D - Passing Variables
- Rich C (5/5) Jul 25 2003 Hello,
- Russ Lewis (18/26) Jul 25 2003 Yes, but with a caveat.
- Helmut Leitner (6/8) Jul 25 2003 No, D hasn't changed this mechanism.
- Rich C (6/8) Jul 25 2003 Too bad. I am looking for a language which does not do this (other than
- Ilya Minkov (10/13) Jul 25 2003 Nope, the major reason C programs can't resist exploits are variable
- Sean L. Palmer (6/15) Jul 25 2003 Put all your data on the heap, and some a$$hole will figure out a way to
- Fabian Giesen (6/10) Jul 26 2003 Stack passing is not the problem; the problem is functions like printf
- Samuel Barber (6/9) Jul 28 2003 Are you alluding to the overwrite-the-return-address trick? There's no
- Dario (4/9) Jul 27 2003 It isn't always the case: if the function is extern(D) and the arguments...
Hello, I would like to know if D has fundamentally changed the mechanism of passing variables to functions, namely, is it still done on the stack? Thanks, Rich C.
Jul 25 2003
Russ Lewis <spamhole-2001-07-16 deming-os.org>
Yes, but with a caveat.
You cannot store (or pass) classes by value; they must be passed by
reference. All other arguments are passed by value. (Obviously, a
pointer argument is passed by the value of the pointer...
So, to create a class instance, you do it like this:
class foo{...};
foo myVar = new foo;
and when you call a function with a class argument, you pass the reference:
doThing(myVar);
However, when you use a struct, you can use the literal value:
struct bar {...};
bar myVar2; // this is a literal struct, NOT a reference
doThing2(myVar2); // this passes a copy of the struct
// on the stack
doThing3(&myVar2); // this passes a pointer to the struct
Hope this helps!
Russ
Rich C wrote:
Hello,
I would like to know if D has fundamentally changed the mechanism of passing
variables to functions, namely, is it still done on the stack?
Thanks,
Rich C.
Jul 25 2003
Rich C wrote:I would like to know if D has fundamentally changed the mechanism of passing variables to functions, namely, is it still done on the stack?No, D hasn't changed this mechanism. Yes, it is still done on the stack. -- Helmut Leitner leitner hls.via.at Graz, Austria www.hls-software.com
Jul 25 2003
"Helmut Leitner" <helmut.leitner chello.at> wrote in message news:3F218F62.DBFFA50D chello.at...No, D hasn't changed this mechanism. Yes, it is still done on the stack.Too bad. I am looking for a language which does not do this (other than assembler of course.) Hopefully someday people will realize that is is the major reason that C and C-derived programs are so susceptible to exploits. Rich C.
Jul 25 2003
Rich C wrote:Too bad. I am looking for a language which does not do this (other than assembler of course.) Hopefully someday people will realize that is is the major reason that C and C-derived programs are so susceptible to exploits.Nope, the major reason C programs can't resist exploits are variable number of arguments and the misuse of varargs functions like printf!!! This is both on the list to be dealt with in D. Besides, D makes handling heap-allocated objects easy, so that if you wish, all your valuable information will not be on a stack. Using stack is much less typical in D, since only structs and wierd extention classes are stack-allocated. Giving up stack for good would yould a very bad performance penalty, which we don't want. -i.
Jul 25 2003
Put all your data on the heap, and some a$$hole will figure out a way to printf over the vtable pointer and create an exploit. Might take him an extra hour though. Sean "Rich C" <no spam.com> wrote in message news:bfs744$10uj$1 digitaldaemon.com..."Helmut Leitner" <helmut.leitner chello.at> wrote in message news:3F218F62.DBFFA50D chello.at...No, D hasn't changed this mechanism. Yes, it is still done on the stack.Too bad. I am looking for a language which does not do this (other than assembler of course.) Hopefully someday people will realize that is is the major reason that C and C-derived programs are so susceptible to exploits. Rich C.
Jul 25 2003
Too bad. I am looking for a language which does not do this (other than assembler of course.) Hopefully someday people will realize that is is the major reason that C and C-derived programs are so susceptible to exploits.Stack passing is not the problem; the problem is functions like printf that can be abused to manipulate the stack. Besides, IMHO the major reason that C programs are so suspectible to exploits is C-style strings and related buffer overruns. Which is solved in D. -fg
Jul 26 2003
"Rich C" <no spam.com> wrote in message news:bfs744$10uj$1 digitaldaemon.com...Too bad. I am looking for a language which does not do this (other than assembler of course.) Hopefully someday people will realize that is is the major reason that C and C-derived programs are so susceptible to exploits.Are you alluding to the overwrite-the-return-address trick? There's no requirement in 'C' to store return addresses and local arrays in the same place. Sam
Jul 28 2003
Hello, I would like to know if D has fundamentally changed the mechanism of passing variables to functions, namely, is it still done on the stack? Thanks, Rich C.It isn't always the case: if the function is extern(D) and the arguments it is passed can be stored in registers, that's where they will be passed. If you're running Windows try to use obj2asm to see how they're are passed. -Dario
Jul 27 2003