Wt

cc->cellWasModified().connect(std::bind(&PlannerCalendar::calendarWasModified, this ));

std::bind fixed it for me, but why i got this error without bind ??

I have the same spec. Ubuntu 16.04 , gcc 5.4.1

// This may look like C code, but it's really -*- C++ -*-
/*
 * Copyright (C) 2010 Emweb bvba, Kessel-Lo, Belgium.
 *
 * See the LICENSE file for terms of use.
 */
#ifndef CALENDAR_CELL_H_
#define CALENDAR_CELL_H_

#include "UserAccount.h"

#include <Wt/WContainerWidget.h>

//debuging
#include <iostream>

using namespace Wt;

class CalendarCell : public WContainerWidget
{
public:
  CalendarCell();

  void update(const dbo::ptr<UserAccount>& user, const WDate& date);

  WDate date() {return date_; }
  dbo::ptr<UserAccount> user() { return user_; }

  Signal<WString>& cellWasModified() { std::cout << "from CalendarCell" << std::endl; return cellModified_;}; //hard coded
  Signal<WString> cellModified_;

private:
  WDate date_;
  dbo::ptr<UserAccount> user_;
  std::unique_ptr<WDialog> dialog_;

  void showEntryDialog();
  void showAllEntriesDialog();
};

#endif //CALENDAR_CELL_H_

/*
 * Copyright (C) 2010 Emweb bvba, Kessel-Lo, Belgium.
 *
 * See the LICENSE file for terms of use.
 */

#include "CalendarCell.h"
#include "EntryDialog.h"
#include "AllEntriesDialog.h"
#include "Login/PlannerApplication.h"
#include "Entry.h"

#include <Wt/WDate.h>
#include <Wt/WText.h>

#include <Wt/WSignal.h>

#include <string>


CalendarCell::CalendarCell()
  : WContainerWidget()
{
  resize(100, 120); // single cell size

  setStyleClass("cell");
  setToolTip(tr("calendar.cell.tooltip"));

  clicked().connect(this, &CalendarCell::showEntryDialog);
}

void CalendarCell::update(const dbo::ptr<UserAccount>& user, const WDate& date)
{
  date_ = date;
  user_ = user;
  //Signal
  std::cout << "edit from cell" << std::endl;
  cellModified_.emit(""); // hard coded for debugin
  //
  clear();

  dbo::Session& session = PlannerApplication::plannerApplication()->session;
  dbo::Transaction transaction(session);

  WString day;
  day += std::to_string(date.day());
  if (date.day() == 1)
  {
    day += " " + WDate::longMonthName(date.month());
  }
  auto header = cpp14::make_unique<WText>(day);
  header->setStyleClass("cell-header");
  addWidget(std::move(header));

  typedef dbo::collection< dbo::ptr<Entry> > Entries;
  Entries entries = user->entriesInRange(date, date.addDays(1));

  const unsigned maxEntries = 4;
  unsigned counter = 0;
  for (Entries::const_iterator i = entries.begin();
       i != entries.end(); ++i, ++counter) {
    if (counter == maxEntries) {
      auto extra =
        cpp14::make_unique<WText>(tr("calendar.cell.extra")
          .arg((int)(entries.size() - maxEntries)));
      auto extraPtr = addWidget(std::move(extra));
      extraPtr->setStyleClass("cell-extra");

      extraPtr->clicked().preventPropagation();
      extraPtr->clicked().connect(this, &CalendarCell::showAllEntriesDialog);
      break;
    }

    WString format = EntryDialog::timeFormat;
    auto textToCell = cpp14::make_unique<WText>(
            // I commented this out becase this app is not exact to hour day planer but rather
            // week planing app
            //(*i)->start.toString(format) +
            //"-" +
            //(*i)->stop.toString(format) +
            /*": " + */ (*i)->summary);


    //ADD color acording to status of task
    if((*i)->isFinished.empty())
    {
        textToCell->setStyleClass("unfinished-task");
    }
    else
    {
        textToCell->setStyleClass("finished-task");
    }

    addWidget(std::move(textToCell));

  }

  transaction.commit();
}

void CalendarCell::showEntryDialog()
{
  WString title =
    tr("calendar.entry.title").arg(date_.toString("ddd, d MMM yyyy"));

    dialog_ = cpp14::make_unique<EntryDialog>(title, this);
    dialog_->show();
}

void CalendarCell::showAllEntriesDialog()
{
  WString title =
    tr("calendar.cell.all-entries.title")
    .arg(date_.toString("ddd, d MMM yyyy"));

  dialog_ = cpp14::make_unique<AllEntriesDialog>(title, this);
  dialog_->show();
}

And this is the planner calendar class

// This may look like C code, but it's really -*- C++ -*-
/*
 * Copyright (C) 2010 Emweb bvba, Kessel-Lo, Belgium.
 *
 * See the LICENSE file for terms of use.
 */

#ifndef PLANNER_CALENDAR_H_
#define PLANNER_CALENDAR_H_

#include "UserAccount.h"

#include <Wt/Dbo/Dbo.h>
#include <Wt/WCalendar.h>
#include <Wt/WSignal.h>
#include <Wt/WDate.h>

using namespace Wt;

class PlannerCalendar : public WCalendar
{
public:
  PlannerCalendar(dbo::ptr<UserAccount> user);

  Signal<WString>& calendarWasModified() {return calendarModified_ ;} //TODO implement its now hard coded
  Signal<WString> calendarModified_;

  void onlyForDebuging() {std::cout << "Debug worked in PlannerCalendar" << std::endl; calendarModified_.emit("");}
protected:
  virtual WWidget* renderCell(WWidget* widget, const WDate& date) override;

private:
  dbo::ptr<UserAccount> user_;
};

#endif //PLANNER_CALENDAR_H_

And .cpp file

/*
 * Copyright (C) 2010 Emweb bvba, Kessel-Lo, Belgium.
 *
 * See the LICENSE file for terms of use.
 */

#include "PlannerCalendar.h"
#include "CalendarCell.h"
#include "Entry.h"
#include <Wt/WWidget.h>
#include <memory>

using namespace Wt;

PlannerCalendar::PlannerCalendar(dbo::ptr<UserAccount> user)
  : WCalendar(),
    user_(user)
{
  setStyleClass(styleClass() + " calendar");
  //setSelectionMode(SelectionMode::None);
}

WWidget* PlannerCalendar::renderCell(WWidget* widget, const WDate& date)
{
  if (!widget)
  {
    widget = new CalendarCell();
  }

  CalendarCell* cc = (CalendarCell*)widget;
  cc->update(user_, date);


  cc->cellWasModified().connect(this, &PlannerCalendar::calendarWasModified);
  cc->cellWasModified().connect(this ,&PlannerCalendar::onlyForDebuging);

  //calendarModified_.emit(WString("tom")); //TODO hardcoded
 // cc->cellWasModified().connect(this, &PlannerCalendar::calendarWasModified);
  return cc;
}

I dont know how to send multiple files so i post them here.