Hi,
I don't quite agree with Per's explanation, at least not as far as
SMSQ/E is concerned.
Once the memory is allocated, A0 points past the header, as Per said.
So, at -4(a0) you will find chp_flag, not chp_len.
Moreover, chp_flag is used by the system :
Consider how SMSQ/E releases memory reserved on the common heap
(in smsq_mem_rchp_asm)
movem.l reglist,-(sp) save volatiles
moveq #chp.free,d0
move.l d0,chp_ownr(a0) set owner free
move.l chp_flag(a0),d0 flag address
beq.s mrc_rehp is empty, do nothing
move.l d0,a1 set flag...
st (a1) ...now
*
So what happens here is that, if chp_flag isn't empty, the address
it points to will have its MSB set. If you put "grab" in there, then
address $67726162 will have its MSB set to 1.
OK, that most likely won't be a problem because in most cases that
address doesn't exist. But what if you put something else than "grab" at
chp_flag and that points to somewhere in real memory? Oops...
So your initial way of doing things definitely is the right way.
HTH
Wolfgang
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