modbus.c:164: error: `MSG_DONTWAIT' undeclared

[Yishin Li]

The trunk branch can not be build on Cygwin.

Error message:
libtool: compile: gcc -DHAVE_CONFIG_H -I. -I.. -g -O2 -MT modbus.lo -MD -MP -MF .deps/modbus.Tpo -c modbus.c -DDLL_EXPORT -DPIC -o .libs/modbus.o
modbus.c: In function `modbus_flush':
modbus.c:164: error: `MSG_DONTWAIT' undeclared (first use in this function)

Reason:
There's no MSG_DONTWAIT macro defined in /usr/include/cygwin/socket.h

[Stéphane Raimbault (sra)]

Try to replace MSG_DONTWAIT by 0 and add a printf just before
then run the unit test named unit-test-master (you need to run unit-test-slave before).

Try to observe the behaviour when a flush occurs to see if the call to recv() is blocking with your flag.

[Yishin Li (yishin-li)]

The compile process passed after replacing MSG_DONTWAIT by 0.
However, I hit "Bug #333455" while launching unit-test-master.
After workaround it, I got the following error message:

$ ./unit-test-master.exe :
TEST BAD RESPONSE ERROR:
ERROR Quantity not corresponding to the query (3 != 2) (10)
modbus_flush(): before recv()
modbus_flush(): after recv(), ret(2)
modbus_flush(): before recv()

$ ./unit-test-slave.exe :
Waiting for a message...
<00><14><00><00><00><06><FF><03><00><6B><00><02>
[00][14][00][00][00][09][FF][03][06][02][2B][00][00][00][64]
Waiting for a message...
Error in modbus_listen (-19)
Waiting for a message...
Error in modbus_listen (-19)
Waiting for a message...
Error in modbus_listen (-19)

[Yishin Li (yishin-li)]

> Try to observe the behaviour when a flush occurs to see if the call to recv() is blocking with your flag.

You are right; the unit-test-master got blocked by the recv() as there's no more messages coming from the TCP/IP queue. I'm thinking of implementing modbus_flush() with pselect() or ppoll(). Is it reasonable?

Sorry about that I didn't pay too much attention on this issue. Basically because I'm new to modbus, and don't have strong idea about it.

BTW, I am currently evaluating a suitable communication protocol for real-time control through USB interface. I will post my question on the Answer forum later.

-Yishin

[Stéphane Raimbault (sra)]

Could you try the following patch?

[Yishin Li (yishin-li)]

Yes, it works!

Attached is my patch, which remove printf() for select() and check if there's error returned by select().

[Stéphane Raimbault (sra)]

The fix wasn't committed yet

[Yishin Li (yishin-li)]

I'm new to bazaar, and kind of get confused by it @@
I thought I was commit my modification.
Now, I realized that was just committing to my local repository.

The "bzr merge" gave me a lot of conflicts and messages that I don't quiet understand. I'm a CVS/SVN user, and am currently studying the Bazaar User Guide.