为什么链表中的数据在嵌套函数中会更改/损坏?

我正在为离散时间CPU调度模拟器编写代码。它只是生成流程并相应地安排它们。我目前正在实施FCFS时间表。我了解离散时间模拟器的性质，但我在C++中实现时遇到了麻烦。

问题发生在handleNextEvent()和generateProcessDeparture()之间的跳转中。在某些时候，链接列表事件队列中的数据会损坏。(eventQueue.cpp267行)

这个想法是handleNextEvent()从事件队列中提取下一个事件，即到达(类型 1)，从而为同一进程(PID 1)生成离开(类型 2)。到目前为止，一切都很好。

一旦控制权被generateProcessDeparture()释放并返回到handleNextEvent()，原始到达事件将被删除，该事件应仅保留离开事件。

相反，我有狼吞虎咽的傻瓜 - 不知何故加上到达事件的额外副本。 我已经研究了范围和指针，但我是C++新手，找不到我做错了什么。

任何见解都值得赞赏。谢谢。

事件队列.cpp

/*
EVENT TYPES
-1  HEAD: There can be only one head in the linked list of events.
0 NEW: If 0 the event is new and blank.  For error checking.
1 arrival:  Indicates arrival of a single process.
2 departure:  Indicates completion of process.  If the event exists within
the event queue, then the simulator has NOT YET accounted for it in 
system state or metric report.
*/
#include "eventQueue.h"
#include <iostream>
eventQueue::eventQueue(int dac, int aar, float ast, float q){
// Initiatialize head of event linked list.
eHeadPtr = new event;
eHeadPtr->type = -1;
eHeadPtr->time = -1;
eHeadPtr->next = NULL;
rqHeadPtr = new event;
rqHeadPtr->type = -1;
rqHeadPtr->time = -1;
rqHeadPtr->next = NULL;
defaultArrivalCount = dac;
averageArrivalRate = aar;
averageServiceTime = ast;
averageServiceRate = 1 / ast;
quantum = q;
}
void eventQueue::runFCFS(){
std::cout << "nnrunFCFS()...";
/*  generateProcessArrival();
generateProcessArrival();
generateProcessArrival();
generateProcessArrival();
generateProcessArrival();
generateProcessDeparture(*eHeadPtr->next);*/
while(handledProcessCount < defaultArrivalCount){
std::cout << "nnCurrent event queue: ";
printEventQueue();
std::cout << "nCurrent ready queue: ";
printReadyQueue();
std::cout << "nLatestArrivalTime: " << latestArrivalTime;
std::cout << "nNextDepartureTime: " << nextDepartureTime;

