[Info-vax] linkshrlib.com - link opensource libraries into shareable images

[Stephen Hoffman]

On 2012-08-03 15:19:36 +0000, John Reagan said:

> And I've never use match-exact in a run-time library.  Since the days 
> of SYMBOL_VECTORs, it is easy to add dummy slots to the end and even 
> more recent image activators will give really good error messages if 
> your program attempts to access of the end of the symbol vector.

But not so easy when somebody rips out an API or three in the code that 
you're porting to OpenVMS, or incompatibly reorganizes the APIs of the 
existing calls.    Case in point: OpenSSL, particularly in the 
years-long run-up to V1.0.  Now that V1.0 has arrived, the APIs might 
be more stable.  Might.

Upward compatibility is also why some APIs can and do die.  Where it 
can be easier to replace the whole thing, and leave the old to simply 
moulder.  Or to overhaul the code, and to make incompatible changes.  
Maintaining application compatibility gets expensive.  You can end up 
hoist with your own petard; with your API mistakes and omissions, and 
with expectation or technology changes.  Case in point: the eight-byte 
field that's available for the hashed password within the SYSUAF file; 
to use that with SHA-256, you'd need to scrounge another 24 bytes for 
SHA-256 (emphatically not a good password hash) or scrounge another 48 
bytes for bcrypt (vastly better password hash).  And some open source 
package APIs can change at every major version, if not some minor ones.


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