2013/11/7 Szabolcs Nagy <n...@port70.net>: > * Alexander S. <alex0pla...@gmail.com> [2013-11-07 04:27:26 +0400]: >> Seriously, simple parametric types wouldn't hurt C. Not at all. No >> need for that automatic pointer conversion, additional parameters to >> sort() and alike, and such. (I'm going to make a confession, I really >> think C would benefit from C++ templates, even in their current >> state). > > c has no implicit pointer conversion other than for void* > > void* is important to represent pointers in a generic way, > parametric types do not help with this, those assume a > statically known type which is not always the case > > the way c++ eliminated the implicit conversion is actually > less safe than the c semantics: in c++ one has to use casts > to convert void* and this turns off the type-checker > > there are plenty source for void pointers: mmap, dlsym, > context pointers for callbacks, etc. if you incorrectly > assume in c that a pointer is void* then you get a type error, > in c++ your cast will mask this error so it can go unnoticed, > in c a cast is a code smell that alarms you, in c++ they are > not uncommon at all in code interacting with the os, actually > c++ has at least 4 different casts with different semantics > based on what you cast, this is not how to improve safety
Well, in code interacting with low-level you are probably going to meet just static_cast<>, which is everywhere, and reinterpret_cast<>, that's reserved for casting pointers. I can argue about necessity of these four types of casts (dynamic_cast<> is quite important for safety, imo). Context pointers for callbacks... well, they exist because of the limitations of the type system. I'd rather see ЛA,[Types...].pthread_create(pthread_t*, A(*callback)(Types...), Types args...) (so, arbitrarily many additional args for callbacks). A type-checker can properly check it, and even in current calling conventions, it's quite fast to handle: you just copy a chunk of memory fro and to stack, wholesale. Failing that, there's always ЛA,B.pthread_create(pthread_t*, A(*callback)(B), B arg). mmap is another matter, but whether for turning file into RAM or for IPC, it tends to have some structure, I guess? > parametric types have problems on their own: eg the type > parameters have to be encoded into the name of the interface > which gives rise to name mangling with all its warts > (c++ name mangling is not specified so you get a fragile binary > interface with names so long that the hash lookups by the elf > dynamic loader becomes a bottleneck..) -- Best regards, Alexander S.
