Re: Change time_t to signed type

[bje]

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 pubs.opengroup.org 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