我有以下代码，到目前为止，我想检查文件名是否已经在链接列表fileList（或flist）中。根据输出，保存在第一个节点中的字符串在Node* getFileName(Node *&flist)的某处发生了变化。这是怎么发生的？另外，对于Node和字符串的指针，还有其他任何我做错了或不安全吗？
输出：
in main: file4.txt start of process: file4.txt file4.txt mid of process: file4.txt" in contains, fileName in node: file4.txt" in contains, target file name: file4.txt end of process: file4.txt" 0 no recursive call
代码：
struct Node {
string fileName;
Node *link;
};
/*
*
*/
bool contains (Node *&flist, string &name) {
Node *tempNode = *&flist;
while (tempNode != 0) {
cout << "in contains, fileName in node: " << flist->fileName << endl;
cout << "in contains, target file name: " << name << endl;
if ((tempNode->fileName) == name) {
return true;
}
else {
tempNode = tempNode->link;
}
}
return false;
}
/*
*
*/
Node* getLastNode (Node *&flist) {
Node *tempNode = *&flist;
while (tempNode != 0) {
tempNode = tempNode->link;
}
return tempNode;
}
/*
*
*/
string getFileName(string oneLine) {
char doubleQuote;
doubleQuote = oneLine[9];
if (doubleQuote == '\"') {
string sub = oneLine.substr(10); //getting the file name
string::size_type n = sub.size();
sub = sub.substr(0,n-1);
cout << sub << endl;
return sub;
}
return NULL;
}
/*
*
*/
void process( istream &in, ostream &out, Node *&flist ) {
cout << "start of process: " << flist->fileName << endl;
string oneLine; //temp line holder
while (getline(in, oneLine)) {
// cout << oneLine << endl;
string::size_type loc = oneLine.find("#include",0);
if (loc != string::npos) {
//found one line starting with "#include"
string name;
name = getFileName(oneLine);
cout << "mid of process: " << flist->fileName << endl;
bool recursive;
recursive = contains(flist, name);
cout << "end of process: " << flist->fileName << endl;
cout << recursive << endl;
if (recursive) {
//contains recursive include
cerr << "recursive include of file " << name << endl;
exit(-1);
}
else {
//valid include
cout << "no recursive call" << endl;
}//else
}//if
}//while
}//process
/*
*
*/
int main( int argc, char *argv[] ) {
istream *infile = &cin; // default value
ostream *outfile = &cout; // default value
Node* fileList;
switch ( argc ) {
case 3:
outfile = new ofstream( argv[2] ); // open the outfile file
if ( outfile->fail() ) {
cerr << "Can't open output file " << argv[2] << endl;
exit( -1 );
}
// FALL THROUGH to handle input file
case 2:
infile = new ifstream( argv[1] ); // open the input file
if ( infile->fail() ) {
cerr << "Can't open input file " << argv[1] << endl;
exit( -1 );
}
else {
Node aFile = {argv[1], 0};
fileList = &aFile;
cout << "in main: " << fileList->fileName << endl;
}
// FALL THROUGH
case 1: // use cin and cout
break;
default: // too many arguments
cerr << "Usage: " << argv[0] << " [ input-file [ output-file ] ]" << endl;
exit( -1 ); // TERMINATE!
}
processOneFile (*infile, *outfile, fileList);
// do something
if ( infile != &cin ) delete infile; // close file, do not delete cin!
if ( outfile != &cout ) delete outfile; // close file, do not delete cout!
}
答案 0 :(得分：2)
你能发布原始代码吗？您发布的代码甚至无法编译。
我注意到的错误，按顺序：
processOneFile (*infile, *outfile, fileList);
没有processOneFile()程序。
istream *infile = &cin; // default value
ostream *outfile = &cout; // default value
Node* fileList;
case 1: // use cin and cout
break;
processOneFile (*infile, *outfile, fileList);
这将使用未初始化的文件列表调用processOneFile()，当您尝试打印文件名时，该列表将崩溃。
else {
Node aFile = {argv[1], 0};
fileList = &aFile;
cout << "in main: " << fileList->fileName << endl;
}
aFile仅在else范围内，因此稍后尝试使用指针会失败。
string getFileName(string oneLine) {
///
return NULL;
}
您无法从std::string构建NULL - 这会导致程序崩溃。
修复这些错误后，您的代码不会崩溃，我无法重现错误。
如果您在Linux中构建，请尝试提高警告级别（使用g++ -Wall -Wextra -ansi -pedantic）并通过valgrind运行代码，以检查内存错误。
答案 1 :(得分：0)
好的，代码现在看起来像预期的那样工作：
#include <iostream>
#include <fstream>
using namespace::std;
struct Node
{
string fileName;
Node *link;
};
bool contains (Node *&flist, string &name)
{
Node *tempNode = *&flist;
while (tempNode != 0)
{
cout << "Searching in \"" << flist->fileName;
cout << "\" for \"" << name << "\"" << endl;
if ( tempNode->fileName == name)
{
return true;
}
else
{
tempNode = tempNode->link;
}
}
return false;
}
Node* getLastNode (Node *&flist)
{
Node *tempNode = *&flist;
while (tempNode != 0)
{
tempNode = tempNode->link;
}
return tempNode;
}
string getFileName(string oneLine)
{
char doubleQuote;
doubleQuote = oneLine[9];
if (doubleQuote == '\"') {
string sub = oneLine.substr(10); //getting the file name
string::size_type n = sub.size();
sub = sub.substr(0,n-1);
return sub;
}
return "";
}
void process( istream &in, ostream &out, Node *&flist )
{
cout << "Start of process: " << flist->fileName << endl << endl;
string oneLine;
while (1)
{
cout << "Input include statement: ";
getline(in, oneLine);
if (oneLine == "STOP")
return;
string::size_type loc = oneLine.find("#include",0);
if (loc != string::npos)
{
//found one line starting with "#include"
string name;
name = getFileName(oneLine);
if (name == "")
{
cout << "Couldn't find filename, skipping line..." << endl;
continue;
}
if (contains(flist, name))
{
//contains recursive include
cerr << "Uh, oh! Recursive include of file " << name << endl;
exit(-1);
}
else
{
cerr << "No recursive include" << endl;
}
}//if
cout << endl;
}//while
}
int main( int argc, char *argv[] )
{
Node* fileList = new Node;
istream *infile = &cin; // default value
ostream *outfile = &cout; // default value
fileList->fileName = "Input"; // default value
switch ( argc )
{
case 3:
outfile = new ofstream( argv[2] ); // open the outfile file
if ( outfile->fail() ) {
cerr << "Can't open output file " << argv[2] << endl;
exit( -1 );
}
// FALL THROUGH to handle input file
case 2:
infile = new ifstream( argv[1] ); // open the input file
if ( infile->fail() ) {
cerr << "Can't open input file " << argv[1] << endl;
exit( -1 );
}
else {
fileList->fileName = argv[1];
cout << "in main: " << fileList->fileName << endl;
}
// FALL THROUGH
case 1: // use cin and cout
break;
default: // too many arguments
cerr << "Usage: " << argv[0] << " [ input-file [ output-file ] ]" << endl;
exit( -1 ); // TERMINATE!
}
process(*infile, *outfile, fileList);
// do something
if ( infile != &cin ) delete infile; // close file, do not delete cin!
if ( outfile != &cout ) delete outfile; // close file, do not delete cout!
}
答案 2 :(得分：0)
另外，当标准库已经有一个非常好的链接列表时，你为什么要浪费时间编写自己的链表呢？