🚀 go-pugleaf

The following problem came up while writing a resizable ramdisk.  What
I wanted was a ramdisk which could be installed, resized, and
deinstalled without causing a reboot of the system and without losing
memory blocks.  The idea was to break it into two parts: a small
memory-resident driver program and an ordinary transient program RD to
interact with the user and allocate/deallocate memory for the ramdisk.

The problem is, how can RD allocate a memory block that outlives the
invocation of RD, for GEMDOS automatically frees all memory allocated
by a process when it terminates.  I have found two hacks which both seem
to work, but both violate official Atari specs for safe programming:

1.  After allocating the block, search GEMDOS's memory allocation
chain to find the descriptor of the just-allocated block, and change
its owner field to that of the oldest process in the process list.
That way, the block is not recognized as being owned by RD and is not
freed when RD terminates. 

2.  Change Gemdos's current process pointer to point to the oldest
process in the process list, Malloc the memory block, and then restore
the current process pointer.  Again, the memory block ends up looking
like it belongs to some other process and hence is not freed when RD
exits. 

In both cases, the memory can be subsequently freed by a reverse of
the above, namely, force the block's owner to agree with the current
process pointer and then call Mfree. 

The first method requires the undocumented location of the head of the
memory allocation chain and also relies on internal Gemdos data
structures.  The second method uses a location that has been newly
documented in TOS 1.4, but it involves writing to that location, which
is not supported. 

Question:  Is there a supported way of accomplishing this?

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| Michael Fischer                                |
|    Arpanet:    <fischer-michael@cs.yale.edu>   |
|    Bitnet:     <fischer-michael@yalecs.bitnet> |
|    UUCP:       <fischer-michael@yale.UUCP>     |
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==================================================
| Michael Fischer                                |
|    Arpanet:    <fischer-michael@cs.yale.edu>   |
|    Bitnet:     <fischer-michael@yalecs.bitnet> |
|    UUCP:       <fischer-michael@yale.UUCP>     |
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