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Date: Thu, 14 Jan 2010 19:38:21 +0100
From: Simon Boulay <simon.boulay@domain.hid>
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Subject: Re: [Xenomai-help] problem with libanalogy
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To: xenomai@xenomai.org

On 01/14/2010 06:07 PM, Alessio Margan @ IIT wrote:
> Simon Boulay wrote:
>> Hi,
>>
>> On 01/13/2010 06:19 PM, Alessio Margan @ IIT wrote:
>>
>>> Hi,
>>>
>>> I've got "Segmentation fault" from libanalogy.so.1
>>> Here is part of code ...
>>>
>>> int s526Analogy::Open()
>>> {
>>> int ret = 0;
>>> boardIsOpen = false;
>>>
>>> ret = a4l_open(&dsc, dev_name);
>>> if (ret<   0) {
>>> fprintf(stderr, "s526Analogy::Open : a4l_open %s failed (ret=%d)\n",
>>> dev_name, ret);
>>> return boardIsOpen;
>>> }
>>>
>>> fprintf(stderr, "s526Analogy::Open : name : %s\nsubd %d\nrd subd %d\nwr
>>> subd %d\nfd %d\nmagic %x\nsize %d\n",
>>> dsc.board_name,
>>> dsc.nb_subd,
>>> dsc.idx_read_subd,
>>> dsc.idx_write_subd,
>>> dsc.fd,
>>> dsc.magic,
>>> dsc.sbsize);
>>>
>>> dsc.sbdata = malloc(dsc.sbsize);
>>> if (dsc.sbdata == NULL) {
>>> ret = -ENOMEM;
>>> fprintf(stderr, "s526Analogy::Open : info buffer allocation failed\n");
>>> return boardIsOpen;
>>> }
>>> ret = a4l_fill_desc(&dsc);
>>> if (ret<   0) {
>>> fprintf(stderr, "s526Analogy::Open : a4l_fill_desc failed (ret=%d)\n", ret);
>>> return boardIsOpen;
>>> }
>>>
>>> boardIsOpen = true;
>>> printf("Open %s\n", dev_name);
>>>
>>> return boardIsOpen;
>>> }
>>>
>>> and here is the back trace from gdb ....
>>>
>>> s526Analogy::Open : name : analogy_s526
>>> subd 4
>>> rd subd 1
>>> wr subd 2
>>> fd 0
>>> magic 1234abcd
>>> size 1560
>>>
>>> Program received signal SIGSEGV, Segmentation fault.
>>> [Switching to Thread 0xb7151990 (LWP 6138)]
>>> 0xb773a64a in a4l_sys_desc () from /usr/xenomai/lib/libanalogy.so.1
>>> Current language: auto; currently asm
>>> (gdb) bt
>>> #0 0xb773a64a in a4l_sys_desc () from /usr/xenomai/lib/libanalogy.so.1
>>> #1 0xb773a748 in a4l_fill_desc () from /usr/xenomai/lib/libanalogy.so.1
>>> #2 0x0804ebb2 in s526Analogy::Open (this=0x805e560) at s526Analogy.cpp:55
>>> #3 0x0804f8c6 in configure_board () at s526Main.cpp:95
>>> #4 0x0804f96a in main () at s526Main.cpp:115
>>> (gdb)
>>>
>>> dmesg give me ...
>>>
>>> app[6454]: segfault at 40 ip b772964a sp bfd372d0 error 4 in
>>> libanalogy.so.1.0.0[b7728000+3000]
>>>
>>>
>>> Yesterday I pull xenomai-head to get last commits, before I've run the
>>> application without this segfault.
>>>
>> I can't reproduce your problem.
>> Does the same thing happen with the following command:
>> insn_read -v -d analogy0?
>>
>> Simon.
>>
>>   >
>>
>>> TIA
>>>
>>> Alessio
>>>
>>>
>>>
> Thanks,
>
> insn_read and insn_write works fine, seems that reset the buffer wiht
> zeroes works ...
>
> dsc.sbdata = malloc(dsc.sbsize);
> bzero(dsc.sbdata, dsc.sbsize);
> or
> dsc.sbdata = calloc(dsc.sbsize,1);
>
> without I got segfaults.
>
> Any idea ?
It seems more likely that the problem comes from the application this 
time but I can't confirm without repoducing the problem. You can send me 
more code if you will. I don't see the scope of the dsc variable for 
example.
For my tests, I simply replaced S526Analogy::Open() by a main function 
and add this at the begining:
const char *dev_name = "analogy0";
bool boardIsOpen = false;
a4l_desc_t dsc = { .sbdata = NULL };

Does this work for you?

Simon.