mema takes a count of bytes, but memw and memr both take a count of items. So
if you want space for y integers, you need mema y*8 (or, if scrupulous, mema
y*2^2+IF64).
On Sat, 13 Aug 2022, John Ference wrote:
Writing and reading integers to memory is non-deterministically in error,
producing variably incorrect results and segfaults:
One example which occurs about 20% of the time is:
y =. 203
pt=. mema y
(y # 0) memw pt,0,y,4
+/ memr pt,0,y,4
140717552857408
NB. or other non-zero integer
Another example, this one which occurs on approximately 75% of runs is:
wr=.{{
l=. y
pt=. mema l
(l # 0) memw pt,0,l,4
+/ memr pt,0,l,4
}}"0
+/ wr i. 1e5
jconsole(81462,0x1145b5e00) malloc: Incorrect checksum for freed object
0x7fb4ff00b200: probably modified after being freed.
Corrupt value: 0x0
jconsole(81462,0x1145b5e00) malloc: *** set a breakpoint in
malloc_error_break to debug
Abort trap: 6
JVERSION
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Beta-e: commercial/2022-07-16T19:27:13
Library: 9.04.03
Platform: Darwin 64
Installer: J904 install
InstallPath: /applications/j904
Contact: www.jsoftware.com
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