+1 :-) -- CeDeROM, SQ7MHZ, http://www.tomek.cedro.info
On Mon, May 4, 2026 at 12:07 PM Nathan Hartman <[email protected]> wrote: > > One of the nicest things about NuttX is that you can use it with any > microcontroller. That's the biggest selling point for me: instead of using > a different set of vendor libraries for each microcontroller, you can > standardize on NuttX and your code becomes portable across microcontrollers > regardless of vendor. > > If we start leaving microcontrollers behind, first it will be 8-bit > microcontrollers, then likely it will be 16-bit, eventually we'll be a > large and heavy OS that only works on powerful, expensive chips. > > I like the idea of 64-bit time_t being the default with a way to reduce it > when appropriate for a particular use case. The Kconfig "---help---" text > could warn that less than 64-bit is non-POSIX and the consequences of using > less than 64 bits, and let the developer decide. By default we'll be > 64-bits and complying with POSIX on this issue. > > My 2¢... > > Nathan > > On Mon, May 4, 2026 at 7:43 AM Alan C. Assis <[email protected]> wrote: > > > I wasn't aware that libfaketime was facing an issue with the time_t moving > > to 64-bit ? > > > > https://github.com/wolfcw/libfaketime/issues/418 > > > > I think in our case we don't have any issue (I hope), other than the code > > increasing and a worse performance on 8/16/32-bit MCUs. > > > > BR, > > > > Alan > > > > On Sun, May 3, 2026 at 4:22 PM Gregory Nutt <[email protected]> wrote: > > > > > There are some compilers that do not support uin64_t natively. For > > those, > > > library support would be needed. > > > > > > If an implementation requires multiple accesses to read/write uint64, > > then > > > the accesses would be non-atomic. At a bare minimum, the locked section > > > would be required (which would not prevent concurrent accesses from > > > interrupt handlers). > > > > > > I support the POSIX first prioritization. I removed a lot of support > > > needed by some of these architectures in the past for similar reasons. > > > That broke certain compilers and a lot of implementations (which are > > still > > > broken). We should probably do the same, but with full awareness of > > > functionality well will use or things that are very broken. > > > > > > I have suggested removing support for the 8 bit architectures and for > > > compilers like the ZDS and SDCC compilers. Carrying architectures with > > > this level of breakage is misleading. > > > > > > ________________________________ > > > From: [email protected] <[email protected]> > > > Sent: Sunday, May 3, 2026 9:42 AM > > > To: [email protected] <[email protected]> > > > Subject: Re: [DISCUSS] Removal of CONFIG_SYSTEM_TIME64 and make time_t > > > 64-bit by default > > > > > > Hello, > > > > > > I tried for AVR128DA28 - tools/configure.sh -l breadxavr:nsh > > > > > > Default setting (CONFIG_SYSTEM_TIME64 not set): > > > > > > Register: nsh > > > Register: sh > > > LD: nuttx > > > Memory region Used Size Region Size %age Used > > > flash: 50457 B 128 KB 38.50% > > > sram: 636 B 16 KB 3.88% > > > eeprom: 0 B 512 B 0.00% > > > rodata: 592 B 4 KB 14.45% > > > CP: nuttx.hex > > > CP: nuttx.asm > > > > > > With CONFIG_SYSTEM_TIME64 set: > > > > > > Register: nsh > > > Register: sh > > > LD: nuttx > > > Memory region Used Size Region Size %age Used > > > flash: 52307 B 128 KB 39.91% > > > sram: 668 B 16 KB 4.08% > > > eeprom: 0 B 512 B 0.00% > > > rodata: 592 B 4 KB 14.45% > > > CP: nuttx.hex > > > CP: nuttx.asm > > > > > > 2kB seems quite noticeable for a chip with 128kB flash. Runtime costs > > > are somewhat hard to assess, the time_t type is used in internal > > > timekeeping but the code was developed with tickless mode of operation > > > in mind so the timekeeping functions should not run that often unless > > > the system gets busy with processing lots of timed events. > > > > > > As for the benefits - the real question is how many devices (designed > > > with a chip like this one) need to know real time and therefore handle > > > year 2038. (None of my use cases need that.) > > > > > > So for small systems, having the option to configure NuttX so time_t is > > > 32 bit wide would certainly be beneficial. Making the SYSTEM_TIME64 > > > option default to DEFAULT_SMALL would be nice but it's not POSIX-correct > > > so I don't think that's gonna fly. > > > > >
