It isn't only glibc, many other libc implementations(e.g. musl, newlib, bionic) follow this convention. I think 64bit time_t should be fine to change to signed integer, but keep 32bit time_t as before.
On Tue, Nov 5, 2024 at 4:51 AM <b...@the-wanderers.org> wrote: > Hi Guiding, > > Both your reference and the Open Group specification documents both only > state that POSIX requires time_t to be an integer type, not a signed > integer. > > The Open Group Base Specifications Issue 8 > <https://pubs.opengroup.org/onlinepubs/9799919799/> > pubs.opengroup.org <https://pubs.opengroup.org/onlinepubs/9799919799/> > [image: favicon.ico] <https://pubs.opengroup.org/onlinepubs/9799919799/> > <https://pubs.opengroup.org/onlinepubs/9799919799/> > > GNU libc additionally mandates a signed integer but notes this is a GNU > extension and not a POSIX requirement. > > The 2024 edition of POSIX has introduced a requirement for time_t to be 64 > bits. As has already been noted this is itself a substantial change. > > Byron > > On 4 Nov 2024, at 11:33 PM, Guiding Li <ligd...@gmail.com> wrote: > > Hi all: > > We decide change 'time_t' from unsigned type to signed type in PR: > https://github.com/apache/nuttx/pull/14460 > > Because when compile some POSIX library, there always be a warning on > comparison > between time_t and zero. > > For example: > > The following code will generate warnings: > auto now = time(nullptr); > auto last_active_time = GetEventService(self->ctx_)->getActiveTime(); if > (last_active_time + 60 * 1000 / 1000 <= now) { > > src/ams/../controller/controller_timer.h: In lambda function: > src/ams/../controller/controller_timer.h:117:57: warning: comparison of > integer expressions of different signedness: 'long long int' and 'long long > unsigned int' [-Wsign-compare] > 117 | if (last_active_time + 60 * 1000 / 1000 <= now) { > > > And we can find an reference on the official website: > > https://www.gnu.org/software/libc/manual/html_node/Time-Types.html > > On POSIX-conformant systems, time_t is an integer type. > > > The comparation of the merits and shortcomings: > > Advantage: > For the most POSIX applications they assume the time_t as signed and do > compare with 0. > The code will become more compatible after this modification. > > Disadvantage: > None. > > > If there is any question about this, please let me know. > Thanks, > Guiding > >
