I have tracked things down to line 826 in ./jabberd/mio.c (indicated with <===):
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log_debug(ZONE,"mio while loop top");
/* if we are closing down, exit the loop */
if(mio__data->shutdown == 1 && mio__data->master__list == NULL)
break;/* wait for a socket event */
FD_SET(mio__data->zzz[0],&rfds); /* include our wakeup socket */
if(bcast > 0)
FD_SET(bcast,&rfds); /* optionally include our announcements socket
*/
retval = pth_select(maxfd+1, &rfds, &wfds, NULL, NULL); <===
/* if retval is -1, fd sets are undefined across all platforms */
log_debug(ZONE,"mio while loop, working"); ____________________________________________________________
!!!!!
Apparently this call to pth_select() is making Jabberd go BOOM! right on startup.
!!!!!
(Verified this by adding a few more log_debug() lines just before and after the offending call, and sure enough, got up to but not past pth_select()).
Did some Googling and best I could find was the following thread:
http://www.mail-archive.com/[EMAIL PROTECTED]/msg00052.html
which would seem to indicate that possibly enough data is being pushed onto the run-time stack to cause the "STACK OVERFLOW". Not sure why simply enabling debug mode would do this, as all it does is throw out statements (and why does this happen under Cygwin but apparently not under Linux/etc.?).
As written in discussion thread listed above: ________________________________________ There are only one good reason I can think of which cause the stack overflow in such a "simple thread": Some of your functions or functions inside some other libraries (libc, etc.) use large variables on the stack. In C, every variable not declared "static" in a function is per default allocated from the run-time stack. So, if you have a simple "char buf[SIZE]" somewhere and SIZE is a few KB in size, this noticably fills the stack of the thread while the function's scope is active. ________________________________________
Looked at the code for debug_log() in ./jabberd/log.c, which is basically what's called. log_debug is just a macro that resolves to a conditional check to see if debug_flag is set, in which case run debug_log() is called (see ./jabberd/jabberd.h lines 109-113).
Only thing I see is the declarations at the beginning of debug_log():
va_list ap;
char message[MAX_LOG_SIZE];
char *pos, c = '\0';
int offset;which might push a good bit of data on the stack depending on what the size of the va_list type is and the value of MAX_LOG_SIZE (which is 1024 as seen on line 105 in jabberd.h). But if that's the cause, I don't think I'd be seeing the last debug message ("mio while loop top") as the program should be bombing out as the code enters debug_log(). And considering this function is called, entered, run, and returned, any values it pushed on the stack are popped before continuing.
The only other thing I see that might affect the run-time stack are the calls to FD_SET(), which I'm not quite sure how they resolve. All caps indicates a #define, but did a grep through the code and found nothing. Looked at the GNU Pth docs, and nothing there except references to lower-case 'fd_set' var type. Googling makes me think this is some kind of Unix standard connected with the select() function (which appears to be superceded/replaced by GNU Pth where it's used), so not quite sure how one plays with the other. But maybe FD_SET under Cygwin pushes more data onto the stack than it does under *nix? But does turning on debug output really cause this? Not sure they're connected when I look at the code.
Guess at this point I'm kind of at a loss. Looks like serious reading time to try and get up to speed on all this. But if anyone out there-- unlike me out on the fringes--has intimate knowledge of this code or just the whole pthread vs. GNU Pth function calls, I'd love to get some insight. Thanks in advance for reading this far and for any help you can provide.
____________________________________________________________ ACCESSING VARIABLES FROM OUTSIDE COMPILED MODULE UNDER CYGWIN AND MU-Conference
After noting lines 109-113 in ./jabberd/jabberd.h, it occurred to me that jabberd.exe is compiled slightly differently under Cygwin than it is under *nix. *nix version just checks debug_flag var directly (which is declared in ./jabberd/log.c), whereas Cygwin version calls a trivial function to do same. (NOTE: Did a grep on all the jabberd code, and this is the ONLY reference to __CYGWIN__ I can find in the entire source tree!! So is this really the only difference in code now?)
Not sure why that's necessary, but removing this conditional, using just the *nix version of the #define, and re-compiling gave a few hiccups. Had to add a line to the Makefile to add one more export variable for doing the non-*nix build of export lib. But even then things weren't 100% right, as running jabberd.exe gave issues.
I suspect this all ties in with the way dynamic libraries can hook back into variables exported from executables in *nix but trying to do something similar under Cygwin gives all kinds of headaches (see post from 6Nov2003 for more info). And this simple "wrapper" function might be a trick, possibly because under Cygwin functions can be exported but variables cannot? (That's a question, not a statement.) I have no clue. So I've left this alone for now.
But this might explain why MU-Conference v0.52 blows up on me as well, whereas v0.3 does not. MU-C v0.52 appears to try and connect back into a variable deliver__flag, which is defined in ./jabberd/deliver.c and compiled into jabberd.exe. I added this variable to the export list via the Makefile, which allows MU-C v0.52 to compile/link against ./jabberd/jabberd.a just fine, but MU-C still blows sky high when a room is created. However, MU-C v0.3 suffers none of these issues, and compiles fine without that entry, implying MU-C v0.3 does NOT try to look at deliver__flag. Anyway, just more observations.
Frank Seesink wrote: ...
Ok, I admit it. I'm kind of on a mission. At this point Jabberd 1.4.3CVS compiles/links/runs the same under Cygwin as it does on other *nix platforms, with the one exception of running in debug mode (using the -D switch).
So let me ask this, as I'm just starting to dig into the source code itself. Can anyone steer me in the right direction as to why, whenever I attempt to fire up Jabberd in debug mode, I see the following:
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$ ./jabberd/jabberd.exe -D
Sat Nov 8 18:44:11 2003 mio.c:787 MIO is starting up
Sat Nov 8 18:44:11 2003 mio.c:816 mio while loop top
**Pth** STACK OVERFLOW: thread pid_t=0xa040750, name="unknown"
Segmentation fault
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This happens regardless of whether I have configured/built jabberd with (--enable-ssl) or without SSL support. So I've ruled that out at least. It fails with the generic jabber.xml config. Basically, I have not been able to get Jabberd to fire up if I use the -D switch.
The actual pid_t number may vary (haven't been paying enough attention to notice if it changes or if there's a pattern to be honest), but the sequence of messages is always the same. Jabberd starts and dies in the blink of an eye.
However, simply NOT running in debug mode avoids ALL this, and I've had a Jabber server running for weeks at a time in production (granted, low user load, but still), usually only restarting when I reboot the Windows XP Pro box it's running on.
Has anyone else experienced this kind of behavior on any other platform? Any insight into where to look? I realize running Cygwin under Windows, I'm working in a cludged environment at best. But figured it best to ask you good folks if you've ever seen this before, as you might save me a great deal of time in finding the source of the problem...even if the end result is just "It's a limitation of Cygwin/Windows. Suck it up." :-)
In the meantime, the hunt continues...
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