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Re: [ptp-dev] debug output question
See section 24.4.2 in the gdb manual: http://sourceware.org/gdb/ current/onlinedocs/gdb_25.html#SEC243
The target output stream is only supported for remote targets. A remote target is when you use gdb to debug a remote system using gdbserver. For normal uses of gdb, the target output stream doesn't work, which is why we have to use pseudo terminals. It would certainly simplify things to be able use target output streams, but I don't think they have any plans to support it. 

Greg


On Oct 2, 2007, at 2:25 PM, Feiyi Wang wrote:


Greg -

 ... well, I didn't think, I just jump onto it.

 thanks for the info, I will take a closer look at it.
A unrelated question on GDB/MI interface: suppose the target program has a output stream, denoted by @, but as the following interaction shows, "res = 6" stdio from sample program doesn't have @ prefix ... why? 

(gdb)
-exec-continue
^running
(gdb)
res = 6
*stopped,reason="exited-normally"
(gdb)
I also tried MI API to see if I get anything through target callback, and again, nothing comes out of it ... am I missing something here? 

void
target_callback(char *str)
{
	printf("target> %s\n", str);
}

int main()
   sess = MISessionNew();
   if (MISessionStartLocal(sess, "/home/fwang2/gdb/test") < 0) {
		fprintf(stderr, "%s", MIGetErrorStr());
		return 1;
   }

    MISessionRegisterTargetCallback(sess, target_callback);

    cmd = MICommandNew("run", MIResultRecordDONE);	
    MICommandRegisterCallback(cmd, cmd_callback, sess);
    sendcmd_wait(sess, cmd);
...




Greg Watson wrote:

Sorry, too much happening all at once....
You thought this was going to be easy, right?
1. Take a look at line 151 of org.eclipse.ptp.debug.sdm/src/mi/ MISession.c. The -tty argument tells gdb to forward I/O from the program being debugged to the device, in this case /dev/null. You'll need to set up a pseudo terminal and forward the I/O to this instead. Pseudo terminals come in pairs: a master and a slave. Whatever is sent to the master can be read from the slave and vice versa. So you will need to change MISession.c do the following: 
a) Create a pseudo terminal pair.
b) Open the master save the file descriptor. You'll probably want to save it in the MISession structure. c) Pass the slave side of the pseudo terminal to gdb using the - tty argument. d) Modify MISessionProgress() so that it checks this file descriptor and reads from it if there is anything available. e) If you do read something, create an MITargetStreamOutput record using NewMITargetStreamOutput() and add the output to this, then call DoOOBStreamCallbacks() to send the record. f) For the moment, I suggest modifying AsyncCallback in gdbmi_backend.c to check for this event and just print the output to stdout (see AsyncStop for an example of how to check the event type). This *should* get picked up by ORTE and forwarded back to Eclipse. We can work out how to do it properly later. Note: there are at least two ways to create psuedo terminals. The BSD way and the SYSV way. I think Linux supports both. See the wikipedia entry for a description. I should also be able to dig up some sample code if you'd like. 2) No. You can attach gdb to the running process, but it's tricky to know which one. I usually just run the whole SDM on my local machine and observe stdout. 
Let me know if you need more info.
Greg
On Oct 2, 2007, at 11:28 AM, Feiyi Wang wrote:
On my 2nd question, both orte proxy and sdm can be attached by having appropriate debug configuration. However, how gdb/mi layer handle program stdio is not clear to me yet - any help? 

Feiyi

Feiyi Wang wrote:

Greg -
I have made changes to debug_app_job_state_callback to register IO forwarding callback, but I didn't see output being sent back to the front. So the next step of investigation would be to check if the backend (gdb/mi) is send the message back if I understand this correct. Two questions: (1) can you provide any pointers on where I should be looking at (2) is there any way I could set up eclipse debugger to hook into orte proxy and sdm process? 
Thanks
Feiyi
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