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From: Peter Flass <peter_flass@yahoo.com>
Newsgroups: alt.folklore.computers,comp.os.linux.misc
Subject: Re: The joy of VAX C
Date: Sun, 29 Sep 2024 13:15:00 -0700
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Lars Poulsen <lars@beagle-ears.com> wrote:
> 
> 
> On 26/09/2024 18:01, Lars Poulsen wrote:
>> On 26/09/2024 13:43, Lawrence D'Oliveiro wrote:
>>> On Thu, 26 Sep 2024 11:49:37 +0100, Pancho wrote:
>>> 
>>>> On 9/26/24 11:10, Lawrence D'Oliveiro wrote:
>>>>> 
>>>>> On Thu, 26 Sep 2024 08:42:32 +0100, Pancho wrote:
>>>>> 
>>>>>> ... a bitch to work out how to call Vax C from Vax Pascal, or vice
>>>>>> versa.
>>>>> 
>>>>> Why would it be that hard? VAX C passed everything by value, while
>>>>> Pascal let you specify descriptors, references, immediate value ... all
>>>>> the options.
>>>> 
>>>> There ware decisions to be made, like what order do you push variables
>>>> onto the stack, when do you push the return address, how to interpret a
>>>> Pascal String in C.
>>> 
>>> All these things were standardized in the VAX/VMS ABI, right from the
>>> beginning.
>> 
>> IIRC, VAX C did not completely follow the standard calling conventions, 
>> which created some issues in mixed-language applications.
> 
> In retrospect, I think the problems in mixing C with other languages 
> came down to this:
> 
> For a C routine to be callable from another language, I suspect that the 
> C routine would have to declare each and every argument as a descriptor 
> structure, the use the descriptor to find the data.
> And for a C routine to call a subroutine in another language, it would 
> have to build a descriptor structure for that argument.
> 
> More trouble than anyone would want if they were used to C on any other 
> platform. Was that the right or the wrong choice?
> An extension with a keyword like "descriptor" attached to a procedure 
> prototype could have made that much easier to work with!
> 

IBM PL/I has that now. You can declare arguments descriptor/nodescriptor
and byaddr/byvalue.

 -- 
Pete