> time to choose the next c++!

Ununtu-24.04, MIDAS builds with -std=c++23 without errors or any additional warnings. (but does it work? "make 
test" is ok).

K.O.

As part of discussions with Stefan during the MIDAS workshop,
an update to supported versions of c++ on different platforms.

- el6/SL6 is gone, gcc 4.4.7, no c++11
- el7/CentOS-7 is out the door, gcc 4.8.5, full c++11, no c++14, no c++17
- el8 was a still born child of RedHat
- el9  - gcc 11.5 with 12, 13, and 14 available, incomplete c++26, c++23, experimental c++20, default c++17
- el10 - gcc 14.2, incomplete c++26, c++23, experimental c++20, default c++17

- U-18 - gcc  7.5, experimental, incomplete c++17
- U-20 - gcc  9.4 default, 10.5 available, experimental, incomplete c++17
- U-22 - gcc 11.4 default, 12.3 available, default c++17
- U-24 - gcc 13.3 default, 14.2 available, default c++17

- D-11 - gcc 10.2, experimental c++17
- D-12 - gcc 12.2, default c++17

- MacOS 15.2 - llvm/clang 16, default c++17
- MacOS 15.7 - llvm/clang 17, default c++17

Taken from C++ level support:

GCC C++ support: https://gcc.gnu.org/projects/cxx-status.html
LLVM clang c++ support: https://clang.llvm.org/cxx_status.html
GLIBC c++ support: https://gcc.gnu.org/onlinedocs/libstdc++/manual/status.html

This suggests that c++17 is available on all current platforms.

K.O.

P.S. ROOT moved to C++17 as of release 6.30 on November 6, 2023.

Following discussions at the MIDAS workshop, we propose to move MIDAS from c++11 to c++17. There is 
many new features and we want to start using some of them.

Per my previous message https://daq00.triumf.ca/elog-midas/Midas/3084,
c++17 is available on current MacOS, U-22 and newer, el9 and newer, D-12 and newer.

(ROOT moved to C++17 as of release 6.30 on November 6, 2023)

As I reported earlier, MIDAS already builds with c++23 on U-24, and this move does not require any 
actual code changes other than a bump of c++ version in CMakeLists.txt and Makefile.

Please let us know if this change will cause problems or if you think that we should move to an older 
c++ (c++14) or newer c++ (c++20 or c++23 or c++26).

If we do not hear anything, we will implement this change in about 2-3 weeks.

K.O.

perhaps c++20? - std::format is an immediately useful feature. --regards, Pasha

> Following discussions at the MIDAS workshop, we propose to move MIDAS from c++11 to c++17. There is 
> many new features and we want to start using some of them.
> 
> Per my previous message https://daq00.triumf.ca/elog-midas/Midas/3084,
> c++17 is available on current MacOS, U-22 and newer, el9 and newer, D-12 and newer.
> 
> (ROOT moved to C++17 as of release 6.30 on November 6, 2023)
> 
> As I reported earlier, MIDAS already builds with c++23 on U-24, and this move does not require any 
> actual code changes other than a bump of c++ version in CMakeLists.txt and Makefile.
> 
> Please let us know if this change will cause problems or if you think that we should move to an older 
> c++ (c++14) or newer c++ (c++20 or c++23 or c++26).
> 
> If we do not hear anything, we will implement this change in about 2-3 weeks.
> 
> K.O.

> perhaps c++20? - std::format is an immediately useful feature. --regards, Pasha

confirmed. std::format is an improvement over K&R C printf().

but seems unavailable on U-20 and older, requires --std=c++20 on U-24 and MacOS.

but also available as a standalone library: https://github.com/fmtlib/fmt

myself, I use printf() and msprintf(), I think std::format is in the "too little, too late to save C++" 
department.

K.O.

> > perhaps c++20? - std::format is an immediately useful feature. --regards, Pasha
> 
> confirmed. std::format is an improvement over K&R C printf().
> 
> but seems unavailable on U-20 and older, requires --std=c++20 on U-24 and MacOS.

agreed! - availability is significantly more important. -- regards, Pasha

Hi, Stefan & co - now that midas is c++11 and c++11 comes with a threads library, should we 
switch midas to use the c++11 threads instead of pthreads? (Of course on Linux c++11 
threads are a layer on top of pthreads, the best I know).

This should remove the dependency on pthreads.h and use a more native implementation of 
threads on MacOS and Windows. (again, the best I can tell).

Of course this depends on c++11 threads having all the functions we need. Specifically, "lock 
with timeout" is useful to deal with "gah! everything stopped! what do I do!", a problem 
bedeviling midas in the early days (and still happens today!). Current midas kills everything 
after 5 minutes of deadlock - then the user knows how to restart everything and the developer 
has core dumps to look at. (to see which program/thread holds the lock and would not give it 
up).

Any thoughts on this?

K.O.

I'm thinking of this already since some time, and it was part of my motivation switching to C++11.
I was delighted to see that what we do in system.c (encapsulate system functions such as threads
and shared memory) is now done natively in C++11, and it's done by experts and not amateurs like us.

