On MacOS 10.9 MIDAS will crashes in strlcpy() somewhere inside odb.c. We think this is because strlcpy() 
in MacOS 10.9 was changed to abort() if input and output strings overlap. For overlapping memory one is 
supposed to use memmove(). This is fixed in current midas, for older versions, you can try this patch:

konstantin-olchanskis-macbook:midas olchansk$ git diff
diff --git a/src/odb.c b/src/odb.c
index 1589dfa..762e2ed 100755
--- a/src/odb.c
+++ b/src/odb.c
@@ -6122,7 +6122,10 @@ INT db_paste(HNDLE hDB, HNDLE hKeyRoot, const char *buffer)
                   pc++;
                while ((*pc == ' ' || *pc == ':') && *pc)
                   pc++;
-               strlcpy(data_str, pc, sizeof(data_str));
+
+               //strlcpy(data_str, pc, sizeof(data_str)); // MacOS 10.9 does not permit strlcpy() of overlapping 
strings
+               assert(strlen(pc) < sizeof(data_str)); // "pc" points at a substring inside "data_str"
+               memmove(data_str, pc, strlen(pc)+1);
 
                if (n_data > 1) {
                   data_str[0] = 0;
konstantin-olchanskis-macbook:midas olchansk$ 


As historical reference:

a) MacOS documentation says "behavior is undefined", which is no longer true, the behaviour is KABOOM!
https://developer.apple.com/library/mac/documentation/Darwin/Reference/ManPages/man3/strlcpy.3.h
tml

b) the original strlcpy paper from OpenBSD does not contain the word "overlap" 
http://www.courtesan.com/todd/papers/strlcpy.html

c) the OpenBSD man page says the same as Apple man page (behaviour undefined)
http://www.openbsd.org/cgi-bin/man.cgi?query=strlcpy

d) the linux kernel strlcpy() uses memcpy() and is probably unsafe for overlapping strings
http://lxr.free-electrons.com/source/lib/string.c#L149

e) midas strlcpy() looks to be safe for overlapping strings.

K.O.

Hi,

I run into problems while trying to install Midas on Slackware 14.0. In the past
I have easily installed Midas on many other versions of Slackware. I have a new
computer set up with Slackware 14.0 and I just got the Midas latest version from 
https://bitbucket.org/tmidas/midas

Apparently there is a problem with a shared library which should be on the
system, I think make checks for /usr/include/mysql and then supposes that
libodbc.so should be on disk. I don't know why on my system it is not.

But I was wondering if I have some other problems (configuration problem?)
because I get a very large number of warnings. My last installation of Midas is
like from two years ago but I don't remember getting many warnings. Do I do
something obviously wrong? Here is uname -a output and I attached a file with
the output from make in midas folder (GNU Make 3.82 Built for
x86_64-slackware-linux-gnu). Thanks a lot!

Linux lheppc83 3.2.29 #2 SMP Mon Sep 17 14:19:22 CDT 2012 x86_64 Intel(R)
Xeon(R) CPU           E5520  @ 2.27GHz GenuineIntel GNU/Linux

Seems to me a problem with the ODBC library, so maybe Konstantin can comment.

/Stefan

> I run into problems while trying to install Midas on Slackware 14.0.

Thank you for reporting this. We do not have any slackware computers so we cannot see these message usually.

We use SL/RHEL 5/6 and MacOS for most development, plus we now have an Ubuntu test machine, where I see a 
whole different spew of compiler messages.

Most of the messages are:

a) useless compiler whining:

src/midas.c: In function 'cm_transition2':
src/midas.c:3769:74: warning: variable 'error' set but not used [-Wunused-but-set-variable]

b) an actual error in fal.c:

src/fal.c:131:0: warning: "EQUIPMENT_COMMON_STR" redefined [enabled by default]

c) actual error in fal.c: assignment into string constant is not permitted: char*x="aaa"; x[0]='c'; // core dump

src/fal.c:383:1: warning: deprecated conversion from string constant to 'char*' [-Wwrite-strings]

these are fixed by making sure all such pointers are "const char*" and the corresponding midas functions are 
also "const char*".

d) maybe an error (gcc sometimes gets this one wrong)

./mscb/mscb.c: In function 'int mscb_info(int, short unsigned int, MSCB_INFO*)':
./mscb/mscb.c:1682:8: warning: 'size' may be used uninitialized in this function [-Wuninitialized]
 
> Apparently there is a problem with a shared library which should be on the
> system, I think make checks for /usr/include/mysql and then supposes that
> libodbc.so should be on disk. I don't know why on my system it is not.

g++  -g -O2 -Wall -Wno-strict-aliasing -Wuninitialized -Iinclude -Idrivers -I../mxml -I./mscb -Llinux/lib -
DHAVE_FTPLIB -D_LARGEFILE64_SOURCE -DHAVE_MYSQL -I/usr/include/mysql -DHAVE_ODBC -DHAVE_SQLITE 
-DHAVE_ROOT -pthread -m64 -I/home/exodaq/root_5.35.10/include -DHAVE_ZLIB -DHAVE_MSCB -DOS_LINUX 
-fPIC -Wno-unused-function -o linux/bin/mhttpd linux/lib/mhttpd.o linux/lib/mgd.o linux/lib/mscb.o 
linux/lib/sequencer.o linux/lib/libmidas.a linux/lib/libmidas.a -lodbc -lsqlite3 -lutil -lpthread -lrt -lz -lm
/usr/lib64/gcc/x86_64-slackware-linux/4.7.1/../../../../x86_64-slackware-linux/bin/ld: cannot find -lodbc

The ODBC library is not found (shared .so or static .a).

The Makefile check is for /usr/include/sql.h (usually part of the ODBC package). On the command line above, 
HAVE_ODBC is set, and the rest of MIDAS compiled okey, so the ODBC header files at least are present. But why 
the library is not found?

I do not know how slackware packages this stuff the way they do and I do not have a slackware system to check 
how it should look like, so I cannot suggest anything other than commenting out "HAVE_ODBC := ..." in the 
Makefile.


> But I was wondering if I have some other problems (configuration problem?)
> because I get a very large number of warnings. My last installation of Midas is
> like from two years ago but I don't remember getting many warnings.

