On 31/01/2022 19.48, Waiman Long wrote: > On 1/31/22 05:34, Andy Shevchenko wrote: >> Also it seems currently the kernel documentation is not aligned with >> the code >> >> "If @size is == 0 the function returns 0." >> >> It should mention the (theoretical?) possibility of getting negative >> value, >> if vsnprintf() returns negative value. > > AFAICS, the kernel's vsnprintf() function will not return -1. Even if it did, the "i < size" comparison in vscnprintf() is "int v size_t", so integer promotion says that even if i were negative, that comparison would be false, so we wouldn't forward that negative value anyway. > So in that > sense it is not fully POSIX compliant. Of course it's not, but not because it doesn't return -1. POSIX just says to return that in case of an error, and as a matter of QoI, the kernel's implementation simply can't (and must not) fail. There are other cases where we don't follow POSIX/C, e.g. in some corner cases around field length and precision (documented in test_printf.c), and the non-support of %n (and floating point and handling of wchar_t*), and the whole %p<> extension etc. Rasmus
