Hernan I imagine that valgrind in a "assembler interpreter." It does not blindly execute the next instructions. May be put trap everywhere and I do not think that we can do the same but I'm curious to read the answer about this one. On Sun, Oct 8, 2017 at 10:00 AM, Hernán Morales Durand <hernan.morales@gmail.com> wrote:
Hi Esteban
2017-10-07 5:51 GMT-03:00 Esteban Lorenzano <estebanlm@gmail.com>:
On 7 Oct 2017, at 00:11, Hernán Morales Durand <hernan.morales@gmail.com> wrote:
2017-10-06 2:39 GMT-03:00 Sven Van Caekenberghe <sven@stfx.eu>:
On 6 Oct 2017, at 05:34, Hernán Morales Durand <hernan.morales@gmail.com> wrote:
Hi Nicolas
2017-10-05 16:04 GMT-03:00 Nicolas Cellier <nicolas.cellier.aka.nice@gmail.com>:
2017-10-05 15:42 GMT+02:00 Hernán Morales Durand <hernan.morales@gmail.com>:
I tried, now I get an exception "Use ExternalAddress instead!"
I guess the message means Use ExternalAddres in the "out" parameter. But replacing byte with ExternalAddress also crashes the VM (crash.dmp attached).
2017-10-05 10:03 GMT-03:00 Esteban Lorenzano <estebanlm@gmail.com>:
On 5 Oct 2017, at 14:55, Hernán Morales Durand <hernan.morales@gmail.com> wrote:
Forgot to comment that Nacl worked in Pharo 5.
yes but that was with NB and there are some minimum differences. I do not have the library and I lack the time to try more, but seems to me that here:
apiCryptoHashSha512Output: outByteArray input: inByteArray inputLength: inByteArrayLength
^ self ffiCall: #(long crypto_hash_sha512_ref (byte * outByteArray, byte * inByteArray, ulonglong * inByteArrayLength)) module: 'libsodiumâ.
instead "byte * outByteArrayâ, you want "byte **outByteArrayâ
can you try?
Esteban
Hmm no, internet reference says:
extern int crypto_hash_sha512_ref(unsigned char *,const unsigned char *,unsigned long long);
The error is rather that you pass the address of length rather than the length... So you pass an erroneous length that may lead to a segfault...
Yes, that extra * was the error indeed. Thank you Nicolas.
I do not know the VM internals, however I wonder if it is understandable to expect a VM crash for a typo like this? Maybe it is too difficult to catch in the VM side?
Just asking, not criticizing anyone's work.
Of course that is normal. This is C code, any error has the potential to crash your program. In C there are no runtime safe guards.
There is a reason why we like/use Pharo.
However there are a couple of lightweight libraries which claim to provide exceptions for C: https://github.com/guillermocalvo/exceptions4c or this one https://github.com/psevon/exceptions-and-raii-in-c
I wonder if something like that could be used in UFFI
Nothing in C *ever* will save you from accessing bad memory blocks. And yes, it will always crash your program.
Let me see if I get this right.
If there is nothing to prevent accessing bad memory blocks, assuming accessing or executing invalid memory, then how the memory debuggers like mpatrol or valgrind, do their work? Just a rethoric question to make a point, please keep reading...
Memory debuggers don't prevent segmentation violation of the debuggee, but they don't crash either. I know they slow down application, but it wouldn't be preferable to gracefully recover from crashes during coding time? My (maybe crazy) idea was while coding sensitive parts (like using UFFI) one can use a "debugger vm", and use the "normal vm" when safer.
So I think we are talking about different things here. I don't want to save "bad memory block" errors nor dream about bullet proof VM, but if we know the bullet then let's use a nice bulletproof vest :)
What do you think about having some self-healing feedback loop to "hide" the crash? like the described in https://link.springer.com/article/10.1007/s00607-010-0107-y
In general, how the VM developers view the resilient systems approach? Are they too far away to get it right given the current VM complexity?
those links you point are exception mechanisms, a set of tools to easy the catch of programming exceptions. But, if you try to read a chunk of memory in, say 0x8000 and the data/function that should be there is now garbage, youâre screw.
as Sven pointed, thatâs why we use higher level languages, with GC and all that.
Thank you for the clarifications BTW
Hernán
Esteban
Hernán
Cheers,
Hernán
2017-10-05 3:23 GMT-03:00 Esteban Lorenzano <estebanlm@gmail.com>:
H Hernani,
Most probably is a problem in the library and not UFFI, but I could not know without a crash report.
Esteban
On 5 Oct 2017, at 06:00, Hernán Morales Durand <hernan.morales@gmail.com> wrote:
Hi,
I ported Nacl (a libsodium wrapper) from the old FFI apicall: format to use the UFFI ffiCall:, but there should be something terribly wrong because is crashing the VM, in both Windows 8.1 and Linux.
How to reproduce in Pharo 6.1
Metacello new smalltalkhubUser: 'tonyg' project: 'Crypto-Nacl'; configuration: 'Nacl'; version: #development; load.
(Nacl hashString: 'The quick brown fox jumps over the lazy dog') hex
This one does deserve a bug entry?
Cheers,
Hernán