if(eventQueueEmpty()){
generateProcessArrival();
}
handleNextEvent();
//std::cout << "nnEvent queue after handleNextEvent:";
//printEventQueue();
while(latestArrivalTime <= nextDepartureTime){
std::cout << "nLatestArrivalTime( " << latestArrivalTime << " ) <= nextDepartureTime( " << nextDepartureTime << " )";
generateProcessArrival();
}
}
}
bool eventQueue::eventQueueEmpty(){
if (eHeadPtr->next == NULL){
return true;
}
return false;
}
bool eventQueue::readyQueueEmpty(){
if (rqHeadPtr->next == NULL){
return true;
}
return false;
}
void eventQueue::printEvent(event e){
std::cout << "n  [ TYPE: " << e.type << ", TIME: " << e.time << ", PID: "
<< e.proc.id << ", BURST: " << e.proc.cpuBurst << ", A_TIME: " << 
e.proc.arrTime << ", S_TIME: "  << e.proc.servTime << ", R_TIME: " << 
e.proc.remTime << ", NEXT: " << e.next << " ] ";
return;
}
void eventQueue::printEventQueue(){
if (eventQueueEmpty()){
std::cout << "n  [ ]";
}
else{
event* tmpPtr = eHeadPtr;
do{
tmpPtr = tmpPtr->next;
printEvent(*tmpPtr);
}while(tmpPtr->next != NULL);
tmpPtr = NULL;
return;
}
}
void eventQueue::printReadyQueue(){
if (readyQueueEmpty()){
std::cout << "n  [ ]";
}
else{
event* tmpPtr = eHeadPtr;
do{
tmpPtr = tmpPtr->next;
printEvent(*tmpPtr);
}while(tmpPtr->next != NULL);
tmpPtr = NULL;
return;
}
}
double eventQueue::generateBurst(){
int intRand = rand() % 100;
float realRand = intRand / 100.0;
double burst = ((-log(1 - realRand))/averageServiceRate);
return burst;
}
double eventQueue::generateArrivalDiff(){
double diffTime;
int intRand = rand() % 100; 
double realRand = intRand / 100.0;
double dTime = ((-log(1 - realRand)/averageArrivalRate));
return dTime;
}
void eventQueue::generateProcessArrival(){
std::cout << "nngenerateProcessArrival()...";
// Establish pointers.
event* frontPtr = new event;
event* backPtr = new event;
event* newPtr = new event;
double burst = generateBurst();
double arrivalDiff = generateArrivalDiff();
latestArrivalTime += arrivalDiff;
newProcessID++;
newPtr->type = 1;
newPtr->time = latestArrivalTime;
newPtr->proc.id = newProcessID;
newPtr->proc.arrTime = latestArrivalTime;
newPtr->proc.cpuBurst = burst;
newPtr->proc.servTime = 0;
newPtr->proc.remTime = burst;
std::cout << "nCreated new arrival event:";
printEvent(*newPtr);
if(eventQueueEmpty()){
eHeadPtr->next = newPtr;
std::cout << "nEvent queue was empty.  Added new arrival event to queue:";
printEventQueue();
}
else{
backPtr = eHeadPtr;
frontPtr = eHeadPtr->next;
while((newPtr->time > frontPtr->time) && (frontPtr->next != NULL)){
backPtr = frontPtr;
frontPtr = frontPtr->next;
}
if ((frontPtr->next == NULL)&&(newPtr->time > frontPtr->time)){
frontPtr->next = newPtr;
std::cout << "nAdded new arrival to end of event queue:";
printEventQueue();      
}
else{
backPtr->next = newPtr;
newPtr->next = frontPtr;
std::cout << "nAdded new arrival to (center/front) of event queue.";
printEventQueue();  
}
}
frontPtr = NULL;
backPtr = NULL;
newPtr = NULL;
return;
}
void eventQueue::generateProcessDeparture(event arr){
std::cout << "nngenerateProcessDeparture()...";
// Establish pointers.
event* frontPtr = new event;
event* backPtr = new event;
event* newPtr = new event;
// Generate departure based on arrival event.
event dep;
dep.type = 2;
dep.proc = arr.proc;
dep.time = arr.proc.arrTime + arr.proc.cpuBurst;
newPtr = &dep;
std::cout << "nCreated new departure event:";
printEvent(*newPtr);
if(eventQueueEmpty()){
eHeadPtr->next = newPtr;
std::cout << "nEvent queue was empty.  Added new arrival event to queue:";
printEventQueue();
}
else{
backPtr = eHeadPtr;
frontPtr = eHeadPtr->next;
while((newPtr->time > frontPtr->time) && (frontPtr->next != NULL)){
backPtr = frontPtr;
frontPtr = frontPtr->next;
}
if ((frontPtr->next == NULL)&&(newPtr->time > frontPtr->time)){
frontPtr->next = newPtr;
std::cout << "nAdded new arrival to end of event queue:";
printEventQueue();      
}
else{
backPtr->next = newPtr;
newPtr->next = frontPtr;
std::cout << "nAdded new arrival to (center/front) of event queue.";
printEventQueue();  
}
}
std::cout << "ngenerateProcessDeparture final check:";
printEventQueue();  
frontPtr = NULL;
backPtr = NULL;
newPtr = NULL;
return;
}
void eventQueue::handleNextEvent(){
std::cout << "nnhandleNextEvent()...";
// Establish pointers.
event* frontPtr = new event;
event* backPtr = new event; 
frontPtr = eHeadPtr->next;
backPtr = eHeadPtr;
systemClock = frontPtr->time;
if (frontPtr->type == 1){
std::cout << "nArrival event next.";
printEventQueue();
//printEvent(*frontPtr);
if (readyQueueEmpty() && cpuIdle){
std::cout << "nReady queue empty and cpu idle.";
generateProcessDeparture(*frontPtr);
printEventQueue();      
backPtr->next = frontPtr->next;     // Remove event from event queue.
std::cout << "nnreturn to handleNextEvent()...";
cpuIdle = false;
std::cout << "ncpuIdle: " << cpuIdle;
std::cout << "nCurrent event queue:";
printEventQueue();          
}
else{
std::cout << "nReady queue not empty and/or cpu not idle.";
pushReadyQueue(*frontPtr);
backPtr->next = frontPtr->next;
}
}
else if (frontPtr->type == 2){
std::cout << "nDeparture event next.";
printEvent(*frontPtr);
if (!readyQueueEmpty()){
std::cout << "nReady not empty.  Loading next event to CPU.";
event* tmpPtr = rqHeadPtr->next;    //Set tmpPtr to first item in readyQueue.
generateProcessDeparture(*tmpPtr);  //Creature departure event.
rqHeadPtr->next = tmpPtr->next;     //Delete old event.
tmpPtr = NULL;                      
}
else{
std::cout << "nReady queue empty and cpu idle.";
cpuIdle = true;
backPtr->next = frontPtr->next;
}
}
else{
std::cout << "nERROR: bad event type in event queue.";
}
handledProcessCount++;
frontPtr = NULL;
backPtr = NULL; 
return;
}
void eventQueue::pushReadyQueue(event e){
// Establish pointers.
event* frontPtr = new event;
event* backPtr = new event; 
while((e.time > frontPtr->time) && (frontPtr->next != NULL)){
backPtr = frontPtr;
frontPtr = frontPtr->next;
}
if ((frontPtr->next == NULL) && (e.time > frontPtr->time)){
frontPtr->next = &e;
std::cout << "nnAdded new arrival to end of ready queue:";
printReadyQueue();      
}
else{
backPtr->next = &e;
e.next = frontPtr;
std::cout << "nnAdded new arrival to (center/front) of ready queue.";
printReadyQueue();  
}
frontPtr = NULL;
backPtr = NULL; 
return; 
}

