我正在为一个类项目编写代码，我在Xcode中完成了所有工作。我能够在Xcode中编译w /参数并获得输出。但是，当我尝试在终端中编译它时，我不断收到此错误（我也不确定我是否正确编译它）：
francis-mbp:CS280-Assignment1 fren$ gcc /Users/fren/Desktop/CS280-Assignment1/main.cpp -o main
/Users/fren/Desktop/CS280-Assignment1/main.cpp:31:32: warning: in-class initialization of non-static data member is a C++11 extension [-Wc++11-extensions]
list<string>::iterator iter=lineToPrint.begin();
^
/Users/fren/Desktop/CS280-Assignment1/main.cpp:32:19: warning: in-class initialization of non-static data member is a C++11 extension [-Wc++11-extensions]
int charLimit = 60;
^
2 warnings generated.
Undefined symbols for architecture x86_64:
"std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::compare(char const*) const", referenced from:
_main in main-b9d962.o
"std::__1::locale::has_facet(std::__1::locale::id&) const", referenced from:
std::__1::basic_filebuf<char, std::__1::char_traits<char> >::basic_filebuf() in main-b9d962.o
"std::__1::locale::use_facet(std::__1::locale::id&) const", referenced from:
std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::endl<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) in main-b9d962.o
std::__1::basic_filebuf<char, std::__1::char_traits<char> >::imbue(std::__1::locale const&) in main-b9d962.o
std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in main-b9d962.o
std::__1::basic_filebuf<char, std::__1::char_traits<char> >::basic_filebuf() in main-b9d962.o
"std::__1::ios_base::getloc() const", referenced from:
std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::endl<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&) in main-b9d962.o
std::__1::basic_ostream<char, std::__1::char_traits<char> >& std::__1::__put_character_sequence<char, std::__1::char_traits<char> >(std::__1::basic_ostream<char, std::__1::char_traits<char> >&, char const*, unsigned long) in main-b9d962.o
"std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::erase(unsigned long, unsigned long)", referenced from:
Line::addWord(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >) in main-b9d962.o
"std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::__init(char const*, unsigned long)", referenced from:
Line::addWord(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >) in main-b9d962.o
Line::printLine(int) in main-b9d962.o
_main in main-b9d962.o
"std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::__init(char const*, unsigned long, unsigned long)", referenced from:
std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > std::__1::operator+<char, std::__1::char_traits<char>, std::__1::allocator<char> >(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, char const*) in main-b9d962.o
"std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::__init(unsigned long, char)", referenced from:
std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> > std::__1::__pad_and_output<char, std::__1::char_traits<char> >(std::__1::ostreambuf_iterator<char, std::__1::char_traits<char> >, char const*, char const*, char const*, std::__1::ios_base&, char) in main-b9d962.o
"std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::append(char const*, unsigned long)", referenced from:
std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > std::__1::operator+<char, std::__1::char_traits<char>, std::__1::allocator<char> >(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, char const*) in main-b9d962.o
"std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::assign(char const*)", referenced from:
Line::addWord(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >) in main-b9d962.o
_main in main-b9d962.o
"std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::push_back(char)", referenced from:
_main in main-b9d962.o
"std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::basic_string(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&)", referenced from:
Line::addWord(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >) in main-b9d962.o
std::__1::list<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > >::push_back(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in main-b9d962.o
std::__1::list<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > >::insert(std::__1::__list_const_iterator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, void*>, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in main-b9d962.o
Line::checkBack() in main-b9d962.o
_main in main-b9d962.o
"std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::basic_string(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, unsigned long, unsigned long, std::__1::allocator<char> const&)", referenced from:
Line::addWord(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >) in main-b9d962.o
"std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::~basic_string()", referenced from:
Line::addWord(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >) in main-b9d962.o
std::__1::list<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > >::pop_back() in main-b9d962.o
std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > std::__1::operator+<char, std::__1::char_traits<char>, std::__1::allocator<char> >(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, char const*) in main-b9d962.o
Line::printLine(int) in main-b9d962.o
std::__1::list<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > >::pop_front() in main-b9d962.o
std::__1::list<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > >::push_back(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in main-b9d962.o
std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > std::__1::operator+<char, std::__1::char_traits<char>, std::__1::allocator<char> >(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, char const*) in main-b9d962.o
std::__1::list<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > >::insert(std::__1::__list_const_iterator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, void*>, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in main-b9d962.o
Line::printLine(int) in main-b9d962.o
Line::popBack(int) in main-b9d962.o
...
