我尝试运行代码时在Visual Studio中出现此错误：
1>c:\users\pprasha1\documents\visual studio 2008\projects\simulated-anneal\simulated-anneal\erstream.hpp(120) : error C2512: 'std::basic_ostream<_Elem,_Traits>' : no appropriate default constructor available
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
就这一行：
my_os(user_os),prog(NULL),errstatus(0) { } //HERE
以下是上下文的其余代码（搜索“HERE”以查找行）
#ifndef ERSTREAM_HPP_
#define ERSTREAM_HPP_ 1.6
#include <iostream>
#include <stdlib.h>
using namespace std;
#ifndef __GNUC__
#ifndef INHERIT_ERRORBUF
#define INHERIT_ERRORBUF
#endif
#endif
#ifndef INHERIT_ERRORBUF
class ErrorStream;
#endif
// the streambuf for the error handler, not used directly
class Errorbuf : public streambuf
{
private:
#ifndef INHERIT_ERRORBUF
ErrorStream *ehp; // NOT owned by the Errorbuf !!!
#endif
char *space;
protected:
virtual int doallocate();
public:
#ifdef INHERIT_ERRORBUF
Errorbuf() : space(NULL) {}
#else
Errorbuf() : ehp(NULL), space(NULL) {}
Errorbuf(ErrorStream* ehpl) : ehp(ehpl), space(NULL) {}
#endif
~Errorbuf();
#ifndef INHERIT_ERRORBUF
void associate(ErrorStream* ehpl) { ehp = ehpl; }
virtual int overflow(int c = EOF);
#endif
#ifdef __GNUC__
virtual int underflow() { return EOF; }
#endif
virtual int sync();
};
class ErrorStream;
struct ErrManipRec // struct for single parameter manipulator
{
int arg;
void (*fp)(ErrorStream& ehr, const int a);
ErrManipRec( void (*f)(ErrorStream& f, const int a ), const int a)
: fp(f), arg(a) {}
};
// The actual error handler class
#ifdef INHERIT_ERRORBUF
class ErrorStream : public Errorbuf, public ostream, virtual public ios
#else
class ErrorStream : public ostream, virtual public ios
#endif
{
#ifndef INHERIT_ERRORBUF
friend Errorbuf;
#endif
private:
static long int efirst;
static long int elast;
static long int msgnum; // count of warning messages
int errstatus;
int errcount;
ostream& my_os;
char *prog;
void nomore();
friend void Warning(ErrorStream& ehr, const int eval);
friend void Fail(ErrorStream& ehr, const int eval);
friend void Fatal(ErrorStream& ehr, const int eval);
protected:
virtual int write_buf(const char* s, const int len, const int eof);
#ifndef INHERIT_ERRORBUF
Errorbuf buffr;
#endif
ErrorStream(const ErrorStream& er);
public:
ErrorStream(ostream& user_os = cerr) : errcount(0),
#ifdef INHERIT_ERRORBUF
ios( (streambuf*)this ),
#else
ios(&buffr),buffr((ErrorStream*)this),
#endif
my_os(user_os),prog(NULL),errstatus(0) { } //HERE
ErrorStream(const char *s,ostream& user_os = cerr);
~ErrorStream();
#ifdef INHERIT_ERRORBUF
virtual int overflow(int c = EOF);
#else
virtual int sync() { return buffr.sync(); }
#endif
void close();
void reset() { errstatus = 0; }
int status() const { return errstatus; }
int count() const { return errcount; }
static void first_message(const long int fmsg) { efirst = fmsg-1; }
static void maximum_messages(const long int mxmsg) { elast = mxmsg+1; }
// set the error status
ErrorStream& operator=(const int err);
// add to the error status
ErrorStream& operator|=(const int err);
// increment the error status (pre-increment)
ErrorStream& operator++()
{ errstatus++; return *this; }
#ifndef __ATT2__
// increment the error status (post-increment)
#ifndef __GNUC__
ErrorStream operator++(int); // DOES NOT WORK WITH GCC
#endif
#endif
ErrorStream& operator+=(const int inc)
{ errstatus += inc; return *this; }
// one way to write error messages
void warning(const char *msg = NULL);
void nonfatal(const char *msg = NULL) { warning(msg); }
void fatal(const char * = NULL );
void fail(const char *msg = NULL);
void memory(const void * = NULL );
void warning(const int eval, const char *msg = NULL);
void nonfatal(const int eval, const char *msg = NULL)
{ warning(eval, msg); }
void fatal(const int eval, const char *msg = NULL);
void fail(const int eval, const char *msg = NULL);
void memory(const int eval, const void * = NULL );
// maninpulator version of fatal and warning
friend ErrorStream& fatal(ErrorStream& er)
{ er.fatal(); return er; }
friend ErrorStream& warning(ErrorStream& er)
{ er.warning(); return er; }
friend ErrorStream& fail(ErrorStream& er)
{ er.fail(); return er; }
friend ErrManipRec fatal(const int eval)
{ return ErrManipRec(::Fatal,eval); }
friend ErrManipRec warning(const int eval)
{ return ErrManipRec(::Warning,eval); }
friend ErrManipRec fail(const int eval)
{ return ErrManipRec(::Fail,eval); }
typedef ErrorStream& (*ErrManip)(ErrorStream&);
// applicator for the zero parameter manipulators
friend ErrorStream& operator<<(ErrorStream& err, ErrManip f)
{ (*f)( err ); return err; }
// applicator for the one parameter manipulators
friend ErrorStream& operator<<(ErrorStream& err, ErrManipRec r)
{ r.fp(err, r.arg ); return err; }
};
// a nonmember functions, mostly so I remember how to do a manipulator
ostream& terminate(ostream& os);
#endif
答案 0 :(得分：4)
class ErrorStream : public ostream, virtual public ios
{
表示您的ErrorStream是ostream的一种，这意味着它本身的一部分是ostream。
ostream& my_os;
这表示您的ErrorStream 也包含对ostream对象的引用。我很确定这两个中的一个是错的。 ErrorStream是一个流，还是包含对流的引用？由于您似乎默认为cerr，我相信您想要该会员。
ErrorStream(ostream& user_os = cerr) : errcount(0),
ios(&buffr),buffr((ErrorStream*)this),
my_os(user_os),prog(NULL),errstatus(0) { } //HERE
此构造函数导致错误，因为您初始化成员my_os，但您从未告诉它如何构造父ostream对象。编译器有助于尝试默认构造它，但ostream不能默认构造。因此，编译器不知道如何构造父ostream和错误。
修复程序会很复杂，但第一步是删除ostream父级。如果要保留某些功能，可以添加转换运算符
operator std::ostream&() {return my_os;}
在某些情况下，您可以假装ErrorStream是ostream。