[Info-vax] C History on VMS (was Re: C... the only winning move is not to play...)

[JohnF]

Stephen Hoffman <seaohveh at hoffmanlabs.invalid> wrote:
> On 2014-02-12 15:34:35 +0000, JohnF said:

Thanks for the "history and discussion" below
(you should maybe write a book, if there isn't already one)...

>> ...I think dcl is what all those str$functions we discussed were really 
>> written for. That is, but for digital's desire to provide string 
>> manipulation in dcl, they never would have bothered with that 
>> str$library. The C headers and stuff were more of an afterthought, 
>> i.e., as long as the library's there, might as well let C link it. But 
>> all other things equal, when writing C you're better advised to use 
>> standard C stuff if possible.
> 
> Some history and discssions of general and related structures...
> 
> DCL has its own supervisor-mode world; getting stuff compiled and 
> linked into that environment is a little odd. (It and the XQP are 
> probably two of the weirder parts of VMS, in terms of its general 
> run-time environment, and around debugging it.)
> 
> FWIW, none of the VMS and none of the (user-mode) language RTLs are 
> intended to be callable from any inner-mode code. (There were (are) 
> some security-clobbering hacks latent in the RTL calls that allowed 
> inner-mode to sort-of kind-of work, for those folks that were inclined 
> to open up leaks across the per-mode memory management protections.  
> Not recommended.)
> 
> I don't have the OpenVMS source listings handy to confirm it, but I'd 
> be surprised if there were RTL calls around.
> 
> As for the include files, the VMS-provided header files are common 
> source.  The same SDL source file generates C, BASIC, Fortran and 
> others, and ? with the most recent versions of SDL ? also now DCL 
> symbolic constants.  C was added to this list over time, and 
> particularly around the addition of the SYS$STARLET_C and SYS$LIB_C 
> libraries into OpenVMS.  STARLETSD.TLB was also used by various 
> languages.
> 
> In terms of the per-language support within OpenVMS, C was effectively 
> an afterthought for most of the environments, as the first C compiler 
> and VAXCRTL library support only arrived somewhere around V4.4 IIRC.  
> That was well after the other languages.   C is also somewhat weird on 
> OpenVMS in that it now has two libraries; the traditional user-mode 
> library that most languages have, and also its own kernel-mode library 
> that was implemented as part of the C system programming support that 
> arrived around OpenVMS V6.1 IIRC.
> 
> The STR$ and LIB$ calls are generally old.  Many of the core routines 
> are older than V4.4.  It wouldn't surprise me to learn that the history 
> of this stuff goes back further than VAX-11/VMS too, as here's the 
> XPORT library for TOPS 
> <http://bitsavers.informatik.uni-stuttgart.de/pdf/dec/pdp10/TOPS10_softwareNotebooks/vol08/AA-J201A-TK_XPORT_Programmers_Guide_Apr81.pdf> 
> 
> The STR$ and LIB$ calls are useful in Macro, Bliss, Fortran and various 
> other languages.  (Various Fortran code was is still fond of using 
> space-padded fixed-length strings, too.)  The OTS$ calls was largely 
> for the compilers, but was and is available for other use.
> 
> More to make it a little easier for me to find these details for some 
> hypothetical next time a discussion of ancient VMS calls and ancient 
> run-time libraries (RTLs) arises, there are all sorts of related 
> shenanigans around the break-up of the VMSRTL run-time library are in 
> play here, too.  The ancient VMSRTL omnibus library has a long and 
> checkered career: 
> <http://archive.org/stream/bitsavers_decvaxvms2ReleaseNotesMar80_3242450/AA-D015C-TE_VMS_2.0_Release_Notes_Mar80_djvu.txt> 
> <http://archive.org/stream/bitsavers_decvaxvms3leaseNotesV3.0May82_5458871/AA-D015D-TE_VAX-VMS_Release_Notes_V3.0_May82_djvu.txt> 
> <http://www.ibiblio.org/pub/academic/computer-science/history/pdp-11/hardware/micronotes/numerical/micronote36.txt>. 
> This VMSRTL stuff was in common use prior to VAX/VMS V4.0, when that 
> RTL was broken up into hunks; into separate RTLs.  For completeness, 
> this was all before C existed on VMS, too.

-- 
John Forkosh  ( mailto:  j at f.com  where j=john and f=forkosh )