There are no "many warnings". Mostly it's just one same warning repeated many times that complains about 
perfectly valid code:

src/midas.c: In function 'cm_transition':
src/midas.c:4388:19: warning: variable 'tr_main' set but not used [-Wunused-but-set-variable]

They complain about code:
 { int i=foo(); ... } // yes, "i" is not used, yes, if you have to keep it if you want to be able to see the return value 
of foo() in gdb.



> Do I do something obviously wrong?

No you. GCC people turned on one more noisy junk warning.

> Thanks a lot!

No idea about your missing ODBC library, I do not even know how to get a package listing on slackware (and 
proud of it).

But if you do know how to get a package listing for your odbc package, please send it here. On RHEL/SL, I would 
do:

rpm -qf /usr/include/sql.h ### find out the name of the package that owns this file
rpm -ql xxx ### list all files in this package

K.O.

> > I run into problems while trying to install Midas on Slackware 14.0.
> 
> b) an actual error in fal.c:
> 
> src/fal.c:131:0: warning: "EQUIPMENT_COMMON_STR" redefined [enabled by default]
> 
> c) actual error in fal.c: assignment into string constant is not permitted: char*x="aaa"; x[0]='c'; // core dump
> 
> src/fal.c:383:1: warning: deprecated conversion from string constant to 'char*' [-Wwrite-strings]
> 
> these are fixed by making sure all such pointers are "const char*" and the corresponding midas functions are 

the warnings in fal.c are now fixed.

K.O.

> > I run into problems while trying to install Midas on Slackware 14.0.
> 
> Thank you for reporting this. We do not have any slackware computers so we cannot see these message usually.
> 
> 
> src/midas.c: In function 'cm_transition2':
> src/midas.c:3769:74: warning: variable 'error' set but not used [-Wunused-but-set-variable]
> 

got around to look at compile messages on ubuntu: in addition to "variable 'error' set but not used" we have these:

warning: ignoring return value of 'ssize_t write(int, const void*, size_t)'
warning: ignoring return value of 'ssize_t read(int, void*, size_t)'
warning: ignoring return value of 'int setuid(__uid_t)'
and a few more of similar

K.O.

> got around to look at compile messages on ubuntu: in addition to "variable 'error' set but not used" we have these:
> 
> warning: ignoring return value of 'ssize_t write(int, const void*, size_t)'
> warning: ignoring return value of 'ssize_t read(int, void*, size_t)'
> warning: ignoring return value of 'int setuid(__uid_t)'
> and a few more of similar

Arghh, now it is getting even more picky. I can understand the "variable xyz set but not used" and I'm willing to remove all the variables. But checking the 
return value from every function? Well, if the disk gets full, our code will silently ignore this for write(), so maybe it's not a bad idea to add a few checks. Also 
for the read(), there could be some problem, where an explicit cm_msg() in case of an error would help.

Hi, Thanks a lot for the response! Yes to search packages and list their content in Slackware it is pretty similar to your illustration. Slackware seems to use iODBC in which case it would link with -liodbc I guess.

root@lheppc83:~# slackpkg file-search sql.h

Looking for sql.h in package list. Please wait... DONE

The list below shows the packages that contains "sql\.h" file.

[ installed ] - libiodbc-3.52.7-x86_64-2

You can search specific packages using "slackpkg search package".

root@lheppc83:~# cat /var/log/packages/libiodbc-3.52.7-x86_64-2
PACKAGE NAME:     libiodbc-3.52.7-x86_64-2
COMPRESSED PACKAGE SIZE:     255.0K
UNCOMPRESSED PACKAGE SIZE:     1.0M
PACKAGE LOCATION: /var/log/mount/slackware64/l/libiodbc-3.52.7-x86_64-2.txz
PACKAGE DESCRIPTION:
libiodbc: libiodbc (Independent Open DataBase Connectivity)
libiodbc:
libiodbc: iODBC is the acronym for Independent Open DataBase Connectivity,
libiodbc: an Open Source platform independent implementation of both the ODBC
libiodbc: and X/Open specifications.  It allows for developing solutions
libiodbc: that are language, platform and database independent.
libiodbc:
libiodbc:
libiodbc:
libiodbc: Homepage: http://iodbc.org/
libiodbc:
FILE LIST:
./
usr/
usr/share/
usr/share/libiodbc/
usr/share/libiodbc/samples/
usr/share/libiodbc/samples/iodbctest.c
usr/share/libiodbc/samples/Makefile
usr/man/
usr/man/man1/
usr/man/man1/iodbc-config.1.gz
usr/man/man1/iodbctestw.1.gz
usr/man/man1/iodbctest.1.gz
usr/man/man1/iodbcadm-gtk.1.gz
usr/bin/
usr/bin/iodbctest
usr/bin/iodbcadm-gtk
usr/bin/iodbctestw
usr/bin/iodbc-config
usr/include/
usr/include/iodbcinst.h
usr/include/sqlext.h
usr/include/iodbcunix.h
usr/include/isqltypes.h
usr/include/sql.h
usr/include/iodbcext.h
usr/include/isql.h
usr/include/odbcinst.h
usr/include/isqlext.h
usr/include/sqlucode.h
usr/include/sqltypes.h
usr/lib64/
usr/lib64/libiodbc.la
usr/lib64/libdrvproxy.so.2.1.19
usr/lib64/libiodbcinst.la
usr/lib64/libiodbcadm.so.2.1.19
usr/lib64/libiodbcinst.so.2.1.19
usr/lib64/libiodbcadm.la
usr/lib64/pkgconfig/
usr/lib64/pkgconfig/libiodbc.pc
usr/lib64/libiodbc.so.2.1.19
usr/lib64/libdrvproxy.la
usr/doc/
usr/doc/libiodbc-3.52.7/
usr/doc/libiodbc-3.52.7/ChangeLog
usr/doc/libiodbc-3.52.7/README
usr/doc/libiodbc-3.52.7/COPYING
usr/doc/libiodbc-3.52.7/AUTHORS
usr/doc/libiodbc-3.52.7/INSTALL
install/
install/doinst.sh
install/slack-desc

# slackpkg file-search sql.h
[ installed ] - libiodbc-3.52.7-x86_64-2
...
# slackpkg search package
...
# cat /var/log/packages/libiodbc-3.52.7-x86_64-2
            usr/include/sql.h
...
            usr/lib64/libiodbc.so.2.1.19
...

Thanks, I am saving the slackpkg commands for future reference. Looks like the immediate problem is 
with the library name: libiodbc instead of libodbc. But the header file sql.h is the same.

