Hi all,

last week I was running MIDAS with the commit 3ad98c5. Today I updated MIDAS and now all my watch functions are crashing. Attached I have a minimal example frontend of the problem.

In our software we have two functions one which sets up the ODB values of the frontend and another one which sets up all watch functions. So overall we connect two time to the ODB during fronend_init one time to create the values and one time to create the watch. In the example code a simple version of this setup is shown:

INT frontend_init() {

  cm_msg(MINFO, "frontend_init() setup", "Test FE");

  odb settings = {
    {"Test", 123},
    {"sub", {}}
  };
  settings.connect_and_fix_structure("/Equipment/Test FE/Settings");
  // settings.watch(watch); <-- this works without segmentation fault

  odb new_settings("/Equipment/Test FE/Settings");
  new_settings.watch(watch); // <-- here I am getting a segmentation fault

  return CM_SUCCESS;
}

When I directly set the watch everything runs fine however, when I create a new ODB object and use this one to set a watch I am getting the following segmentation fault:

Process 18474 stopped
* thread #1, queue = 'com.apple.main-thread', stop reason = EXC_BAD_ACCESS (code=1, address=0x34)
    frame #0: 0x000000010004fa38 test_fe`midas::odb::watch_callback(hDB=<unavailable>, hKey=<unavailable>, index=0, info=0x00006000002001c0) at odbxx.cxx:96:25 [opt]
   93  	      if (po->m_data == nullptr)
   94  	         mthrow("Callback received for a midas::odb object which went out of scope");
   95  	      midas::odb *poh = search_hkey(po, hKey);
-> 96  	      poh->m_last_index = index;
   97  	      po->m_watch_callback(*poh);
   98  	      poh->m_last_index = -1;
   99  	   }

Best,
Marius

#include <algorithm>
#include <math.h>
#include <random>
#include <array>
#include <string>
#include <stdio.h>
#include <stdlib.h>

#include "midas.h"
#include "msystem.h"
#include "odbxx.h"
#include "mfe.h"

using namespace std;
using midas::odb;


/*-- Globals -------------------------------------------------------*/
/* The frontend name (client name) as seen by other MIDAS clients   */
const char *frontend_name = "Test FE";
/* The frontend file name, don't change it */
const char *frontend_file_name = __FILE__;

/* frontend_loop is called periodically if this variable is TRUE    */
BOOL frontend_call_loop = FALSE;

/* a frontend status page is displayed with this frequency in ms    */
INT display_period = 0;

/* maximum event size produced by this frontend */
INT max_event_size = 32 * (1024 * 1024); // 32MiB

/* maximum event size for fragmented events (EQ_FRAGMENTED) */
INT max_event_size_frag = 5 * 1024 * 1024;

/* buffer size to hold events */
INT event_buffer_size = 4 * max_event_size;

BOOL equipment_common_overwrite = TRUE;//true is overwriting the common odb

/*-- Function declarations -----------------------------------------*/
INT read_odb(char * pevent, INT);
void watch(odb o);
/*-- Equipment list ------------------------------------------------*/

EQUIPMENT equipment[] = {

  {
    "Test FE",      /* equipment name */
    {1, 0,          /* event ID, trigger mask */
    "SYSTEM",      /* event buffer */
    EQ_PERIODIC,   /* equipment type */
    0,             /* event source */
    "MIDAS",       /* format */
    TRUE,          /* enabled */
    RO_ALWAYS | RO_ODB,  /* read always and update ODB */
    1000,          /* read every 1 sec */
    0,             /* stop run after this event limit */
    0,             /* number of sub events */
    0,             /* log history every event */
    "", "", ""},
    read_odb,       /* readout routine */
  },

  {""}};

/*-- Dummy routines ------------------------------------------------*/

INT poll_event(INT, INT count, BOOL test)  {
    return 0;
}

INT interrupt_configure(INT, INT, POINTER_T) {
    return 1;
}
/*-- Frontend Init -------------------------------------------------*/

INT frontend_init() {

  cm_msg(MINFO, "frontend_init() setup", "Test FE");

  odb settings = {
    {"Test", 123},
    {"sub", {}}
  };
  settings.connect_and_fix_structure("/Equipment/Test FE/Settings");
  // settings.watch(watch); <-- this works without segmentation fault

  odb new_settings("/Equipment/Test FE/Settings");
  new_settings.watch(watch); // <-- here I am getting a segmentation fault

  return CM_SUCCESS;
}

void watch(odb o) {
    std::string name = o.get_name();

    if (name == "Test") {
      printf("I am a watch on Test\n");
    }
}

/*-- Frontend Exit -------------------------------------------------*/

INT frontend_exit() {
  return CM_SUCCESS;
}

/*-- Frontend Loop -------------------------------------------------*/

INT frontend_loop() {
  return CM_SUCCESS;
}

/*-- Begin of Run --------------------------------------------------*/

INT begin_of_run(INT run_number, char *error) {
  return CM_SUCCESS;
}

/*-- End of Run ----------------------------------------------------*/

INT end_of_run(INT run_number, char *error) {
  return CM_SUCCESS;
}

/*-- Pause Run -----------------------------------------------------*/

INT pause_run(INT run_number, char *error) {
  return CM_SUCCESS;
}

/*-- Resume Run ----------------------------------------------------*/

INT resume_run(INT run_number, char *error) {
  return CM_SUCCESS;
}

/* -- Readout --*/
INT read_odb(char *pevent, INT){

    return 0;

}