生成程序时出现此错误:Apple Mach-O Linker (ld) Error
Linker Command failed with exit code 1
。通常,当我尝试修复此错误时,其原因是具有主要功能的文件为#include
-将文件多次删除。但是,我不认为这次是这种情况。 X Code还向我通知了duplicate symbol _passed in:
ranker.o
和olympic.o
。
//competitor.h
#ifndef __Olympic_Lab__competitor__
#define __Olympic_Lab__competitor__
#include <iostream>
using namespace std;
class Competitor {
char* name = nullptr;
int laneAssignment;
float time;
public:
Competitor(char n[], int lane);
~Competitor();
void setTime(float f);
char* getName(){ return name; }
int getLane(){ return laneAssignment; }
float getTime(){ return time; }
void print(){ cout << name << endl; }
};
#endif
//competitor.cpp
#include "competitor.h"
Competitor::Competitor(char n[], int lane){
name = n;
laneAssignment = lane;
}
Competitor::~Competitor(){
//does nothing for now
}
void Competitor::setTime(float t){
time = t;
}
//ranker.h
#ifndef __Olym__ranker__
#define __Olym__ranker__
#include <vector>
#include "competitor.h"
using namespace std;
int passed = 0;
class Ranker {
bool boolean = true;
public:
vector<Competitor*> rv;
Ranker(int lanes);
~Ranker();
int addList(Competitor* c);
Competitor* getLane(int lane);
Competitor* getFinish(int finish);
int getFilled();
};
#endif
//ranker.cpp
#include "ranker.h"
Ranker::Ranker(int lan){
rv.resize(lan - 1);
for(int i = 0; i <= rv.size(); i++){
rv[i] = nullptr;
}
}
Ranker::~Ranker(){
for(int i = 0; i <= rv.size(); i++){
delete rv[i];
}
}
int Ranker::addList(Competitor *c){
if(c != NULL && passed <= 4){
rv[passed++] = c;
return passed - 1;
}
return 0;
}
Competitor* Ranker::getLane(int lane){
for(int i = 0; i <= rv.size(); i++){
if(rv[i]->getLane() == lane && rv[i] != NULL){
return rv[i];
}
}
return rv[0];
}
Competitor* Ranker::getFinish(int finish){
if(boolean){
Competitor *temp = nullptr;
int highestIndex;
for(int i = rv.size(); i >= 0; i--){
highestIndex = i;
for(int j = i; j >= 0; j--){
if(rv[j] != nullptr && rv[highestIndex] != nullptr){
if(rv[j]->getTime() > rv[highestIndex]->getTime())
highestIndex = j;
}
}
temp = rv[i];
rv[i] = rv[highestIndex];
rv[highestIndex] = temp;
}
delete temp;
temp = *new Competitor*;
boolean = false;
}
return rv[finish - 1];
}
int Ranker::getFilled(){
int filled = 0;
for(int i = 0; i <= rv.size(); i++){
if(rv[i] != NULL){
filled++;
}
}
return filled;
}
//olympic.h
#ifndef _Olympic_Lab__olympic__
#define _Olympic_Lab__olympic__
#include "ranker.h"
#endif
//olympic.cpp
#include "olympic.h"
int main(){
const int lanes = 4;
Ranker rank(lanes);
Competitor* starters[4];
starters[0] = new Competitor("EmmyLou Harris", 1);
starters[1] = new Competitor("Nanci Griffith", 2);
starters[2] = new Competitor("Bonnie Raitt", 3);
starters[3] = new Competitor("Joni Mitchell", 4);
starters[0]->setTime((float)12.0);
starters[1]->setTime((float)12.8);
starters[2]->setTime((float)11.0);
starters[3]->setTime((float)10.3);
for(int i = 0; i < lanes; i++){
rank.addList(starters[i]);
}
cout << "Competitors by lane are:" << endl;
for(int i = 1; i <= lanes; i++)
rank.getLane(i)->print();
cout << "Rankings by finish are:" << endl;
for(int i = 1; i <= lanes; i++)
rank.getFinish(i)->print();
for(int i = 0; i < lanes; i++){
delete starters[i];
}
}
如果有人可以协助我准确找到导致此错误的信息,我们将不胜感激。谢谢!
最佳答案
如果您在 header 中声明变量,它将在每个包含 header 的文件中重复。
因此,ranker.h中的int passed = 0;
将给您带来很多痛苦。 ranker和olympian都分配了不同的passed
,链接器现在不知道哪个是真正传递的。
所以你可能想要的是
extern int passed;
在ranker.h中声明已通过将在某个时候存在(如果尚不存在),因此不需要分配。编译器将愉快地进行并允许您使用
passed
。然后在ranker.cpp中声明
int passed = 0;
分配
passed
并满足链接器的要求。现在,您只有一个passed
,任何包含ranker.h的人都可以查看和使用它。如果您需要多个
passed
,则必须做其他事情,以使它们不具有相同的名称和范围,但这似乎与您的目标不符。离题:抵制将
using namespace std;
放在头文件中的冲动。这可能会导致将来出现难以调试的问题。更多内容:Why is "using namespace std" considered bad practice?关于c++ - 为什么我的代码有一个 “Apple Mach-O Linker Error?”,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/38711521/