I am not sure if it is worth making a generic solution for this: on MacOS, all ODBC functions are now 
obsoleted, to be removed, and since we are stanardized on MySQL anyway, so I think I will rewrite the SQL 
history driver to use the MySQL interface directly. Then all this ODBC extra layering will go away.

K.O.

The warnings with the set but unused variables are real. While John O'Donnell proposed:

==========

somewhere I long the way I found an include file to help remove this kind of message.  try something like:

#include "use.h"
int foo () { return 3; }
int main () {
 { USED int i=foo(); }
 return 0;
}

with -Wall, and you will see the unused messages are gone.

==========

I would rather go and remove the unused variables to clean up the code a bit. Unfortunately my gcc version does 
not yet bark on that. So once I get a new version and I got plenty of spare time (....) I will consider removing all 
these variables.

/Stefan

> #include "use.h"
>  { USED int i=foo(); }

Sounds nifty, but google does not find use.h.

As for unused variables, some can be removed, others not so much, there is some code in there:

int i = blah...
#if 0
if (i=42) printf("wow, we got a 42!\n");
#endif
and
if (0) printf("debug: i=%d\n", i);

(difference is if you remove "i" or otherwise break the disabled debug code, "#if 0" will complain the next time you need that debugging code, "if (0)" will 
complain right away).

Some of this disabled debug code I would rather not remove - so much debug scaffolding I have added, removed, added again, removed again, all in the same 
places that I cannot be bothered with removing it anymore. I "#if 0" it and it stays there until I need it next time. But of course now gcc complains about it.

K.O.

MIDAS "programs" settings include: /programs/xxx/"auto start", "auto restart" and "auto stop". What do 
they do?

"auto start":

if set to "y", the program's "start command" will be unconditionally executed at the beginning of the run 
start transition.

Because there are no checks or tests, the "start command" will be executed even if the program is already 
running. It means that this function cannot be used to start frontend programs - a new copy will be 
started each time, and a previously running copy will be killed.

Also the timing of the program startup and run transition is wrong - in my tests, the program starts too 
late to see the run transition. If the program is a frontend, it will never see the begin-of-run transition.

1st conclusion: "auto start" should be "n" for frontend programs and for any other programs that are 
supposed to be continuously running (mlogger, lazylogger, etc).

2nd conclusion: "auto start" does the same thing as "/programs/execute on start run".

"auto stop":

if set to "y", the program will be stopped after the end of run. (using cm_shutdown).

"auto restart":

this has nothing to do with starting and stopping runs. Instead, it works in conjunction with the alarm 
system and the "program is not running" alarm.

The alarm system periodically calls al_check(). al_check() checks all programs defined under /Programs to 
see if they are running (using cm_exist()). If a program is not running and an alarm is defined, the alarm is 
raised ("program is not running" alarm). If there is a start command and "auto restart" is set to "y", the 
start command is executed.

When using these "auto start" and "auto restart" functions, one needs to be careful about the context 
where the start command will be executed: midas clients may be running from different directories, under 
different user names and on different computers.

In "auto start", the start command is executed from cm_transition. For remote clients, this will happen on 
the remote computer. (against the expectation that the program will be started on the main computer).

In "auto restart", the start command is executed by al_check() which always runs locally (for remote 
clients, it runs inside the mserver). So the started program will always run on the main computer, but 
maybe not in the same directory as when started from the mhttpd "programs -> start" button.

Conclusion:

"programs auto start" : works but has strange interactions and side effects, do not use it.
"programs auto stop" : works, can be used to stop programs at the end of run (but what for?)
"programs auto restart" : works, seems to work correctly, can be used to auto restart mlogger, frontends, 
etc.

K.O.

> "programs auto start" : works but has strange interactions and side effects, do not use it.
> "programs auto stop" : works, can be used to stop programs at the end of run (but what for?)
> "programs auto restart" : works, seems to work correctly, can be used to auto restart mlogger, frontends, 

auto start and auto stop have been requested by PAA loooong time ago. Maybe he remembers if/where this has been used at all. I never used it. So if 
this is the case for others, we can easily change it and won't break anything. Like auto start can be executed before the run transition happens, check 
for a previous version of the program, and only continue when the program is actually running. Should be only a few lines of code. Auto restart is used 
successfully here at PSI, for example for the lazy logger.

/Stefan

A problem existed in midas for some time: when recording long data sets of time (or event) limited runs 
with logger run auto restart set to "yes", the runs will automatically stop and restart as expected, but 
sometimes the run will stop and never restart and beam will be lost until the experiment operator on shift 
wakes up and restarts the run manually.

I have now traced this problem to a race condition inside the mlogger - when a run is being stopped from 
the mlogger, the mlogger run transition handler (tr_stop) triggers an immediate attempt to start the next 
run, without waiting for the run-stop transition to actually complete. If the run-stop transition does not 
finish quickly enough, a safety check in start_the_run() will cause the run restart attempt to silently fail 
without any error message.

This race condition is pretty rare but somehow I managed to replicate it while debugging the 
multithreaded transitions. It is fixed by making mlogger wait until the run-stop transition completes.

https://bitbucket.org/tmidas/midas/commits/b2631fbed5f7b1ec80e8a6c8781ada0baed7702b

K.O.

> A problem existed in midas for some time: when recording long data sets of time (or event) limited runs 
> with logger run auto restart set to "yes", the runs will automatically stop and restart as expected, but 
> sometimes the run will stop and never restart and beam will be lost until the experiment operator on shift 
> wakes up and restarts the run manually.
> 
> I have now traced this problem to a race condition inside the mlogger - when a run is being stopped from 
> the mlogger, the mlogger run transition handler (tr_stop) triggers an immediate attempt to start the next 
> run, without waiting for the run-stop transition to actually complete. If the run-stop transition does not 
> finish quickly enough, a safety check in start_the_run() will cause the run restart attempt to silently fail 
> without any error message.
> 
> This race condition is pretty rare but somehow I managed to replicate it while debugging the 
> multithreaded transitions. It is fixed by making mlogger wait until the run-stop transition completes.
> 
> https://bitbucket.org/tmidas/midas/commits/b2631fbed5f7b1ec80e8a6c8781ada0baed7702b
> 
> K.O.

