From: Alejandro Colomar > Sent: 02 October 2020 09:25 > > For 'void *' you should also mention that one cannot use arithmetic on > > void * pointers, so they're special in that way too. > > Good suggestion! Except that is a gcc extension that is allowed in the kernel. > > Also, you should > > warn that because one can convert from any pointer type to void * and > > then to any other pointer type, it's a deliberate hole in C's > > type-checking. > > Also good. I'll talk about generic function parameters for this. That isn't what the C standard says at all. What is says is that you can cast any data pointer to 'void *' and then cast it back to the same type. This matters because the compiler will 'remember' structure alignment through 'void *' casts. So you can't use memcpy() to copy from a potentially misaligned (typed) pointer. 'void *' should only be used for structures that are 'a sequence of bytes'. (eg things that look a bit like read() or write()). David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)
