TZif v1 encodes its version as NUL, but do_tzset treats only the byte '1' as v1. It consequently reads a valid v1 file as if it contained a second header. Use zero and nonzero version bytes to distinguish v1 from later files.
commit cb0cdc2e88c652af225d2fc31c1dec99b9880d39 broke this as part of future proofing.
this fixes a build regression for riscv32 introduced in commit b306b16af15c89a04d8e0c55cac2dadbeb39c083. prior to that, the riscv32 bits/syscall.h.in defined a macro for the nanosleep syscall, despite the kernel on time64-native archs having no such syscall. our clock_nanosleep uses the old nanosleep syscall when possible as part of minimal compatibility with pre-2.6 kernels. using a non-functional syscall number didn't have any ill effect on riscv32 or future time64-native archs, since the affected code is unreachable in that case, but removing the wrongly defined macro broke the build. this change fixes it. in order not to need to fix this again if future 64-bit archs also drop the old nanosleep syscall factor out the conditional use of SYS_nanosleep and use the same approach in the preprocessor else block for them.
mktime is required to accept and normalize out-of-range members of struct tm. When tm_mday is INT_MIN, subtracting one from it overflows before the existing long long multiplication takes effect. Perform the subtraction in long long so the complete int range can be normalized as intended.
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.