"No appropriate default constructor" 我到处寻找答案
"No appropriate default constructor" I have looked everywhere for an answer
我已经查看了有关此主题的所有帖子，但没有一个有帮助。请帮助我的作业在两个小时后到期。
这是相关的标题
class RCB {
private:
str rID;
int numResources;
int availableResources;
int resourcesRequested; //The amount of resources requested including resources requested from PCB's in the waitlist
public:
std::list<PCB*> waitList;
RCB(str name, int r);
~RCB();
void setRID(str name) { rID = name; }
void allocateResources(int n) { availableResources -= n; }
void returnResources(int n) { availableResources += n; }
int getNumResources(){ return numResources; }
int getAvailableResources(){ return availableResources; }
str getRID(){ return rID; }
int getResourcesRequested() { return resourcesRequested; }
};
这是源文件
RCB::RCB(str name, int r) :
rID{ name },
numResources{ r },
availableResources{ r },
resourcesRequested{ 0 }
{}
我收到错误
错误1 错误 C2512："RCB"：没有可用的适当默认构造函数 C：\程序文件 （x86）\Microsoft Visual Studio 12.0\VC\include\tuple 746 1 进程调度程序
这是源的其余部分
#include "Data.h"
PCB::PCB(str name, int p) :
pID{ name },
status{ READY },
backptr{ nullptr },
parent{ nullptr },
priority{ p }
{
//Insert resource counters into the resource log
resourceLog.insert(std::pair<str, int>("R1", 0));
resourceLog.insert(std::pair<str, int>("R2", 0));
resourceLog.insert(std::pair<str, int>("R3", 0));
resourceLog.insert(std::pair<str, int>("R4", 0));
//Insert resource request counters into the request log
requestBackLog.insert(std::pair<str, int>("R1", 0));
requestBackLog.insert(std::pair<str, int>("R2", 0));
requestBackLog.insert(std::pair<str, int>("R3", 0));
requestBackLog.insert(std::pair<str, int>("R4", 0));
}
PCB::~PCB()
{
}
//Print the proccess ID to stdout
void PCB::printID()
{
std::cout << pID << " ";
}
RCB::RCB(str name, int r) :
rID{ name },
numResources{ r },
availableResources{ r },
resourcesRequested{ 0 }
{}
RCB::RCB(const RCB& r)
{
rID = r.rID;
numResources = r.numResources;
availableResources = r.availableResources;
resourcesRequested = r.resourcesRequested;
}
RCB::RCB() :
rID{ "R0" },
numResources{ 5 },
availableResources{ 5 },
resourcesRequested{ 0 }
{
}
MainProcess::MainProcess() :
initProcess("init", 0),
currentlyRunning{ &initProcess }
{
//Add init to the list of process names
nameList.push_back("init");
RCB R1("R1", 1);
RCB R2("R2", 2);
RCB R3("R3", 3);
RCB R4("R4", 4);
//Initialize four resources in the resource map
resourceMap.insert(std::pair<str, RCB>("R1", R1));
resourceMap.insert(std::pair<str, RCB>("R2", R2));
resourceMap.insert(std::pair<str, RCB>("R3", R3));
resourceMap.insert(std::pair<str, RCB>("R4", R4));
//Add a reference to the initial process to lowest list on the ready list
readyList[0].push_back(&initProcess);
initProcess.setStatus(RUNNING);
//Print the id of the init process to stdout
initProcess.printID();
}
void MainProcess::Release(str rID, int num)
{
//Check for negative numbers
if (num < 0){
std::cout << "error ";
return;
}
//Subtract resources from the resource log of the currently running process
currentlyRunning->resourceLog[rID] = std::max(currentlyRunning->resourceLog[rID] - num, 0);
//Add resources back to the available resources
resourceMap[rID].returnResources(num);
//Iterator pointing to the first PCB in the waitlist
std::list<PCB*>::iterator it = resourceMap[rID].waitList.begin();
//CONDITION
//The waitlist on the RCB is not empty AND
//the amount of available resources in the RCB is greater than the amount of
//requested resources by the PCB at the front of the waitlist
while (!resourceMap[rID].waitList.empty() && resourceMap[rID].getAvailableResources() > 0 && it != resourceMap[rID].waitList.end())
{
if ((*it)->requestBackLog[rID] <= resourceMap[rID].getAvailableResources() ){
//Allocate backloged resources from the RCB
resourceMap[rID].allocateResources((*it)->requestBackLog[rID]);
//Give the allocated resources to the PCB
(*it)->resourceLog[rID] += (*it)->requestBackLog[rID];
//Zero out the request back log
(*it)->requestBackLog[rID] = 0;
//Change the status of the PCB and add it to the ready list
(*it)->setStatus(READY);
(*it)->setBackPtr(readyList);
readyList[(*it)->getPriority()].push_back((*it));
//Move the iterator to the next element in the wait list
it++;
//Remove the PCB from the waitlist
resourceMap[rID].waitList.pop_front();
//Call the scheduler
Scheduler();
}
//If the PCB at the front of the wait list is asking for too many resources
//then just skip it and move on to the next PCB on the waitlist
else
{
it++;
}
}
}
void MainProcess::FreeResources(PCB* p)
{
//Free all the resources currently held by PCB p
for (auto& item : p->resourceLog){
Release(item.first, item.second);
}
}
void MainProcess::Destroy(str PID)
{
//Search the ready list for the PCB with the specified PID
for (int i = 1; i < 3; i++){
for (PCB* p : readyList[i]){
if (p->getPID() == PID){
KillTree(p);
Scheduler();
return;
}
}
}
//If no PCB was found with PID then output error
std::cout << "error ";
}
void MainProcess::KillTree(PCB* p)
{
//Recursively call kill tree on each child
if (!p->children.empty()){
for (PCB* child : p->children)
{
KillTree(child);
}
}
//If the PCB has no children then free all of its resources and delete it.