More generally I kind of consider the mlogger auto restart facility as deprecated. It works in the background and the operator does not have a clue 
what is going on. We use now the sequencer to achieve exactly the same functionality. It just requires a few lines of sequencer code:

LOOP INFINITE 
  TRANSITION start 
  WAIT events, 5000 
  TRANSITION stop 
ENDLOOP 

So the run start is only executed after the runs has been successfully stopped. You can do things in the sequencer like "stop run and sequence 
immediately" or "stop after current run has finished" which are a bit hard to do with the old method. So people should move to the sequencer.

/Stefan

> 
> More generally I kind of consider the mlogger auto restart facility as deprecated. It works in the background and the operator does not have a clue 
> what is going on. We use now the sequencer to achieve exactly the same functionality.
>

Before subruns were available, most experiments at TRIUMF have used the "auto restart" function. Now, I think most of them use subruns,
with the notable exception of PIENU where the analysis framework could not handle subruns. (PIENU is now shutdown and disassembled).

>
> It just requires a few lines of sequencer code:
> 
> LOOP INFINITE 
>   TRANSITION start 
>   WAIT events, 5000 
>   TRANSITION stop 
> ENDLOOP 
> 

Mouse click "auto restart" to "yes" is a little bit simpler than setting up a sequencer file, and it survives a crash of mhttpd.

Does the sequencer survive a crash or a restart of mhttpd?

K.O.

> Does the sequencer survive a crash or a restart of mhttpd?

Yes. Of course runs will not be started/stopped when mhttpd is not running, but when you restart it gracefully continues where it stopped, since all variables such as event count or current line number of 
the sequence are store in the ODB.

/Stefan

The following code found in mhttpd does not work on MacOS (BSD UNIX).

On Linux, the do-loop will finish after 2 seconds as expected. On MacOS (and other BSD systems), it will 
loop forever.

The cause is the MIDAS watchdog alarm() signal that fires every 1 second and always interrupts the 2 
second sleep of select(). The Linux select() updates it's timeout argument to reflect time already slept, so 
eventually we finish. The MacOS (BSD) select() does not update the timeout argument and select goes back 
to sleep for another 2 seconds (to be again interrupted half-way through).

The POSIX standard (specification for select() & co) permits either behaviour. Compare "man select" on 
MacOS and on Linux.

If the select() timeout were not 2 seconds, but 0.9 seconds; or if the MIDAS watchdog alarm fired every 
2.1 seconds, this problem would also not exist.

I think there are several places in MIDAS with code like this. An audit is required.

{
                  FD_ZERO(&readfds);
                  FD_SET(_sock, &readfds);

                  timeout.tv_sec = 2;
                  timeout.tv_usec = 0;

                  do {
                     status = select(FD_SETSIZE, &readfds, NULL, NULL, &timeout);
                     /* if an alarm signal was cought, restart with reduced timeout */
                  } while (status == -1 && errno == EINTR);
}

K.O.

> The following code found in mhttpd does not work on MacOS (BSD UNIX). ...

Because of this problem, on MacOS, run transitions can get stuck forever - most timeouts do not work. (Specifically, recv_string() never times out)

K.O.

Record-oriented ODB functions db_create_record(), db_get_record(), db_check_record() and 
db_set_record() require special attention to the consistency between their "C struct"s (usually defined in 
midas.h), their initialization strings (usually defined in midas.h) and the contents of ODB.

When these 3 items become inconsistent, the corresponding midas functions tend to break.

Unlike ODB internal structures and event buffer internal structures, these record-oriented functions are 
not part of the midas binary-compatibility abi and they are not protected by db_validate_sizes().

From time to time, new items are added to some of these data structures. Usually this does not cause 
problems, but recently we had some difficulty with the runinfo and equipment structures, prompting this 
audit.

db_check_record: note: (C) means that this record is created there

alarm.c: alarm_odb_str(C)
mana.c: skipped
mfe.c: equipment_common_str, equipment_statistics_str(C), event_descrip(C), bank_list(C)
mhttpd.cxx: cgif_label_str(C), cgif_bar_str(C), runinfo_str(C), equipment_common_str(C)
mlogger.cxx: ch_settings_str(C)
sequencer.cxx: sequencer_str(C)

db_create_record:

alarm.c: alarm_odb_str, alarm_periodic_str, alarm_class_str
fal.c: skipped
mfe.c: equipment_common_str
midas.c: program_info_str (maybe)
odb.c: (maybe)
lazylogger.cxx: lazy_settings, lazy_statistics
mhttpd.cxx: runinfo_str
mlogger.cxx: chn_settings_str

db_get_record: (hard to do with grep, will have to check every db_get_record by hand)

alarm.c: alarm, class, program_info
fal.c: skipped
mana.c: skipped
midas.c: program_info
odb.c: (maybe)
lazylogger.cxx: lazyst
mhttpd.cxx: runinfo, equipment, ?hkeytemp?, chn_settings, chn_stats, ?label?, ?bar?
mlogger.cxx: ?, ?, chn_stats, chn, settings
sequencer.cxx: hkeyseq

db_set_record:

alarm.c: hkeyalarm, hkeyclass, ???, program_info
fal.c: skipped
mana.c: skipped
mfe.c: equipment_info, ?event structure?
odb.c: (maybe)
lazelogger.cxx: lazyst
mlogger.cxx: chn_stat
sequencer.cxx: seq

db_open_record: note: (W) means MODE_WRITE

fal.c: skipped
mana.c: skipped
mfe.c: equipment_info, equipment_stats(W)
midas.c: requested_transition
odbedit.c: key_update - generic test of hotlink
lazylogger.cxx: runstate, lazyst(W), lazy?
mlogger.cxx: history, chn_statistics, chn_settings
sequencer.cxx: seq

K.O.

The bulk of the MIDAS AJAX and Javascript functions is now documented on the MIDAS Wiki:

https://midas.triumf.ca/MidasWiki/index.php/Mhttpd.js
https://midas.triumf.ca/MidasWiki/index.php/AJAX

Enjoy,
K.O.

> The bulk of the MIDAS AJAX and Javascript functions is now documented on the MIDAS Wiki:
> 
> https://midas.triumf.ca/MidasWiki/index.php/Mhttpd.js
> https://midas.triumf.ca/MidasWiki/index.php/AJAX
> 

The documentation was updated again.