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
francis-mbp:CS280-Assignment1 fren$
这是我项目的代码（不包括字符限制的主要bc）：
#include <iostream>
#include<string>
#include<vector>
#include<sstream>
#include<fstream>
#include<algorithm>
#include<queue>
#include<list>
#include<iterator>
#include<ctype.h>
using namespace std;
/*
Class defining data structure that holds linked list containing words to be output
Contains words on a per-line basis (Empties after each line is printed)
Handles list operations
*/
class Line
{
public:
list<string> lineToPrint;
list<string>::iterator iter=lineToPrint.begin();
int charLimit = 60;
string spaceToInsert;
int totalChars;
int totalSpaces;
int numWords;
int placesForSpaces;
int spacePerPlace;
int extraSpaces;
void addWord (string word);
void reset (void);
void changeLimit (int newLimit);
void printLine (int endOfParagraph);
void calculateSpaces(void);
void newParagraph(void);
void popBack(int type);
string checkBack(void);
};
void Line::addWord(string word) {
cout << "adding word: " << word << endl;
string firstHalfWord;
string secondHalfWord;
int numToTruncate;
int splittingWord = 1;
lineToPrint.push_back(word);
totalChars += word.length();
numWords ++;
calculateSpaces();
if(((totalChars > charLimit) && (numWords >= 1)) || ((totalSpaces < placesForSpaces) && (spacePerPlace == 0))) {
splittingWord = 0;
lineToPrint.pop_back();
numToTruncate = totalChars - (charLimit - placesForSpaces - 1);
if(numToTruncate > word.length()) {
cout << numToTruncate << " " << word.length();
cout << "error" << endl;
} else {
secondHalfWord = word.substr(word.length() - numToTruncate);
firstHalfWord = word.erase(word.length() - numToTruncate) + "-";
}
lineToPrint.push_back(firstHalfWord);
totalChars -= (word.length() + secondHalfWord.length());
totalChars += firstHalfWord.length();
calculateSpaces();
}
if((spacePerPlace <= 2 && extraSpaces<= placesForSpaces)||(spacePerPlace == 3 && extraSpaces == 0)) {
if(spacePerPlace == 1){
spaceToInsert = " ";
} else if (spacePerPlace == 2) {
spaceToInsert = " ";
} else if (spacePerPlace == 3) {
spaceToInsert = " ";
}
iter++;
for(int j = placesForSpaces; j > 0; j--) {
//cout << "inserting " << spacePerPlace << " spaces!" << endl;
lineToPrint.insert(iter, spaceToInsert);
totalSpaces -= spacePerPlace;
if(extraSpaces != 0){
lineToPrint.insert(iter, " ");
totalSpaces --;
extraSpaces --;
}
iter++;
}
printLine(1);
}
if(splittingWord == 0 && secondHalfWord.length() > charLimit){
iter = lineToPrint.begin();
addWord(secondHalfWord);
} else if (splittingWord == 0 && secondHalfWord.length() <= charLimit) {
lineToPrint.push_back(secondHalfWord);
totalChars += secondHalfWord.length();
numWords ++;
}
iter = lineToPrint.begin();
splittingWord = 1;
}
//Resets the list and variables for calculating spaces to insert
void Line::reset(void) {
lineToPrint.clear();
totalChars = 0; totalSpaces = 0; numWords = 0; placesForSpaces = 0;
}
//Changes the variable limit used in space insert calculations
void Line::changeLimit(int newLimit) {
//cout << "Changing Limit to: " << newLimit << endl;
charLimit = newLimit;
}
//Makes calculations for variables used in space insertion calculations
void Line::calculateSpaces(void) {
//cout << "calculating spaces..." << endl;
totalSpaces = charLimit - totalChars;
if (numWords == 1 && totalChars >= charLimit) {
placesForSpaces = 0;
spacePerPlace = 0;
} else {
if(numWords == 1){
placesForSpaces = 1;
} else {
placesForSpaces = numWords - 1;
}
spacePerPlace = totalSpaces/placesForSpaces;
extraSpaces = totalSpaces%placesForSpaces;
}
//cout << "totalChars: "<< totalChars <<" totalSpaces: "<< totalSpaces << " numWOrds: " << numWords << " placesFOrSpaces: " << placesForSpaces << " spacePerPlace: " << spacePerPlace << " extraSpaces: " << extraSpaces << endl;
}
//Prints the list (with spaces included)
//Takes int argument; 0 = end of paragraph, 1 = not end of paragraph
void Line::printLine(int endOfParagraph) {
//p1cout << "character limit: " << charLimit << endl;
if(endOfParagraph == 1) {
cout << "printing line NOT end of paragraph" << endl;
for(list<string>::iterator it = lineToPrint.begin(); it != lineToPrint.end(); it++){
cout << *it;
lineToPrint.pop_front();
}
} else if (endOfParagraph == 0) {
iter++;
cout << "printing line end of paragraph" << endl;
if (numWords != 1) {
for(int i = placesForSpaces; i >0; i--) {
lineToPrint.insert(iter, " ");
iter++;
}
}
iter = lineToPrint.begin();
for(list<string>::iterator it = lineToPrint.begin(); it != lineToPrint.end(); it++){
cout << *it;
lineToPrint.pop_front();
}
}
cout << endl;
totalChars = 0; totalSpaces = 0; numWords = 0; placesForSpaces = 0;
}
//Prints a new line to separate paragraphs
void Line::newParagraph(void){
cout << endl;
}
//Returns the string held in the back of the list
string Line::checkBack(void) {
return lineToPrint.back();
}
//Removes a string off the back of the list
void Line::popBack(int type) {
if(type == 1){
string wordToPop = checkBack();
cout << "word to pop : " << wordToPop << endl;
int length = wordToPop.length();
cout << "length of w2pop : " << length <<endl;
totalChars -= length;
}
//cout << "popping from back: " << checkBack();
lineToPrint.pop_back();
numWords --;
}
感谢您的帮助
答案 0 :(得分：2)
将编译器命令行更改为
g++ /Users/fren/Desktop/CS280-Assignment1/main.cpp -o main
问题是gcc正确编译main.cpp作为c ++代码（根据文件扩展名确定），但默认情况下不会链接libstdc++.a。因此未定义的参考错误。