Hi, I have a class that calls RAND_bytes in libcrypto and I am (mis-?)using NativeBoost for that. The function appears to work in general and I can make 1000000 calls in a row. I am now invoking (RAND bytes: 4) asInteger from within and then get crashes if I insert enough (10000) objects. Iâm using a Pharo3 image with todays Pharo-vm-mac-latest and it is easily reproducible. I am not sure if that is before or after the C code has been called but the frame just looks invalid (hence invalid). I had a breakpoint in the initial call to RAND_bytes and looked at the âtrampolineâ, at the time it is crashing the frame is a different one and the original is gone (disassembles to something different) . Am I using NativeBoost correctly here? Do you have any hints? Is the code moving or being garbage collected? Is there an easy way I could proof the theory? kind regards holger Details * thread #1: tid = 0x120dae, 0x21a70140, queue = 'com.apple.main-thread', stop reason = signal SIGILL frame #0: 0x21a70140 -> 0x21a70140: negl %esp 0x21a70142: addl -0xc(%ebp), %esp 0x21a70145: movl 0xada30, %eax 0x21a7014b: movl (%eax), %eax (lldb) register read General Purpose Registers: eax = 0x21a70110 ebx = 0x000000e8 ecx = 0x00000002 edx = 0x0000000f edi = 0x21a7010c esi = 0x21a70131 ebp = 0xbffacb38 esp = 0x00000008 ss = 0x00000023 eflags = 0x00000202 eip = 0x21a70140 cs = 0x0000001b ds = 0x00000023 es = 0x00000023 fs = 0x00000000 gs = 0x0000000f (lldb) bt * thread #1: tid = 0x120dae, 0x21a70140, queue = 'com.apple.main-thread', stop reason = signal SIGILL * frame #0: 0x21a70140 frame #1: 0x0009827b Pharo`primitiveNativeCall + 107 frame #2: 0x1f400780 (lldb) di -f -> 0x21a70140: negl %esp 0x21a70142: addl -0xc(%ebp), %esp 0x21a70145: movl 0xada30, %eax 0x21a7014b: movl (%eax), %eax 0x21a7014d: movl %esp, -0x10(%ebp) 0x21a70150: subl $0x4, %esp 0x21a70153: andl $0xf, %esp 0x21a70156: negl %esp 0x21a70158: addl -0x10(%ebp), %esp 0x21a7015b: pushl %eax Object subclass: #RAND instanceVariableNames: '' classVariableNames: '' poolDictionaries: '' category: 'Hack'! "-- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- "! RAND class instanceVariableNames: ''! !RAND class methodsFor: 'as yet unclassified' stamp: 'HolgerHansPeterFreyther 7/23/2015 11:49'! intRand: aByteArray size: aSize <primitive: 'primitiveNativeCall' module: 'NativeBoostPlugin'> ^self nbCall: #(int RAND_bytes(byte* aByteArray, int aSize)) module: 'crypto'.! ! !RAND class methodsFor: 'as yet unclassified' stamp: 'HolgerHansPeterFreyther 7/23/2015 11:48'! rand: numberOfBytes | rand | rand := ByteArray new: numberOfBytes. ^(self intRand: rand size: rand size) = 1 ifTrue: [ rand ] ifFalse: [ nil ]! !