All functions and AJAX methods except jset, jget, jrpc (ODBGet, ODBSet, ODBRpc) and inline edit are now fully 
documented. AJAX methods jset/jget and their javascript wrappers ODBSet/ODBGet/ODBMGet/ODBGetRecord() are 
partially documented. Inline edit will have to be documented by Stefan.

When using these functions please read the "BUG" sections carefully.

When using the Javascript functions (ODBGet, ODBSet, ODBMCopy, etc) please pay special attention to the rules for URI-
encoding function arguments - some functions require that some arguments be pre-encoded by 
"encodeURIComponent()", some functions require some arguments to NOT be pre-encoded. The examples in 
examples/javascript1/example.html are mostly correct.

Special confusion is created by special handling in mhttpd of URI-encoding of parameters named "format".

Special confusion is created by ODBSet(path, value), where "path" should be pre-encoded, while "value" is now encoded 
internally, which is a recent change introduced with the inline edit function. Older versions of mhttpd.js still require that 
"value" be URI-encoded.

Going forward, I hope to resolve most of the confusion by providing a cleaner interface for reading ODB
- ODBMCopy() already looks good with full async JSON/JSONP support (already implemented)
- ODBMKey() to read just the keys, with async JSON/JSONP support (to be added)
- ODBMCreate() to create ODB keys (RPC for db_create()) (to be added)
- ODBMSet() to write into ODB. (to be added)

K.O.

> > The bulk of the MIDAS AJAX and Javascript functions is now documented on the MIDAS Wiki:
> > 
> > https://midas.triumf.ca/MidasWiki/index.php/Mhttpd.js
> > https://midas.triumf.ca/MidasWiki/index.php/AJAX
> > 
> 
> The documentation was updated again.
> 

Newly documented are the additional Javascript and AJAX functions present in the GIT branch "feature/ajax":

ODBMCreate(paths, types);
ODBMCreate(paths, types, arraylengths, stringlengths, callback);  
ODBMResize(paths, arraylengths, stringlengths, callback);  
ODBMRename(paths, names, callback);  
ODBMLink(paths, links, callback);  
ODBMReorder(paths, indices, callback);
ODBMKey(paths, callback);
ODBMDelete(paths, callback);

All these functions permit asynchronous use (with callback on completion) and the underlying AJAX functions permit JSON-P encoding.

ODBSetUrl("http://mhttpd.somewhere.com:8080") : this new function removes the restriction that custom scripts had to be loaded from the same mhttpd that they will 
access. Together with the newly added CORS support in mhttpd, allows loading custom scripts from any web server, including local file, and having then access any one (or 
any several) mhttpd data sources.

I think these new functions are now stable (I still had to make some changes to ODBMCreate() recently) and after some more testing this branch will be merged into 
"develop".

To use this branch, do either:
a) git clone midas; git pull; git checkout feature/ajax
b) git clone midas; git checkout develop; git pull; git checkout -b ajaxtest; git merge feature/ajax;

(Option (b) creates a local branch with the latest "develop" and "feature/ajax" merged together).

K.O.

I find that new mhttpd has strange behaviour for ODB strings.

- I create a new STRING variable in ODB through mhttpd.  It defaults to size 32.

- I then edit the STRING variable through mhttpd, writing a new string larger
than 32 characters.

- Initially everything looks fine; it seems as if the new string value has been
accepted.

- But if you reload the page, or navigate back to the page, you realize that
mhttpd has silently truncated the string back to 32 characters.

You can reproduce this problem on a test page here:

http://midptf01.triumf.ca:8081/AnnMessage

Older versions of mhttpd (I'm testing one from 2 years ago) don't have this
'feature'.  For older mhttpd the string variable would get resized when a larger
string was inputted.  That definitely seems like the right behavior to me.

I am using fresh copy of midas from bitbucket as of this morning. (How do I get
a particular tag/hash of the version of midas that I am using?)

I can confirm part of the problem - the new inline-edit function - after you finish editing - shows you what you 
have typed, not what's actually in ODB - at the very end it should do an ODBGet() to load the actual ODB 
contents and show *that* to the user.

The truncation to 32 characters - most likely it is a failure to resize the ODB string - is probably in mhttpd and 
I can take a quick look into it.

There is a 3rd problem - the mhttpd ODB editor "create" function does not ask for the string length to create.

Actually, in ODB, "create" and "set string size" are two separate functions - db_create_key(TID_STRING) creates 
a string of length zero, then db_set_data() creates an empty string of desired length.

In the new AJAX interface these two functions are separate (ODBCreate just calls db_create_key()).

In the present ODBSet() function the two are mixed together - and the ODB inline edit function uses ODBSet().

K.O.



> I find that new mhttpd has strange behaviour for ODB strings.
> 
> - I create a new STRING variable in ODB through mhttpd.  It defaults to size 32.
> 
> - I then edit the STRING variable through mhttpd, writing a new string larger
> than 32 characters.
> 
> - Initially everything looks fine; it seems as if the new string value has been
> accepted.
> 
> - But if you reload the page, or navigate back to the page, you realize that
> mhttpd has silently truncated the string back to 32 characters.
> 
> You can reproduce this problem on a test page here:
> 
> http://midptf01.triumf.ca:8081/AnnMessage
> 
> Older versions of mhttpd (I'm testing one from 2 years ago) don't have this
> 'feature'.  For older mhttpd the string variable would get resized when a larger
> string was inputted.  That definitely seems like the right behavior to me.
> 
> I am using fresh copy of midas from bitbucket as of this morning. (How do I get
> a particular tag/hash of the version of midas that I am using?)

I confirm the second part of the problem.

Inline edit uses ODBSet(), which uses the "jset" AJAX call to mhttpd which does not extend string variables.

This is the jset code. The best I can tell it truncates string variables to the existing size in ODB:

db_find_key(hDB, 0, str, &hkey)
db_get_key(hDB, hkey, &key);
memset(data, 0, sizeof(data));
size = sizeof(data);
db_sscanf(getparam("value"), data, &size, 0, key.type);
db_set_data_index(hDB, hkey, data, key.item_size, index, key.type);

These original jset/jget functions are a little bit too complicated and there is no documentation (what exists is done by me trying to read the existing code).

We now have a jcopy/ODBMCopy() as a sane replacement for jget, but nothing comparable for jset, yet.

I think this quirk of inline edit cannot be fixed in javascript - the mhttpd code for "jset" has to change.

K.O.


