这里我有这个streambuf
,ostream
结构(从这里http://wordaligned.org/articles/cpp-streambufs修改),在这里我尝试从代码中的两点开始throw
。但是我永远无法在main()
中捕获这些异常,并且程序可以正常退出。这是什么原因?
#include <iostream>
#include <fstream>
#include <streambuf>
using namespace std;
class teebuf: public streambuf
{
public:
teebuf(streambuf * sb1, streambuf * sb2)
: sb1(sb1) ,
sb2(sb2)
{ }
private:
virtual int overflow(int c) {
if (c == EOF)
return !EOF;
else {
//Throwing here
throw exception();
int const r1 = sb1->sputc(c);
int const r2 = sb2->sputc(c);
return r1 == EOF || r2 == EOF ? EOF : c;
}
}
virtual int sync() {
//Throwing here
throw exception();
int const r1 = sb1->pubsync();
int const r2 = sb2->pubsync();
return r1 == 0 && r2 == 0 ? 0 : -1;
}
private:
streambuf * sb1;
streambuf * sb2;
};
class teestream : public ostream
{
public:
teestream(ostream & o1, ostream & o2);
private:
teebuf tbuf;
};
teestream::teestream(ostream & o1, ostream & o2)
: std::ostream(&tbuf) ,
tbuf(o1.rdbuf(), o2.rdbuf())
{ }
int main() {
ofstream log("hello-world.log");
teestream tee(cout, log);
try {
tee << "Hello, world!\n";
} catch(...) {
//Catching here
cerr << "Exception" << endl;
}
return 0;
}
最佳答案
默认情况下,将流设置为具有防毒面具,以捕获所有内容。如果要让异常在流中传播,则需要设置异常(exception)掩码以允许这样做。
具体来说,您需要设置std::ios_base::badbit
来重新抛出异常(在流上设置std::ios_base::badbit
之后):
stream.exceptions(std::ios_base::badbit);