Hallo Herr TK Chia,
am Freitag, 24. August 2018 um 18:52 schrieben Sie:
Hi all,
I think I found the cause for command crashing:
the size to swap out, and back in, is only calculated once in
XMSinit() {
...
mcb = MK_SEG_PTR (struct MCB, SEG2MCB (_psp));
xms_block_size = SwapTransientSize = mcb->mcb_size;
now if the size of command.com in memory ever changes,
to little is saved/restored.
unfortunately (thanks TK CHIA) sbreak() tries to increase the
size for malloc'ed memory. if it succeeds (and needed memory
is located behind SwapTransientSize: BAMM!
second observation:
DOSalloc(size,0) for strings puts DOS allocated memory immediately
behind command.com, preventing sbreak() from growing allocated memory,
--> somewhat better.
third observation: malloc() and sbreak() implementation will vary from
compiler to compiler, so it makes some sense to have fairly 'random'
behaviour.
I'm writing this after just thinking about the issue; no access to a
decent test machine. will test tomorrow or Tuesday.
Tom
.
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