> 
> I can confirm part of the problem - the new inline-edit function - after you finish editing - shows you what you 
> have typed, not what's actually in ODB - at the very end it should do an ODBGet() to load the actual ODB 
> contents and show *that* to the user.
> 
> The truncation to 32 characters - most likely it is a failure to resize the ODB string - is probably in mhttpd and 
> I can take a quick look into it.
> 
> There is a 3rd problem - the mhttpd ODB editor "create" function does not ask for the string length to create.
> 
> Actually, in ODB, "create" and "set string size" are two separate functions - db_create_key(TID_STRING) creates 
> a string of length zero, then db_set_data() creates an empty string of desired length.
> 
> In the new AJAX interface these two functions are separate (ODBCreate just calls db_create_key()).
> 
> In the present ODBSet() function the two are mixed together - and the ODB inline edit function uses ODBSet().
> 
> K.O.
> 
> 
> 
> > I find that new mhttpd has strange behaviour for ODB strings.
> > 
> > - I create a new STRING variable in ODB through mhttpd.  It defaults to size 32.
> > 
> > - I then edit the STRING variable through mhttpd, writing a new string larger
> > than 32 characters.
> > 
> > - Initially everything looks fine; it seems as if the new string value has been
> > accepted.
> > 
> > - But if you reload the page, or navigate back to the page, you realize that
> > mhttpd has silently truncated the string back to 32 characters.
> > 
> > You can reproduce this problem on a test page here:
> > 
> > http://midptf01.triumf.ca:8081/AnnMessage
> > 
> > Older versions of mhttpd (I'm testing one from 2 years ago) don't have this
> > 'feature'.  For older mhttpd the string variable would get resized when a larger
> > string was inputted.  That definitely seems like the right behavior to me.
> > 
> > I am using fresh copy of midas from bitbucket as of this morning. (How do I get
> > a particular tag/hash of the version of midas that I am using?)

> This is the jset code. The best I can tell it truncates string variables to the existing size in ODB:
> 
> db_find_key(hDB, 0, str, &hkey)
> db_get_key(hDB, hkey, &key);
> memset(data, 0, sizeof(data));
> size = sizeof(data);
> db_sscanf(getparam("value"), data, &size, 0, key.type);
> db_set_data_index(hDB, hkey, data, key.item_size, index, key.type);


Correct. So I added some code which extends strings if necessary (NOT string arrays, they are more complicated to handle).

Actually this was no bug, but a missing feature. Strings were never meant to be extended via the web interface. 
Now I added that feature to the current version. Please check it.

/Stefan

I would like to share with you a silly problem with mktime() and daylight savings time (Summer 
time/Winter time) that I have run into while working on the mhttpd history query page.

I am implementing 1 hour granularity for the queries (was 1 day granularity) and somehow all my queries 
were off by 1 hour.

It turns out that the mktime() and localtime() functions for converting between time_t and normal time 
units (days, hours) are not exact inverses of each other.

Daylight savings time (DST) is to blame.

While localtime() always applies the current DST,  mktime() will return the wrong answer unless tm_isdst is 
set correctly.

For tm_isdst, the default value 0 is wrong 50% of the time in most locations as it means "DST off" (whether 
that's Summer time or Winter time depends on your location).

Today in Vancouver, BC, DST is in effect, and localtime(mktime()) is off by 1 hour.

If I were doing this in January, I would not see this problem.

"man mktime" talks about "tm_isdst" special value "-1" that is supposed to fix this. But the wording of 
"man mktime" on Linux and on MacOS is different (I am amused by the talk about "attempting to divine 
the DST setting"). Wording at http://pubs.opengroup.org/onlinepubs/007908799/xsh/mktime.html is 
different again. MS Windows (Visual Studio) documentation says different things for different versions.

So for mhttpd I use the following code. First mktime() gets the approximate time, a call to localtime() 
returns the DST setting in effect for that date, a second mktime() with the correct DST setting returns the 
correct time. (By "correct" I mean that localtime(mktime(t)) == t).

time_t mktime_with_dst(const struct tm* ptms)
{
   // this silly stuff is required to correctly handle daylight savings time (Summer time/Winter time)
   // when we fill "struct tm" from user input, we cannot know if daylight savings time is in effect
   // and we do not know how to initialize the value of tms->tm_isdst.
   // This can cause the output of mktime() to be off by one hour.
   // (Rules for daylight savings time are set by national and local govt and in some locations, changes 
yearly)
   // (There are no locations with 2 hour or half-hour daylight savings that I know of)
   // (Yes, "man mktime" talks about using "tms->tm_isdst = -1")
   //
   // We assume the user is using local time and we convert in two steps:
   //
   // first we convert "struct tm" to "time_t" using mktime() with unknown tm_isdst
   // second we convert "time_t" back to "struct tm" using localtime_r()
   // this fills "tm_isdst" with correct value from the system time zone database
   // then we reset all the time fields (except for sub-minute fields not affected by daylight savings)
   // and call mktime() again, now with the correct value of "tm_isdst".
   // K.O. 2013-09-14

   struct tm tms = *ptms;
   struct tm tms2;
   time_t t1 = mktime(&tms);
   localtime_r(&t1, &tms2);
   tms2.tm_year = ptms->tm_year;
   tms2.tm_mon  = ptms->tm_mon;
   tms2.tm_mday = ptms->tm_mday;
   tms2.tm_hour = ptms->tm_hour;
   tms2.tm_min  = ptms->tm_min;
   time_t t2 = mktime(&tms2);
   //printf("t1 %.0f, t2 %.0f, diff %d\n", (double)t1, (double)t2, (int)(t1-t2));
   return t2;
}

K.O.

I vaguely remember that I had a similar problem with ELOG. The solution was to call tzset() at the beginning of the program. The man page says that 
this function is called automatically by programs using time zones, but apparently it is not. Can you try that? There is also the TZ environment 
variable and /etc/localtime. I never understood the details, but playing with these things can influence mktime() and localtime().

/Stefan

> I vaguely remember that I had a similar problem with ELOG. The solution was to call tzset() at the beginning of the program. The man page says that 
> this function is called automatically by programs using time zones, but apparently it is not. Can you try that? There is also the TZ environment 
> variable and /etc/localtime. I never understood the details, but playing with these things can influence mktime() and localtime().

I confirm that the timezone is set correctly - I do get the correct time eventually - so there is no missing call to tzet().

