modbus_set_response_timeout cause segmentation fault

[Antoine Croteau]

Hello people,

 

 

 

I'm currently coding a C++ program running on a stripped down Linux. I'm using Buildroot to compile the libraries.

 

 

 

I am using Libmodbus version 3.1.2. To get that version working, I had to modify Buildroot's Libmodbus package with  "LIBMODBUS_VERSION = 3.1.2", "LIBMODBUS_LIBTOOL_PATCH= NO" and remake.

 

 

 

I can Read/Write in TCP/UDP, everything works fine, except when I try to do a "modbus_set_response_timeout".

 

When I call it, I get a segmentation fault. I have no idea what can cause this. Even the "modbus_get_response_timeout" works. I just tried modbus_set_byte_timeout and it cause a seg fault too...

 

 

 

Sorry I don't have much more information, but it's pretty straightforward.

 

 

 

Anyone have any idea? Maybe I should just go back to 3.0.6.

 

 

 

Thanks a lot, Antoine

[Stéphane Raimbault]

Could you paste the code you use to set the timeout?

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[Antoine Croteau]

mModbusContext = modbus_new_tcp_pi(mIPAddr.c_str(), mIPPort.c_str());

if (mModbusContext == nullptr)

{

   mError = errno;

   return false;

}

else

{

    modbus_set_response_timeout(mModbusContext, 0, 200000);

}

if (modbus_connect(mModbusContext) == -1)

{

   mError = errno;

   modbus_free(mModbusContext);

   mModbusContext = nullptr;

   return false;

}

return true;

Thank you for your time and the fast answer.

[Antoine Croteau]

When I run my program with Valgrind, I get the following on the modbus_set_response_timeout call :

==1430== Invalid read of size 4

==1430==    at 0x4C234E8: modbus_set_response_timeout (in /usr/lib/libmodbus.so.5.0.4)

==1430==  Address 0x0 is not stack'd, malloc'd or (recently) free'd

Valgrind doesnt seem very explicit. I don't know if this will help.

[Stéphane Raimbault]

I think you don't use the right version of the library.

/usr/lib/libmodbus.so.5.0.4 must be v3.0.X where as the API you use is for v3.1.X and above.

--

[Antoine Croteau]

Ooohh, that's it. I forgot to copy the .so compiled with Buildroot in my program's lib folder..

It works great now. Thanks a lot for the library and answering my question.

Have a good day,

Antoine

[Muhammad U. Anwar]

Hi,

I am having the same problem as @Antoine Croteau. Can anyone please help me what is the described solution in little bit more detail. 

Thanks, 

[zouro...@gmail.com]

Hi Stephane,

The library is really great! I just have a problem with the set_response_timeout function where it causes a segmentation fault. Would you please advise me on this?

Thanks.