The joy of VAX C

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:
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On 9/26/24 11:10, Lawrence D'Oliveiro wrote:

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On Thu, 26 Sep 2024 08:42:32 +0100, Pancho wrote:
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... a bitch to work out how to call Vax C from Vax Pascal, or vice
versa.

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Why would it be that hard? VAX C passed everything by value, while
Pascal let you specify descriptors, references, immediate value ... all
the options.

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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.

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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!