K.O.

> > I vaguely remember that I had a similar problem with ELOG. The solution was to call tzset() at the beginning of the program. The man page says that 
> > this function is called automatically by programs using time zones, but apparently it is not. Can you try that? There is also the TZ environment 
> > variable and /etc/localtime. I never understood the details, but playing with these things can influence mktime() and localtime().
> 
> I confirm that the timezone is set correctly - I do get the correct time eventually - so there is no missing call to tzet().
> 
> K.O.

tzset() not only sets the time zone, but also DST.

> > > I vaguely remember that I had a similar problem with ELOG. The solution was to call tzset() at the beginning of the program. The man page says that 
> > > this function is called automatically by programs using time zones, but apparently it is not. Can you try that? There is also the TZ environment 
> > > variable and /etc/localtime. I never understood the details, but playing with these things can influence mktime() and localtime().
> > 
> > I confirm that the timezone is set correctly - I do get the correct time eventually - so there is no missing call to tzet().
> > 
> > K.O.
> 
> tzset() not only sets the time zone, but also DST.

I found following code in elogd.c, maybe it helps:

/* workaround for wong timezone under MAX OSX */
long my_timezone()
{
#if defined(OS_MACOSX) || defined(__FreeBSD__) || defined(__OpenBSD__)
   time_t tp;
   time(&tp);
   return -localtime(&tp)->tm_gmtoff;
#else
   return timezone;
#endif
}



void get_rfc2822_date(char *date, int size, time_t ltime)
{
   time_t now;
   char buf[256];
   int offset;
   struct tm *ts;

   /* switch locale temporarily back to english to comply with RFC2822 date format */
   setlocale(LC_ALL, "C");

   if (ltime == 0)
      time(&now);
   else
      now = ltime;
   ts = localtime(&now);
   assert(ts);
   strftime(buf, sizeof(buf), "%a, %d %b %Y %H:%M:%S", ts);
   offset = (-(int) my_timezone());
   if (ts->tm_isdst)
      offset += 3600;
   snprintf(date, size - 1, "%s %+03d%02d", buf, (int) (offset / 3600),
            (int) ((abs((int) offset) / 60) % 60));
}

Dear MIDAS programmers,

I have been using your software in my lab (APC, Paris)
to run our data acqusition system. It is very robust and flexible.s

I would like to give you the large amount of credit which you are due.
How should I cite both MIDAS and ROODY? I have not been able to find any
information in the usual places.

Cheers, and thanks for the great program!
-Carl

> 
> I have been using your software in my lab (APC, Paris)
> to run our data acqusition system. It is very robust and flexible.s
> 
> I would like to give you the large amount of credit which you are due.
> How should I cite both MIDAS and ROODY? I have not been able to find any
> information in the usual places.
> 

Good to hear from a happy user.

I think the best way to give us credit is to recommend MIDAS to 10 of your friends.

For MIDAS citations, I think Pierre and Stefan have a standard one somewhere, we should have it linked from 
midas.triumf.ca.

For ROODY citations, I am not sure we have one. The idea behind it was to make a ROOT version of PAW++. 
Main authors are Greg King (UBC COOP student, where is he now?), Joe Chuma (also author of PHYSICA, 
R.I.P.), Pierre Amaudruz, myself and a few others.

K.O.

> Dear MIDAS programmers,
> 
> I have been using your software in my lab (APC, Paris)
> to run our data acqusition system. It is very robust and flexible.s
> 
> I would like to give you the large amount of credit which you are due.
> How should I cite both MIDAS and ROODY? I have not been able to find any
> information in the usual places.
> 
> Cheers, and thanks for the great program!
> -Carl

The standard citation for midas is a link to

http://midas.psi.ch

At the moment this points automatically to http://midas.triumf.ca, so both institutes are credited.

/Stefan

Javascript "AJAX" functions (and their MIDAS wrappers - ODBGet/ODBSet) are subject to something called 
"same origin policy" intended to prevent something called "cross-site scripting attacks", i.e. see
http://en.wikipedia.org/wiki/Same-origin_policy

In practice it means that if you load the MIDAS custom web page from test.foo.com and try to access 
mhttpd at midas.foo.com, ODBSet/ODBGet will not work.

I always thought that this meant that the requests are blocked by the browser and are a form of 
protection of the web server - only scripts loaded from mhttpd can do AJAX (ODBGet/ODBSet) to mhttpd.

It turns out that I was wrong. This is what actually happens: the "cross-site" requests are still sent to the 
server (mhttpd), the response it received, parsed and discarded if "same origin" conditions are not met.

This means that the "same origin" policy does not protect mhttpd at all - any script from any page 
anywhere can issue AJAX requests into any mhttpd, these requests will be successfully sent, received
and processed by mhttpd, including requests for writing into ODB ("jset" command using the HTTP GET 
method).

So for the case of MIDAS, "same origin" does not prevent malicious (or buggy) scripts from writing into the 
wrong mhttpd of the wrong experiment.

All it does is prevent desired and intentional access to mhttpd (ODBGet) from scripts that happen to have 
been loaded outside of mhttpd (i.e. from a developer own test page).

Then it turns out that there is an "official" way to disable this unwanted protection policy, called CORS, see
http://www.w3.org/TR/cors/

I have now implemented this in mhttpd and added an mhttpd.js function ODBSetURL() to explicitly set the 
URL of mhttpd that we want to talk to.

This work is on the feature/ajax branch, to be merged soon. For the impatient, here is what you need to 
do in mhttpd:

diff --git a/src/mhttpd.cxx b/src/mhttpd.cxx
index 1d9d1cc..0460cec 100755
--- a/src/mhttpd.cxx
+++ b/src/mhttpd.cxx
@@ -1070,6 +1070,7 @@ void show_text_header()
 {
    rsprintf("HTTP/1.0 200 Document follows\r\n");
    rsprintf("Server: MIDAS HTTP %d\r\n", mhttpd_revision());
+   rsprintf("Access-Control-Allow-Origin: *\r\n");
    rsprintf("Pragma: no-cache\r\n");
    rsprintf("Expires: Fri, 01 Jan 1983 00:00:00 GMT\r\n");
    rsprintf("Content-Type: text/plain; charset=iso-8859-1\r\n\r\n");

K.O.

