Hi Mark, On Thu, Apr 06, 2023 at 02:56:28PM +0100, Mark Brown wrote: > At present the kselftest header can't be used with nolibc since it makes > use of vprintf() which is not available in nolibc and seems like it would > be inappropriate to implement given the minimal system requirements and > environment intended for nolibc. In fact we already have vfprintf(), and printf() is based on it, so wouldn't it just be a matter of adding vprintf() that calls vfprintf() for your case ? Maybe just something like this : static int vprintf(const char *fmt, va_list args) { return vfprintf(stdout, fmt, args); } It's possible I'm missing something, but it's also possible you didn't find vfprintf() which is why I prefer to raise my hand ;-) > This has resulted in some open coded > kselftests which use nolibc to test features that are supposed to be > controlled via libc and therefore better exercised in an environment with > no libc. Yeah that's ugly. In nolibc-test we now have two build targets so that we can more easily verify the compatibility between the default libc and nolibc, so my recommendation would be to stick to a common subset of both libcs, but not to rely on nolibc-specific stuff that could make tests harder to debug. Regards, Willy