为什么写入空std:：istringstream.rdbuf（）会设置失败位？ 我已经学会了，我可以通过输出ISTRAMS的RDBUFF（）来复制C++ STD::ISTrAM到C++ STD:：OFROW。我用了好几次，效果很好

今天我遇到了麻烦，因为如果std:：istream为空（至少对于std:：istringstream），该操作会设置badbit。我已经编写了以下代码来演示我的问题：

#include <stdio.h>
#include <sstream>

int main(int argc, char *argv[])
{
    std::ostringstream ss;

    ss << std::istringstream(" ").rdbuf(); // this does not set failbit
    printf("fail=%d\n", ss.fail());

    ss << std::istringstream("").rdbuf(); // why does this set failbit ???
    printf("fail=%d\n", ss.fail());
}

#包括
#包括
int main（int argc，char*argv[]）
{
std：：ostringstream ss；
ssostream:：operator的文档
#include <stdio.h>
#include <sstream>

int main(int argc, char *argv[])
{
    std::ostringstream out;
    std::istringstream in("");
    while (in)
    {
        char Buffer[4096];
        in.read(Buffer, sizeof(Buffer));
        out.write(Buffer, in.gcount());
    }
    printf("fail=%d\n", out.fail());
}

   * end-of-file occurs on the input sequence;
   * inserting in the output sequence fails (in which case the character to be inserted is not extracted);
   * an exception occurs (in which case the exception is caught).