FreeResources(p);
delete p;
return;
}
void MainProcess::Create(str name, int p)
{
std::vector<str>::iterator it = std::find(nameList.begin(), nameList.end(), name);
if (it != nameList.end()){
std::cout << "error ";
return;
}
else{
//Add the new process name to the list of process names
nameList.push_back(name);
//Create a reference to a new process
PCB* newProcess = new PCB(name, p);
//Set the back pointer to the ready list
newProcess->setBackPtr(readyList);
//Set the parent pointer to the parent process
newProcess->setParent(currentlyRunning);
//Add it to the process tree
currentlyRunning->children.push_back(newProcess);
//Add the new process to the ready list
newProcess->setStatus(READY);
readyList[newProcess->getPriority()].push_back(newProcess);
//Call the scheduler
Scheduler();
}
}
void MainProcess::Request(str rID, int num)
{
RCB* rcb;
//Check for negative numbers
if (num < 0){
std::cout << "error ";
return;
}
//rcb is a reference to a resource in the resource map
rcb = &resourceMap[rID];
//If resources are available
if (rcb->getAvailableResources() >= num){
rcb->allocateResources(num);
//Give the requested resources to the running process
currentlyRunning->resourceLog[rID] += num;
//Insert RCB into resource list of currently running process if not in there already
std::list<RCB*>::iterator it = std::find(currentlyRunning->other_Resources.begin(), currentlyRunning->other_Resources.end(), rcb);
if (it == currentlyRunning->other_Resources.end()){
currentlyRunning->other_Resources.push_back(rcb);
}
}
else
{
//Stop the process from running and put it on the blocked list
currentlyRunning->setStatus(BLOCKED);
currentlyRunning->setBackPtr(&rcb->waitList);
readyList[currentlyRunning->getPriority()].pop_front();
rcb->waitList.push_back(currentlyRunning);
//Log the requested amount in the request back log
currentlyRunning->requestBackLog[rID] += num;
//Call Scheduler
Scheduler();
}
}
void MainProcess::Scheduler()
{
PCB* p = getHighestPriority();
if (currentlyRunning != p){
//Set the currently running process to the
currentlyRunning = p;
//Set the status of the currently running process to "RUNNING"
currentlyRunning->setStatus(RUNNING);
}
//Print the id of the currently running process
currentlyRunning->printID();
}
void MainProcess::TimeOut()
{
//Remove currently running process from the front of the list and put it in the back
readyList[currentlyRunning->getPriority()].pop_front();
currentlyRunning->setStatus(READY);
readyList[currentlyRunning->getPriority()].push_back(currentlyRunning);
Scheduler();
}
PCB* MainProcess::getHighestPriority()
{
//Iterate through the ready list to find the highest priority process
for (int i = 2; i >= 0; i--){
if (!readyList[i].empty()){
return readyList[i].front();
}
}
//Return null if no process is found
return nullptr;
}
void MainProcess::Reset()
{
for (PCB* p : initProcess.children){
KillTree(p);
}
Scheduler();
}
我很确定这就是问题所在
//Add init to the list of process names
nameList.push_back("init");
RCB R1("R1", 1);
RCB R2("R2", 2);
RCB R3("R3", 3);
RCB R4("R4", 4);
//Initialize four resources in the resource map
resourceMap.insert(std::pair<str, RCB>("R1", R1));
resourceMap.insert(std::pair<str, RCB>("R2", R2));
resourceMap.insert(std::pair<str, RCB>("R3", R3));
resourceMap.insert(std::pair<str, RCB>("R4", R4));
当您定义参数化构造函数 [RCB（str name， int r）] 时，编译器不会生成默认的无参数构造函数。因此，在您的情况下，如果您尝试创建 RCB [RCB obj;] 的对象，它势必会抛出此错误。要解决，您需要定义一个默认的无参数构造函数。不确定这是否有帮助。
根据错误，类 RCB 没有默认构造函数。这很好。并非所有类都必须具有默认构造函数。但是，代码中的某些内容使用 RCB（不是问题中包含的内容的一部分）正在尝试显式或隐式调用 RCB 的默认构造函数。
例如，如果您在代码中的某个位置声明
RCB rcb;
然后，您将使用默认构造函数。
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