David Schwartz wrote: >> x is still just a pointer to data - so it's the same >> length in any case, all pointers to lvalues are the >> same length in C. The only issue there is whether it's >> aligned correctly - that's the programmers problem. > > Length is not the issue. There is no rule that says that two types must be > passed the same way just because they're the same length. For example, some > platforms may pass a 64-bit floating point number in a floating point > register but pass a 64-bit integer in an integer register. > > All you can do is assume that it will work because it has always worked, > until it stops working. > >> Mixing something like char *(*d2i)(), and char ** IS >> problematic, since those aren't guaranteed to be the >> same length but as far as I can remember OpenSSL doesn't >> do that. > > If they are not the same length, it is not likely to work. That doesn't mean > it's legal if they are the same length. > >> ret=d2i(x,&p,len); > >> d2i is a function (prototype is unknown) >> but I've been told x is a pointer, &p is a pointer, >> len is long. There's nothing indeterminate about the >> size of any of those. > > The issue is not size, it's type. > >> C isn't a strongly typed language - there's no language >> requirement for an accurate function prototype or that >> the types of the arguments be correct - only that the >> size of them is correct. > > You are correct, but that's not the issue. The issue is this simple -- if > you are going to call a function whose types you don't know (through a > prototype), you must cast each type you pass to the type the function > expects. End of story. OpenSSL does not do this. This is not valid C whether > or not the type sizes are the same. > >> C is not the same language as C++, this instance should >> work with a C compiler - whether or not the compiler is >> passing the arguments via the stack or in registers. > > Can you cite anything in the C standard that says this is allowed? As I > understand it, you must pass a function precisely the types it expects, or > use a prototype to force the compiler to cast them. Either way, the exact > type must be known where the call is compiled.
It appears to me, then, that the consequence of this is that we can't have type-safety and generic functions. This strikes me as a huge pain in the ass. Surely there's some way around it? -- http://www.apache-ssl.org/ben.html http://www.links.org/ "There is no limit to what a man can do or how far he can go if he doesn't mind who gets the credit." - Robert Woodruff ______________________________________________________________________ OpenSSL Project http://www.openssl.org Development Mailing List openssl-dev@openssl.org Automated List Manager [EMAIL PROTECTED]
