doc,test: mem protection must be observed in ffi #5664

Job	Run time
Build slim tarball	2m 15s
x86_64-darwin: with shared libraries	9m 54s
aarch64-darwin: with shared libraries	9m 48s
x86_64-linux: with shared libraries	9m 47s
aarch64-linux: with shared libraries	9m 45s
	41m 29s

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