[Info-vax] Calling standards, was: Re: Byte range locking - was Re: Oracle on VMS

[Johnny Billquist]

On 2016-11-23 18:09, Bill Gunshannon wrote:
> On 11/23/16 11:36 AM, Johnny Billquist wrote:
>> On 2016-11-23 16:54, Bill Gunshannon wrote:
>>> On 11/23/16 4:06 AM, Johnny Billquist wrote:
>>>> The C standard library use NUL-terminated strings, which (as we all
>>>> know) have serious security problems, and god knows what else.
>>>
>>> Why do people insist on perpetuating the notion that this is a C
>>> security problem.  C merely continued a practice that predated it
>>> probably to maintain compatability with earlier code.
>>
>> It *is* a C security problem. That does not imply that it isn't a
>> problem elsewhere as well, but trying to deny that this is a problem in
>> C is silly. And it certainly does not imply that the problem only
>> appeared with C. But it still is a problem in C...
>
> Of course it's a C problem.  But people seem to think that C caused it.
> C merely chose to not violate an existing practice.  It would not
> surprise me to find out that the .ASCIZ directive directly influenced
> the choice to use null terminated strings in C.  But I guess we'll
> never know.

I doubt that anything in MACRO-11 in any way reflected on anything in C 
or vice versa.

Using NUL as a terminator was, as you mention, not unheard of. RT-11 
does it. So does other systems. So, having MACRO-11 capable of creating 
such strings is no surprise.

Having C strings being terminated by NUL is also no big thing. But C and 
Unix took their cues from other sources than DEC. Multics, BCPL, B... 
There are many things to look at.

>>> The PDP-11 Macro Directive .PRINT takes a null terminated string
>>> as its only argument.  I suspect the VAX had the same and it
>>> probably still exists in MACRO but I don't have my manual handy to
>>> verify that.
>>
>> The *RT-11* Macro Directive .PRINT takes a null terminated string. Not
>> PDP-11 MACRO in general. Try that on RSX, and you'll just get an error
>> when assembling... :-)
>>
>
> True.  I just looked in my RSTS manual and the RSX executive doesn't
> have .ANYTHING directives at all.  Now I have to go look at some of
> my other manuals and see just who else used null terminated strings.
> UNIVAC-1100 did not.  It, too, had descriptors.  I have a number of
> other assembler manuals be interesting to know just how many used
> null termination as a common method.  I know it was fairly common
> in Z80 code i worked with even before a C compiler became common.

In most processors, using a NUL to indicate the end of a string makes it 
efficient to write the code. So you'll probably see it on almost any 
architecture where people want to deal with dynamic length strings.

The other alternative is to keep a count, but that uses more memory, and 
in some cases adds a bit of complexity, which people often try to avoid 
(programmers being lazy and all).

But Unix, as well as RSX and VMS, do not have any OS interfaces that use 
NUL terminated strings. Library functions on the other hand might...

	Johnny