doc,test: mem protection must be observed in ffi #5691

Job	Run time
Build slim tarball	2m 21s
x86_64-darwin: with shared libraries	33m 40s
x86_64-linux: with shared libraries	22m 41s
aarch64-darwin: with shared libraries	23m 30s
aarch64-linux: with shared libraries	18m 43s
	1h 40m 55s

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