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| strange C behaviour |
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Message
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| HenriqueS |
 Posted: Thu Sep 13, 2007 12:58 pm Post subject: strange C behaviour |
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Master
Joined: 22 Sep 2006
Posts: 235
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Sorry to "bug" about C programming here, but debuging a mq exit is a damn task to do since you cannot do step-by-step debugging...
any good explanation why this does not run?
| Code: |
//setting a message user id...
MQCHAR12 userid;
memset (userid, '\0', 12);
strcpy(userid, "USER");
strncpy(pMQXQH->MsgDesc.UserIdentifier, userid, 12); //crashes here
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I tried replacing "12" with:
a) "sizeof(pMQXQH->MsgDesc.UserIdentifier)"
b) MQ_USER_ID_LENGTH
And it still crashes...strange enough I´ve got an example in the net almost equal:
| Code: |
MQCHAR12 MyMQMD_UserIdentifier ;
memset ( MyMQMD_UserIdentifier, '\0', sizeof(MyMQMD_UserIdentifier) ) ;
strncpy ( MyMQMD_UserIdentifier, pMsgData, LngMsg2Delete ) ;
strncpy ( pMQXQHptr -> MsgDesc.UserIdentifier,
MyMQMD_UserIdentifier,
sizeof(pMQXQHptr -> MsgDesc.UserIdentifier) ) ;
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Any idea? Actualy in the very beginning my code was simple as
| Code: |
strncpy(pMQXQH->MsgDesc.UserIdentifier, "USERxxxxxxxx", 12); but it chrashed also (x=spaces).
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_________________
HenriqueS
Certified Websphere MQ 6.0 System Administrator |
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| HenriqueS |
| Posted: Thu Sep 13, 2007 2:05 pm Post subject: |
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Master
Joined: 22 Sep 2006
Posts: 235
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Forget about it folks, there was no message flowing in the channel and the function was being called anyway with invalid data on the pMQXQH structure...
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HenriqueS
Certified Websphere MQ 6.0 System Administrator |
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| jefflowrey |
| Posted: Thu Sep 13, 2007 2:08 pm Post subject: |
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Grand Poobah
Joined: 16 Oct 2002
Posts: 19981
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| HenriqueS wrote: |
| Forget about it folks, there was no message flowing in the channel and the function was being called anyway with invalid data on the pMQXQH structure... |
Exits are an advanced topic for a reason..  I know I've never been brave enough to try to write one.
It probably wasn't "invalid" data.
It might be "undocumented" data... 
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I am *not* the model of the modern major general. |
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| David.Partridge |
| Posted: Wed Sep 19, 2007 12:06 am Post subject: |
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Master
Joined: 28 Jun 2001
Posts: 249
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You say you can't use a debugger on MQ exits - actually you can - at least under Windows using JIT debugging.
You put typically a divide by zero at the entry point of the exit (using a static variable to hold the zero). When you hit the divide by zero, VC++ gets control, and you change the static variable to be none zero), set your breakpoints and off you go.
I've heard suggestions that it's also possible to get VC++ to set up breakpoints on a DLL that WILL be loaded in the future, but never worked out how to get that working.
Dave |
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