I see that with std::timed_mutex and try_lock_for we have the desired timeout function. Pity that
C++11 does not contain inter-process communication like semaphores, so there we still have to use
our old functions. 

But for threads switching to std::thread, I'm all in.

Stefan

> Hi, Stefan & co - now that midas is c++11 and c++11 comes with a threads library, should we 
> switch midas to use the c++11 threads instead of pthreads? (Of course on Linux c++11 
> threads are a layer on top of pthreads, the best I know).
> 
> This should remove the dependency on pthreads.h and use a more native implementation of 
> threads on MacOS and Windows. (again, the best I can tell).
> 
> Of course this depends on c++11 threads having all the functions we need. Specifically, "lock 
> with timeout" is useful to deal with "gah! everything stopped! what do I do!", a problem 
> bedeviling midas in the early days (and still happens today!). Current midas kills everything 
> after 5 minutes of deadlock - then the user knows how to restart everything and the developer 
> has core dumps to look at. (to see which program/thread holds the lock and would not give it 
> up).
> 
> Any thoughts on this?
> 
> K.O.

> Hi, Stefan & co - now that midas is c++11 and c++11 comes with a threads library, should we 
> switch midas to use the c++11 threads instead of pthreads? (Of course on Linux c++11 
> threads are a layer on top of pthreads, the best I know).
> 
> This should remove the dependency on pthreads.h and use a more native implementation of 
> threads on MacOS and Windows. (again, the best I can tell).
> 
> Of course this depends on c++11 threads having all the functions we need. Specifically, "lock 
> with timeout" is useful to deal with "gah! everything stopped! what do I do!", a problem 
> bedeviling midas in the early days (and still happens today!). Current midas kills everything 
> after 5 minutes of deadlock - then the user knows how to restart everything and the developer 
> has core dumps to look at. (to see which program/thread holds the lock and would not give it 
> up).
> 
> Any thoughts on this?
> 
> K.O.

Hi, I just wanted to say that I have seen this post and maybe that is the solution to the pthreads compiler problem in OS 10.15, but 
of course I am a total amateur in here. Thanks for thinking about this and I will wait and hold to see what gets decided. Thanks

Berta  

 Hi,
I was trying to update the checkout of Midas, but it looks like something is not
working - maybe a component of the Savannah system:
[sergio@daq-pc midas-SVN]$ svn update
svn@savannah.psi.ch's password: svn
unix dgram connect: Connection refused at /bin/cvssh.pl line 32
no connection to syslog available at /bin/cvssh.pl line 32
svn: Connection closed unexpectedly

my .svn/entries says (amongst the rest)
 url="svn+ssh://svn@savannah.psi.ch/afs/psi.ch/project/meg/svn/midas/trunk"
and yes, it used to work well... 

Cheers,
  Sergio

>  Hi,
> I was trying to update the checkout of Midas, but it looks like something is not
> working - maybe a component of the Savannah system:
> [sergio@daq-pc midas-SVN]$ svn update
> svn@savannah.psi.ch's password: svn
> unix dgram connect: Connection refused at /bin/cvssh.pl line 32
> no connection to syslog available at /bin/cvssh.pl line 32
> svn: Connection closed unexpectedly
> 
> my .svn/entries says (amongst the rest)
>  url="svn+ssh://svn@savannah.psi.ch/afs/psi.ch/project/meg/svn/midas/trunk"
> and yes, it used to work well... 
> 
> Cheers,
>   Sergio

I just tried now and it seemed to work fine. Do you still have the problem?

- Stefan

> I just tried now and it seemed to work fine. Do you still have the problem?
> 
> - Stefan

 The problem was still there this morning, shortly after seeing your mail, but seems
to be fixed now.
 BTW, which is the best way to submit patches ? I have a version of khyt1331 for Linux
kernel 2.6 (we are running Scientific Linux 4.1), and a few smaller things, mostly in
the examples. 

 Thanks, Sergio

Fuming, fuming, fuming.

The combination of "make indent" and "svn update" completely trashed my work copy of midas. Half of 
the files now show as status "M", half as status "C" ("in conflict"), even those I never edited myself (e.g. 
mscb firmware files).

I think what happened as that once I ran "make indent", the indent program did things to the source 
files (changed indentation, added spaces in "foo(a,b,c); --> foo(a, b, c);" etc, so now svn thinks that I 
edited the files and they are in conflict with later modifications.

I suggest that nobody ever ever ever should use "make indent", and if they do, they should better 
commit their "changes" made by indent very quickly, before their midas tree is trashed by the next "svn 
update".

And if they commit the changes made by "make indent", beware that "make indent" is not idempotent, 
running it multiple times, it keeps changing files (keeps moving some dox comments around).

Also beware of entering a tug-of-war with Stefan - at least on my machines, my "make indent" seems 
to produce different output from his.

Still fuming, even after some venting...
K.O.

