> On 09 Jan 2016, at 05:15, Ben Coman <b...@openinworld.com> wrote:
>
> On Sat, Jan 9, 2016 at 7:12 AM, Mariano Martinez Peck
> <marianop...@gmail.com <mailto:marianop...@gmail.com>> wrote:
>>
>> On Jan 8, 2016 4:13 PM, "Ben Coman" <b...@openinworld.com> wrote:
>>>
>>> On Sat, Jan 9, 2016 at 2:04 AM, Mariano Martinez Peck
>>> <marianop...@gmail.com> wrote:
>>>> Hi guys,
>>>>
>>>> I wonder if someone could give me a hand to find out why a FFI calling I
>>>> am
>>>> doing is crashing. In OSX it works correct but I am testing in CentOS
>>>> and it
>>>> fails. I wonder if it also crashes in other Linuxes too.
>>>
>>> I only had enough time to run it a few time so you know it also
>>> crashes in Debian Jessie 32-bit. There were no debug logs. I got
>>> these sorts of messages...
>>>
>>
>> Thanks!
>>
>>> *** Error in `/home/ben/tst/pharo-vm/pharo': free(): invalid next size
>>> (fast): 0x08841a70 ***
>>>
>>> pharo: malloc.c:3695: _int_malloc: Assertion `(unsigned long) (size)
>>>> = (unsigned long) (nb)' failed.
>>> *** Error in `/home/ben/tst/pharo-vm/pharo': malloc(): memory
>>> corruption: 0x0984c1e0 ***
>>>
>>>
>>> Searching github for "posix_spawn_file_actions_init "
>>> (https://git.io/vuSPL)
>>> I see a lot a function definitions of the form...
>>> int posix_spawn_file_actions_init(posix_spawn_file_actions_t *fa)
>>> {
>>> fa->__actions = 0;
>>> return 0;
>>> }
>>>
>>> ...so it seems you need to first allocate the space for the struct and
>>> then pass the address of that.
>>
>> I thought the same. But I also read in glibc that that the init and destroy
>> would free and alloc exactly so that you don't have to do it.
>>
>> In fact, the structure is known to be opaque. I cannot rely in what I see in
>> internet since each os may have a different.
if it is opaque, they do not provide a function to create one?
>>
>> And I cant get the size of it from ffi so I cannot allocate accurately. I
>> think I am screw. I don't want to go to plugin side grrr ..
but you can map it and you will get the size.
or you can hardcode it (not so bad, if done in the appropriate place), if is
opaque, you do not need to map the structure, just know the size and allocate
that.
Esteban
>>
>> And osx does work.
>>
>> I think I will try against glibc rather than libc.
>>
>> Another idea?
>>
>>> {
>>> int __allocated;
>>> int __used;
>>> struct __spawn_action *__actions;
>>> int __pad[16];
>>> } posix_spawn_file_actions_t;
>>> // http://linux.die.net/include/spawn.h
>>>
>>
>> But that's opaque right? I cannot rely on that
>
> Your ExternalAddress use only allocates 4 bytes for the pointer. You
> need to also allocate the space for the structure. I guess these may
> need separate ExternalXXX objects, but just as hack experiment I find
> below that n:=68 crashes and n:=69 its fine.
>
> | posixSpawnFileActionsT n |
> n := 68. "n := 69"
> posixSpawnFileActionsT := ExternalAddress allocate: n.
> OSSUnixSubprocess new primitivePosixSpawnFileActionsInit:
> posixSpawnFileActionsT.
> posixSpawnFileActionsT free.
>
>
> In trying to understand this I found an interesting article...
> http://www.catb.org/esr/structure-packing/
> <http://www.catb.org/esr/structure-packing/>
> What I don't know is for a 32-bit OS on a 64-bit machine, is my
> pointer 4 or 8 bytes?
> Assuming 4 I derive the structure size for my 32-bit system is...
> 4 int __allocated;
> 4 int __used;
> 4 struct __spawn_action *__actions;
> 64 int __pad[16];
> 76 posix_spawn_file_actions_t;
>
> 76 - 68 = 8 is an interesting round number, but I can't quite reason it out.
>
> With FFI how to you allocate some external memory and then get a
> pointer to it to pass to primitivePosixSpawnFileActionsInit ?
>
> cheers -ben
>
>>>> I am using latest Pharo 5.0 with Spur. To reproduce:
>>>>
>>>> 1) Get latest Pharo 5.0 and Spur via:
>>>> wget -O- get.pharo.org/alpha+vm | bash
>>>>
>>>> 2) Inside Pharo, load my prototype tool:
>>>>
>>>> Gofer it
>>>> package: 'OSSubprocess';
>>>> url: 'http://smalltalkhub.com/mc/marianopeck/OSSubprocess/main';
>>>> load.
>>>>
>>>> 3) This is the code I am executing and it's crashing:
>>>>
>>>> | posixSpawnFileActionsT | posixSpawnFileActionsT := ExternalAddress
>>>> allocate: 4. OSSUnixSubprocess new primitivePosixSpawnFileActionsInit:
>>>> posixSpawnFileActionsT. posixSpawnFileActionsT free.
>>>> 4) The primitive is as simple as:
>>>>
>>>> primitivePosixSpawnFileActionsInit: aPosixSpawnFileActionsT
>>>> ^ self ffiCall: #( int posix_spawn_file_actions_init(void*
>>>> aPosixSpawnFileActionsT) ) module: LibC
>>>>
>>>> I have no idea what I am doing wrong. And again, this works on OSX. The
>>>> function I am calling is: int
>>>> posix_spawn_file_actions_init(posix_spawn_file_actions_t *file_actions);
>>>> as
>>>> you can read in [1]
>>>>
>>>> Below is the stacktrace I get the Linux terminal.
>>>>
>>>> Any hint is greatly appreciated.
>>>>
>>>> Thanks,
>>>>
>>>>
>>>> [1]
>>>>
>>>> http://pubs.opengroup.org/onlinepubs/9699919799/functions/posix_spawn_file_actions_destroy.html