As of commit
https://bitbucket.org/tmidas/midas/commits/dfa5fb1a93cae11a2960d441044c7fd277e1f0ec
(we are now liberated from the tyranny of SVN IDs),
multithreaded run transitions seem to work reliably and are now the default in mhttpd.

In odbedit and mtransition, the default is the old sequential transitions. "-m" and "-a" flags activate 
the new multithread run transitions. mhttpd now uses the equivalent of "mtransition -a" 
(mutithreaded asynchronous).

This is one of the new features implemented by Stefan while at TRIUMF.

K.O.

(We hope to write up all the recent changes soon).

odbedit uses a fixed size buffer for ODB data. If an array in ODB is bugger than this size, 
db_get_data() correctly returns DB_TRUNCATED and there is no memory overwrite, but the following 
code for printing the data does not know about this truncation and proceeds printing memory 
values contained after the end of the fixed size data buffer - in the current case, this memory 
somehow had the contents of the shell history - this very confused the MIDAS users as they though 
that the funny printout was actually in ODB. This is in the print_key() function. If db_get_data() 
returns DB_TRUNCATED, it should allocate a buffer of bigger size. This (and the previous) bug found 
by the TIGRESS experiment. K.O.

The odb.c function merge_records() has a fixed size array of 10000 bytes to handle the data and it 
aborts with an assert() if passed data bigger than that. It is called from db_create_record() which 
already allocates a data buffer of correct size for it's operations.
K.O.

We are happy to announce the creation of the MidasWiki at TRIUMF (https://midas.triumf.ca) as the 
new location of MIDAS documentation, user instructions, examples, etc.

https://midas.triumf.ca
K.O.

> We are happy to announce the creation of the MidasWiki at TRIUMF
> https://midas.triumf.ca

We are running MediaWiki in the world-readable, authenticated-user-writable mode.

New user registration is done by the "confirm new user" extension (https://www.mediawiki.org/wiki/Extension:ConfirmAccount):
- go to https://midas.triumf.ca/MidasWiki/index.php/Special:RequestAccount
- fill the form, submit request - request goes to wiki administrator for confirmation
- wait for email about email address confirmation, follow instructions to confirm your email address
- wait for email about account confirmation
- try to login to the wiki.

K.O.

The MIDAS source code repository was converted from SVN to GIT, hosted as bitbucket: 
https://bitbucket.org/tmidas.

A clonable copy of the repository is located at TRIUMF: git clone 
http://daq.triumf.ca/~daqweb/git/midas.git (and mxml.git).

The documentation is being slowly updated with GIT instructions (git clone) instead of SVN (svn 
checkout).

The MIDAS code history goes all the way to CVS/SVN rev 1 dated Thu Oct 8 13:46:02 1998.

K.O.

Konstantin forgot to tell people outside of TRIUMF how to get the newest version of MIDAS. Here it is:

$ git clone https://bitbucket.org/tmidas/midas.git

Not that you can also browse the repository at

https://bitbucket.org/tmidas/midas

On some (older) systems, you might have to install git (http://git-scm.com/downloads).

/Stefan

The HTTPS SSL certificate on ladd00.triumf.ca has been updated. Same as the old
certificate, the new one is self-signed and your web browser may complain about
that and ask you to "save a security exception".

When you save the new certificate, you can verify that you are connected to the
real ladd00.triumf.ca by comparing the "SHA1 fingerprint" reported by your web
browser to the one given below (as reported by "svn update"):

Certificate information:
 - Hostname: ladd00.triumf.ca
 - Valid: from Mon, 10 Jun 2013 18:43:19 GMT until Tue, 10 Jun 2014 18:43:19 GMT
 - Issuer: DAQ, TRIUMF, Vancouver, BC, CA
 - Fingerprint: 3f:15:d0:1d:68:ae:f0:73:10:78:84:66:f3:af:c7:67:5c:70:00:62

At the same time, elogd was updated to latest version from Stefan (elog-2.9.2-1.i386).

Also as part of local computer updates, elogd is temporarily running on ladd03.triumf.ca. This should be 
transparent to all users but please let me know if there are strange artefacts, etc. (ladd03 will become the 
new ladd00 "soon").

K.O.

I updated the MIDAS javascript examples in examples/javascript1. All existing mhttpd.js functions are 
now exampled. (yes).

Here is the full list of functions, with notes:

ODBSet(path, value, pwdname);
ODBGet(path, format, defval, len, type);
ODBMGet(paths, callback, formats); --- doc incomplete - no example of callback() use
ODBGetRecord(path);
ODBExtractRecord(record, key);
new ODBKey(path); --- doc incomplete, wrong - one has to use "new ODBKey" - last_used was added.
ODBCopy(path, format); -- no doc
ODBRpc_rev0(name, rpc, args); --- doc refer to example
ODBRpc_rev1(name, rpc, max_reply_length, args); --- same
ODBGetMsg(n);
ODBGenerateMsg(m);
ODBGetAlarms(); --- no doc
ODBEdit(path); --- undoc - forces page reload

As annotated, the main documentation is partially incomplete and partially wrong (i.e. ODBKey() has to be 
invoked as "new ODBKey()"). I hope this will be corrected soon. In the mean time, I recommend that 
everybody uses this example as best documentation available.
http://ladd00.triumf.ca/~daqweb/doc/midas/html/RC_mhttpd_custom_js_lib.html

svn rev 5360
K.O.

> ODBCopy(path, format); -- no doc

Updated example of ODBCopy:

format="" returns data in traditional ODB save format
format="xml" returns data in XML encoding
format="json" returns data in JSON encoding.

K.O.

If the MIDAS Alarm property "write elog message" is enabled, an uninitialized variable "tag" is passed to 
el_submit() and depending on your luck, cause a crash. "tag" is supposed to be and is now a NUL-
terminated string. The only other use of el_submit() is in mhttpd.cxx and mserver.c, where it is called 
correctly.

alarm.c svn rev 5361
K.O.

The MIDAS web page at TRIUMF (http://midas.triumf.ca) moved from the daq-plone site to the DAQWiki 
(MediaWiki) site. Links were updated, checked and corrected:
https://www.triumf.info/wiki/DAQwiki/index.php/MIDAS

Included is the link to our MIDAS installation instructions. These are more complete compared to the 
instructions in the MIDAS documentation:
https://www.triumf.info/wiki/DAQwiki/index.php/Setup_MIDAS_experiment
K.O.