> >
> > .../c++  ...  /opt/local/lib/libssl.dylib
> >
> 
> I get the same, libssl from /opt/local, so we are not using openssl shipped with mac os.
> 

I note that latest mongoose 6.16 finally has a virtual ssl layer and appears to support mbedtls (polarssl) in addition to openssl.

I now think I should see if it works - as it gives us a way to support https without relying on the user having
pre-installed working openssl packages - we consistently run into problems with openssl on macos, and even
on linux there was trouble with preinstalled openssl packages and libraries.

With mbedtls, one will have to "git pull" and "make" it, but historically this causes much less trouble.

Also, with luck, mbedtls has better support for certificate expiration (I would really love to have openssl report an error
or a warning or at least some hint if I feed it an expired certificate) and (gasp!) certbot integration.

K.O.

> ... support for certbot

The certbot tool to use instead of certbot is this: https://github.com/ndilieto/uacme

K.O.

> > ... support for certbot
> 
> The certbot tool to use instead of certbot is this: https://github.com/ndilieto/uacme
> 
> K.O.


HI Stefan and Konstantin, 

Thanks a lot for your messages. Sorry for my late reply, I only work on this project from Tuesday to Thursdays. I have 
run " make cmake" instead of "cd build; cmake" and this is the output regarding mhttpd:

/Library/Developer/CommandLineTools/usr/bin/c++  -O2 -g -DNDEBUG -Wl,-search_paths_first -Wl,-
headerpad_max_install_names  CMakeFiles/mhttpd.dir/mhttpd.cxx.o CMakeFiles/mhttpd.dir/mongoose6.cxx.o 
CMakeFiles/mhttpd.dir/mgd.cxx.o CMakeFiles/mhttpd.dir/__/mscb/src/mscb.cxx.o  -o mhttpd  -lsqlite3 ../libmidas.a 
/usr/lib/libssl.dylib /usr/lib/libcrypto.dylib -lz -lsqlite3 /usr/lib/libssl.dylib /usr/lib/libcrypto.dylib -lz 
Undefined symbols for architecture x86_64:
  "_OPENSSL_init_ssl", referenced from:
      _mg_mgr_init in mongoose6.cxx.o
  "_SSL_CTX_set_options", referenced from:
      _mg_set_ssl in mongoose6.cxx.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)


I see that in your outputs the openssl libs are in /opt/local/lib/ while mine are in /usr/lib/, and that is the only difference. 
I have checked that the libraries libssl.dylib and libcrypto.dylib are in my /usr/lib/, and indeed they are, so I don't 
understand the reason for the error, I will continue investigating. 

Thanks 

Berta 

> I only work on this project from Tuesday to Thursdays.

No problem. No hurry.

> I have run " make cmake" instead of "cd build; cmake" and this is the output regarding mhttpd: ...

There should be also a line where mhttpd.cxx is compiled into mhttpd.o, we need to see what compiler
flags are used - I suspect the compiler uses header files from /usr/local/include while the linker
is using libraries from /usr/lib, a mismatch.

To save time, please attach the full output of "make cmake". There may be something else I want to see there.

If you do not use the mhttpd built-in https support (for best security I recommend using https from the apache httpd password protected https proxy),
then it is perfectly fine to build midas with NO_SSL=1.

K.O.

FILE history code (mhf_*.dat files) did not support reading history files bigger than about 2GB, this is now 
fixed on branch "feature/history_off64_t" (in final testing, to be merged ASAP).

History files were never meant to get bigger than about 100 MBytes, but it turns out large files can still 
happen:

1) files are rotated only when history is closed and reopened
2) we removed history close and open on run start
3) so files are rotated only when mlogger is restarted

In the old code, large files would still happen if some equipment writes a lot of data (I have a file from 
Stefan with history record size about 64 kbytes, written at 1/second, MIDAS handles this just fine) or if 
there is no runs started and stopped for a long time.

There are reasons for keeping file size smaller:

a) I would like to use mmap() to read history files, and mmap() of a 100 Gbyte file on a 64 Gbyte RAM 
machine would not work very well.
b) I would like to implement compressed history files and decompression of a 100 Gbyte file takes much 
longer than decompression of a 100 Mbyte file. it is better if data is in smaller chunks.

(it is easy to write a utility program to break-up large history files into smaller chunks).

Why use mmap()? I note that the current code does 1 read() syscall per history record (it is much better to 
read data in bigger chunks) and does multiple seek()/read() syscalls to find the right place in the history 
file (plays silly buggers with the OS read-ahead and data caching). mmap() eliminates all syscalls and has 
the potential to speed things up quite a bit.

K.O.

Please be aware of mlogger.c update rev 4566 on Sept 23rd 2009, when Stefan
fixed a buglet in the subrun file size computations. Before this fix, the first
subrun could be of a short length. If you use subruns, please update your
mlogger to at least rev 4566 (or newer, Stefan added the run and subrun time
limits just recently).
K.O.

Hi,

I was wondering if there is a "mechanism" to run an executable
file after each subrun is closed...

I need to convert .mid.lz4 subrun files to ROOT (TTree) files;

Thanks,
Gennaro