eventQueue.h

/*
EVENT TYPES
-1  INVALID: if 0 the event is new and blank.  For error checking.
0 head: There can be only one head in the linked list of events.
1 arrival:  Indicates arrival of a single process.
2 departure:  Indicates completion of process.  If the event exists within
the event queue, then the simulator has NOT YET accounted for it in 
system state or metric report.
*/
#ifndef EVENTQUEUE_H
#define EVENTQUEUE_H
# include <cstddef>
# include <tgmath.h>
# include <ctime>
struct process{
int id = -1;
double arrTime = -1;
double cpuBurst = -1;
double servTime = -1;
double remTime = -1;
};
struct event{
int type = -1;
double time = -1;
process proc;
event* next = NULL;
};
class eventQueue{
private:
event* eHeadPtr;
event* rqHeadPtr;
int defaultArrivalCount;
int handledProcessCount = 0;
int newProcessID = 0;
int averageArrivalRate;  // lambda
float averageServiceTime;   // Ts
float averageServiceRate;   // mu
float quantum;  //q
double latestArrivalTime = 0;
double nextDepartureTime = 0;
bool cpuIdle = true;
double systemClock = 0;
public:
eventQueue(const int, int, float, float);
void runFCFS();
bool eventQueueEmpty();
bool readyQueueEmpty();
void printEvent(event);
void printEventQueue();
void printReadyQueue();
void generateProcessArrival();
double generateBurst();
double generateArrivalDiff();
void generateProcessDeparture(event);
void handleNextEvent();
void pushReadyQueue(event);
};
#endif // EVENTQUEUE_H

主.cpp

/*
EVENT TYPES
0  INVALID: if -1 the event is new and blank.  For error checking.
1 head: There can be only one head in the linked list of events.
2 arrival:  Indicates arrival of a single process.
3 departure:  Indicates completion of process.  If the event exists within
the event queue, then the simulator has NOT YET accounted for it in 
system state or metric report.
*/
#include <iostream>
#include <tgmath.h>
#include "eventQueue.h"
void testInput(int, char*);
int main(int argc, char *argv[]){
srand(time(NULL));
char divider[] = "----------------------------------------------------------------------------------------------------------------";
const int DEF_ARR_COUNT= 10;
std::cout << "n" << divider;
std::cout << "nWelcome to the Simulator";
//TEST CMD LINE INPUT
testInput(argc, *argv);
// Setup environment and first default events (arrivals).
//int lambda = std::stoi(argv[2]);
//float Ts = std::stof(argv[3]);
//eventQueue eq(TOTAL_PR, lambda, Ts);
//eq.initDefaultArr();
//eq.printQueue(15);
eventQueue eq(DEF_ARR_COUNT, std::stoi(argv[2]), std::stof(argv[3]), std::stof(argv[4]));
eq.runFCFS();
//eq.printWithoutCount();

