNAME_MAX)
>> +#define TZNAME_MAX sysconf(_SC_TZNAME_MAX) /* use sysconf value */
>
> This is not a safe bet. _SC_TZNAME_MAX is defined in unistd.h
> unconditionally, even for targets not providing sysconf(). And
Why define indices if they are unusable on that platform?
> given that _POSIX_TZNAME_MAX is only defined for RTEMS and Cygwin,
> this will run into problems on most other targets.
>
> Only Phoenix-RTOS, RISCV, RTEMS and Cygwin support sysconf, and none
> of them actually supports _SC_TZNAME_MAX as parameter. And even Cygwin
> returns -1 and sets errno to EINVAL.
>
> Given you're checking _POSIX_TZNAME_MAX first, which is defined on
> Cygwin, the sysconf path will never be used there anyway. But that's
> actually a minor point.
>
> The real problem is, you can't use sysconf(_SC_TZNAME_MAX) like this:
> - You don't know at compile time if the function is really supported.
> - You don't know if _SC_TZNAME_MAX returns a positive value or -1.
The docs appeared unclear whether the index or return value could be -1.
POSIX sysconf(3p) man page says -1/EINVAL means invalid argument value
which should not apply if _SC_TZNAME_MAX is defined, otherwise -1/errno
is unchanged means no definite limit?!
I can just enclose it in HAVE_SYSCONF, else define a macro returning -1,
and leave it at that for our purposes, while allowing for any platform
that decides to support it.
> And then again, there's no good reason to check against _POSIX_TZNAME_MAX
> either. _POSIX_TZNAME_MAX is a system-independent definition, defining
> a *minimum* value which has to be supported by the OS. So any OS can
> define TZNAME_MAX as _POSIX_TZNAME_MAX, or any bigger value, or not at
> all, if there just is no limit.
>
> So, either the system defines TZNAME_MAX, or the system provides
> sysconf() *and* sysconf(_SC_TZNAME_MAX) returns a positive value. In
> these cases, a check against that value makes sense. In all other
> cases, there's just no limit to check for.
So I may as well default to using the hardwired limit of 10, which is
the most sensible value allowing for five letters, sign, four digits.
--
Take care. Thanks, Brian Inglis, Calgary, Alberta, Canada
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