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e x e c . l i b r a r y FindPort
REPORT Forbid() missing, unreliable result
SEVERITY Level 2
EXPLANATION This is one of the hits that occures most. You MUST
freeze multitasking before searching through the public
list for a message port. Otherwise the port could be
shut up shortly after you've got the pointer. The next
PutMsg() will then throw Enforcer hits in best case, or
it will just trash memory. Also see AutoDocs!
DEADLY In DEADLY mode, this function call will return the
true return code only if multitasking was forbidden.
Otherwise it will pass NULL if the Port wasn't there
anyhow, or 0xFACEDEAD if the Port was found. So, just
finding out if this port existed will still work, but
accessing it will cause Enforcer hits.
REMARK Some people claim that this hit is annoying, since they
consider this practice to be legal if you only want to
find out if a port is available or not.
I don't think so. There is still a slight chance to
crash the system. Imagine your program is iterating the
list without Forbid(), looking for a certain Node B
which comes after Node A. Now, while FindPort() is
fetching Node A, a scheduling occurs and another process
gets the processor. This other process now removes Node A
from the list and changes its memory contents. If your
program then gets the processor back, it will get a
completely messed up 'Node A', and will crash.
It is sad, but as long as AmigaOS does not provide a
semaphore mechanism for public lists, we must use Forbid()
if we iterate through them.