Question

i have the following method :

string Company::cheap(list<Candidate*>& candidates) {
    candidates.sort(candidateSalaryCompare);
    for (std::list<Candidate*>::iterator iter = candidates.begin(); iter
    != candidates.end(); ++iter) {
    }
    int m(candidates.front()->getExpectedSalary());
    list<Candidate*> potentialList;
    for (std::list<Candidate*>::iterator iter = candidates.begin(); (*iter)->getExpectedSalary()
    == m && iter != candidates.end(); ++iter)
        potentialList.push_back(*iter);
    if (potentialList.size() > 0)
        potentialList.sort(candidateIdCompare);
    return potentialList.front()->getId();
}

running it as is and my program works, but if i remove the empty FOR loop in the beginning (which doesn’t do anything) i get a segmentation fault.
any clues ?

EDIT

candidate class, and actually i’m not sure at what line i’m getting the segfault,
i’m using eclipse and the debugger doesn’t seem to work

#include "../include/Candidate.h"
#include <iostream>
#include "../include/AppLogger.h"
#include <sstream>

Candidate::Candidate(string id, list<Skill> skills, list<
        string> desiredJobs, double expectedSalary) :
        id_(id), dateJoined_(), skills_(skills),
        desiredJobs_(desiredJobs), expectedSalary_(expectedSalary),
        originalSalary_(expectedSalary), gotJob_(0) {
}


void Candidate::compromise(const DateTime& currentDate) {
    double salaryAfter30(0.9*this->originalSalary_);
    double salaryAfter60(0.8*this->originalSalary_);
    double salaryAfter90(0.7*this->originalSalary_);
    Timespan duration = currentDate - this->dateJoined_;
    if (duration.days() == 30 || duration.days() == 60 || duration.days() == 90) {
        if (duration.days() == 30 && (this->expectedSalary_
                == this->originalSalary_)) {
            this->expectedSalary_ = salaryAfter30;
            std::stringstream sstm;
            sstm << "Candidate "<< this->getId() <<" is willing to compromise, and his expected salary is " <<this->expectedSalary_ << ".";
            CAppLogger::Instance().Log(sstm.str(),
                    Poco::Message::PRIO_WARNING);
            return;
        }
        else if (duration.days()==30)
            poco_bugcheck_msg("Error, 30 days passed, worker already compromised");
        if (duration.days() == 60 && (this->expectedSalary_ == salaryAfter30)) {
            this->expectedSalary_ = salaryAfter60;
            std::stringstream sstm;

            sstm << "Candidate "<< this->getId() <<" is willing to compromise, and his expected salary is " <<this->expectedSalary_ << ".";
            CAppLogger::Instance().Log(sstm.str(),
                    Poco::Message::PRIO_WARNING);
            return;
        }
        else if (duration.days()==60)
            poco_bugcheck_msg("Error, 60 days passed, worker already compromised");

        if ((duration.days() == 90) && (this->expectedSalary_ == salaryAfter60)) {
            this->expectedSalary_ = salaryAfter90;
            std::stringstream sstm;
            sstm << "Candidate "<< this->getId() <<" is willing to compromise, and his expected salary is " <<this->expectedSalary_ << ".";
            CAppLogger::Instance().Log(sstm.str(),
                    Poco::Message::PRIO_WARNING);
            return;
        }
        else if (duration.days()==90)
            poco_bugcheck_msg("Error, 90 days passed, worker already compromised");

    }
    else poco_bugcheck_msg("Error, worker told to compromise when not needed");


}

list<Skill> Candidate::getSkills() const {
    return this->skills_;
}

list<string> Candidate::getDesiredJobs() const {
    return this->desiredJobs_;

}
double Candidate::getExpectedSalary() const {
    return this->expectedSalary_;
}
DateTime Candidate::getDateJoined() const {
    return this->dateJoined_;
}
DateTime Candidate::getDateLeft() const {
    return this->dateLeft_;
}
void Candidate::setDateLeft(const DateTime& date) {
    this->dateLeft_ = date;
}
string Candidate::getId() const {
    return this->id_;
}

void Candidate::setDateJoined(const DateTime& date) {
    this->dateJoined_=date;
    this->setGotJob();
}

void Candidate::setGotJob() {
    if (this->gotJob_==1)
        std::cerr<<"error, setting gotJob while already has job"<<std::endl;
    this->gotJob_=1;
}
bool Candidate::gotJob() const {
    return this->gotJob_;
}
void Candidate::setQl(double ql){
        jobQl_=ql;
}

int Candidate::getQl() const{
    return this->jobQl_;
}

after applying the supplied solutions i get the following error :

assignment2(48823) malloc: *** mmap(size=140734799806464) failed (error code=12)
*** error: can't allocate region
*** set a breakpoint in malloc_error_break to debug
terminate called after throwing an instance of 'std::bad_alloc'
  what():  std::bad_alloc

EDIT

changed int m to double m and now it seems to work
because get expected salary returns a double
but why did it cause that error ?

Answer 1

Please, look at Cris Hopman answer here, as his answer is much more complete and detailed than mine pointing to other issues that can/will cause undefined behavior (segmentation fault) in the original code.

This condition is wrong:

for (std::list<Candidate*>::iterator iter = candidates.begin(); (*iter)->getExpectedSalary()
== m && iter != candidates.end(); ++iter)

You should reorder so that the test for end() comes before the dereference and keep the short circuit evaluation. As it is, you are dereferencing a pointer past the end of the container:

for (std::list<Candidate*>::iterator iter = candidates.begin(); 
     iter != candidates.end() && (*iter)->getExpectedSalary() == m; ++iter)