Hi Everyone, Some years ago NuttX was able to fit in really small MCUs (in fact I got it running on a chip using less than 2KB RAM).
But a few years ago those options to disable SIGNALS, VFS, etc were disabled to create a system that was fully POSIX compliant. Unfortunately we missed the details: POSIX also aims at systems without resources, as is the case of POSIX PE51 (POSIX PSE51 is a specific, minimal profile or subset of the full POSIX - Portable Operating System Interface standard, formally defined in IEEE 1003.13-2003). Almost two years ago I opened an issue about it: https://github.com/apache/nuttx/issues/11390 Today Mr Chengdong opened a PR to bring back the possibility to disable signals: https://github.com/apache/nuttx/pull/17352 But as Mateusz (raiden00pl) pointed we need to be careful about it to avoid breaking the Inviolables: ## Strict POSIX compliance - Strict conformance to the portable standard OS interface as defined at OpenGroup.org. * - A deeply embedded system requires some special support. Special support must be minimized.* - The portable interface must never be compromised only for the sake of expediency. - Expediency or even improved performance are not justifications for violation of the strict POSIX interface. Fortunately Greg chose well his words: "Special support must be minimized". It doesn't mean it could exist, we just need to take care to not become normal or goal and jeopardize the system. So in this sense I propose to vote a suggestion: In the configuration where we already add an option to disable posix timer, pthreads, etc we add an option to "Enable POSIX PE51 subset". This way someone willing to disable signals will be aware he/she is creating a system that is not POSIX fully compliant or it is just a subset of a POSIX OS. BR, Alan
