Prime C pointers

[Lee McLoughlin]

>> From:  Bob Larson <BLARSON at ecld.#eclnet>
>> 
>> When casting a pointer (48 bits) to an integer or long (32 bits) using
>> Prime C, it is changed into a byte address (not useful to prime hardware/
>> microcode) and the extra information (fault and ring) is apparently
>> dropped.
>Pointers are 32 bits on the prime, not 48. The problem is that the
>ring information is stuffed in the upper 4 (or 5, I'm not sure)
>bits. I ran into this problem when I converted lots of unix programs
>that contained functions defined like
>func(args)
>and returned pointers.
Commonly address on the Prime (in the 50 range) are held in 32 bits.  This
is because they are mainly word pointers.  But you can have a character
pointer which is 48 bits long.  There is a bit in the word pointer which
tells the hardware wether to bother with the extra 16 bits of the address
or not.  If you use this bit to represent hi/lo byte then you can use the
32 bit pointer to point at characters.  This, of course, confuses everyone.
>
>By the way, we have the C compiler sold by Prime, but it's *very*
>slow (spelled SSSSSSSSLLLLLLLLOOOOOOOsnore). Does anyone know of
>a better C implementation, running under PRIMOS rev 19?
>
>	Jack Jansen, {philabs|decvax}!mcvax!vu44!jack
I did a C compiler for our Prime.  The compiler itself it pretty fast.
However it generates PMA (Prime Macro Assembler) and *BOY* is that assembler
slow!

Pointers on Primes are generally a real barrel of laughs.
Good test of portability,  miss out a cast and your proggy will dump on you.
-- 
--------------
Lee McLoughlin	<UK>!ukc!lmcl, west44!lee
	UKUUCP support.