there are three issues here: 1. if tzset has not been called (explicitly or implicitly), the tzname[] array will contain null pointers, and the dereference to compare against them has undefined behavior (and will fault). 2. access to tzname[] was performed without the timezone lock held. this resulted in a data race if the timezone is concurrently changed from another thread. 3. due to unintended signedness of the types, the open-coded isalpha in the non-matching case was wrong and would continue past null termination. to fix the first two issues, the body of the %Z conversion is moved to __tz.c where it has access to locking, and null checks are added. there is probably an argument to be made that the equivalent of tzset should happen here, but POSIX does not specify that to happen, so in the absence of an interpretation adding such an allowance or requirement, it is not done. the third issue is fixed just by using the existing isalpha macro.
previously, we left any changes made by the application to the timer thread's signal mask active when resetting the thread state for reuse. not only did this violate the intended invariant that timer threads start with all signals blocked; it also allowed application code to execute in a thread that, formally, did not exist. and further, if the internal SIGTIMER signal became unblocked, it could also lead to missed timer expiration events.
commit 6ae2568bc2367b4d47e0ea1cb043fd56e697912f introduced a fatal signal condition if the internal timer signal used for SIGEV_THREAD timers is unblocked. this can happen whenever the application alters the signal mask with SIG_SETMASK, since sigset_t objects never include the bits used for implementation-internal signals. this patch effectively reverts the breakage by adding back a no-op signal handler. overruns will not be accounted if the timer signal becomes unblocked, but POSIX does not specify them except for SIGEV_SIGNAL timers anyway.
our pthread barrier implementation reportedly has bugs that are could lead to malfunction or crash in timer_create. while this has not been reviewed to confirm, there have been past reports of pthread barrier bugs, and it seems likely that something is actually wrong. pthread barriers are an obscure primitive, and timer_create is the only place we are using them internally at present. even if they were working correctly, this means we are imposing linking of otherwise likely-dead code whenever timer_create is used. a pair of semaphores functions identically to a 2-waiter barrier except for destruction order properties. since the parent is responsible for the argument structure (including semaphores) lifetimes, the last operation on them in the timer thread must be posting to the parent.
having it in __tz.c caused gmtime[_r] and timegm to pull in all of the time zone code despite having no need for it.
the %s conversion is added as the outcome of Austin Group tracker issue 169 and its unspecified behavior is clarified as the outcome of issue 1727. the %F, %g, %G, %u, %V, %z, and %Z conversions are added as the outcome of Austin Group tracker issue 879 for alignment with strftime and the behaviors of %u, %z, and %Z are defined as the outcome of issue 1727. at this time, the conversions with unspecified effects on struct tm are all left as parse-only no-ops. this may be changed at a later time, particularly for %s, if there is reasonable cross-implementation consensus outside the standards process on what the behavior should be.
commit f47a5d400b8ffa26cfc5b345dbff52fec94ac7f3 overlooked that strtoul was responsible for setting p to a const-laundered copy of the format string pointer f, even in the case where there was no number to parse. by making the call conditional on isdigit, that copy was lost. the logic here is a mess and should be cleaned up, but for now, this seems to be the least invasive change that undoes the breakage.
strtoul will consume leading whitespace or sign characters, which are not valid in this context, thereby accepting invalid field specifiers. so, avoid calling it unless there is a number to parse as the width.
The lifetime of the compound literal ends after the "if" statement's implicit block. gcc also warns about this.
C11 6.11.5p1: > The placement of a storage-class specifier other than at the > beginning of the declaration specifiers in a declaration is an > obsolescent feature. gcc also warns about this.