std::cout << "n" << divider;
std::cout << "nn";
return 0;
}
void testInput(int argc, char* argv){
if ((argc < 5) || ((argv[1] > 4) && (argv[1] < 1))){
std::cout << "nnERROR: invalid commandline input";
std::cout << "ntCommand line: <scheduler> <lambda> <Ts> <quantum>";
std::cout << "ntScheduler: [1,FCFS], [2, SRTF], [3, HRRN], [4, RR]";
std::cout << "ntExample: ./main 2 15 0.06 0.01";
}
}

这是我得到的一些示例输出：

anne@laptop:~/Dropbox/College/Current/Opsy/ROUND_4$ g++ main.cpp eventQueue.cpp -o main
anne@laptop:~/Dropbox/College/Current/Opsy/ROUND_4$ ./main 1 10 0.05 0.01
----------------------------------------------------------------------------------------------------------------
Welcome to the Simulator
runFCFS()...
Current event queue: 
[ ]
Current ready queue: 
[ ]
LatestArrivalTime: 0
NextDepartureTime: 0
generateProcessArrival()...
Created new arrival event:
[ TYPE: 1, TIME: 0.350656, PID: 1, BURST: 0.00871767, A_TIME: 0.350656, S_TIME: 0, R_TIME: 0.00871767, NEXT: 0 ] 
Event queue was empty.  Added new arrival event to queue:
[ TYPE: 1, TIME: 0.350656, PID: 1, BURST: 0.00871767, A_TIME: 0.350656, S_TIME: 0, R_TIME: 0.00871767, NEXT: 0 ] 
handleNextEvent()...
Arrival event next.
[ TYPE: 1, TIME: 0.350656, PID: 1, BURST: 0.00871767, A_TIME: 0.350656, S_TIME: 0, R_TIME: 0.00871767, NEXT: 0 ] 
Ready queue empty and cpu idle.
generateProcessDeparture()...
Created new departure event:
[ TYPE: 2, TIME: 0.359373, PID: 1, BURST: 0.00871767, A_TIME: 0.350656, S_TIME: 0, R_TIME: 0.00871767, NEXT: 0 ] 
Added new arrival to end of event queue:
[ TYPE: 1, TIME: 0.350656, PID: 1, BURST: 0.00871767, A_TIME: 0.350656, S_TIME: 0, R_TIME: 0.00871767, NEXT: 0x7fff5cc50520 ] 
[ TYPE: 2, TIME: 0.359373, PID: 1, BURST: 0.00871767, A_TIME: 0.350656, S_TIME: 0, R_TIME: 0.00871767, NEXT: 0 ] 
generateProcessDeparture final check:
[ TYPE: 1, TIME: 0.350656, PID: 1, BURST: 0.00871767, A_TIME: 0.350656, S_TIME: 0, R_TIME: 0.00871767, NEXT: 0x7fff5cc50520 ] 
[ TYPE: 2, TIME: 0.359373, PID: 1, BURST: 0.00871767, A_TIME: 0.350656, S_TIME: 0, R_TIME: 0.00871767, NEXT: 0 ] 
[ TYPE: 1, TIME: 0.350656, PID: 1, BURST: 0.00871767, A_TIME: 0.350656, S_TIME: 0, R_TIME: 0.00871767, NEXT: 0x7fff5cc50520 ] 
[ TYPE: 1556416656, TIME: 4.6627e-310, PID: 1556415824, BURST: 0.00871767, A_TIME: 4.6627e-310, S_TIME: 6.95322e-310, R_TIME: 6.95322e-310, NEXT: 0x55d52b320ec1 ] 
Segmentation fault (core dumped)

根据我对分段错误的理解，它通常是由于引用数组或列表越界？