我正在将一些代码移植到Darwin OS X,这意味着我们需要从gcc编译器转换为clang编译器。
代码中有一个函数,始于2005年并在互联网上发布了几个版本。它提供了多个不同版本的GCC的功能,我已经删掉了除最后一个v3.4.0或更高版本之外的所有内容。该代码依赖于两个GCC特定的类:
代码中有一个函数,始于2005年并在互联网上发布了几个版本。它提供了多个不同版本的GCC的功能,我已经删掉了除最后一个v3.4.0或更高版本之外的所有内容。该代码依赖于两个GCC特定的类:
__gnu_cxx::stdio_filebuf
和 __gnu_cxx::stdio_sync_filebuf
。//! Similar to fileno(3), but taking a C++ stream as argument instead of a
//! FILE*. Note that there is no way for the library to track what you do with
//! the descriptor, so be careful.
//! \return The integer file descriptor associated with the stream, or -1 if
//! that stream is invalid. In the latter case, for the sake of keeping the
//! code as similar to fileno(3), errno is set to EBADF.
//! \see The <A HREF="http://www.ginac.de/~kreckel/fileno/">upstream page at
//! http://www.ginac.de/~kreckel/fileno/</A> of this code provides more
//! detailed information.
template <typename charT, typename traits>
inline int
fileno_hack(const std::basic_ios<charT, traits>& stream)
{
// Some C++ runtime libraries shipped with ancient GCC, Sun Pro,
// Sun WS/Forte 5/6, Compaq C++ supported non-standard file descriptor
// access basic_filebuf<>::fd(). Alas, starting from GCC 3.1, the GNU C++
// runtime removes all non-standard std::filebuf methods and provides an
// extension template class __gnu_cxx::stdio_filebuf on all systems where
// that appears to make sense (i.e. at least all Unix systems). Starting
// from GCC 3.4, there is an __gnu_cxx::stdio_sync_filebuf, in addition.
// Sorry, darling, I must get brutal to fetch the darn file descriptor!
// Please complain to your compiler/libstdc++ vendor...
#if defined(__GLIBCXX__) || defined(__GLIBCPP__)
// OK, stop reading here, because it's getting obscene. Cross fingers!
# if defined(__GLIBCXX__) // >= GCC 3.4.0
// This applies to cin, cout and cerr when not synced with stdio:
typedef __gnu_cxx::stdio_filebuf<charT, traits> unix_filebuf_t;
unix_filebuf_t* fbuf = dynamic_cast<unix_filebuf_t*>(stream.rdbuf());
if (fbuf != NULL) {
return fbuf->fd();
}
// This applies to filestreams:
typedef std::basic_filebuf<charT, traits> filebuf_t;
filebuf_t* bbuf = dynamic_cast<filebuf_t*>(stream.rdbuf());
if (bbuf != NULL) {
// This subclass is only there for accessing the FILE*. Ouuwww, sucks!
struct my_filebuf : public std::basic_filebuf<charT, traits> {
int fd() { return this->_M_file.fd(); }
};
return static_cast<my_filebuf*>(bbuf)->fd();
}
// This applies to cin, cout and cerr when synced with stdio:
typedef __gnu_cxx::stdio_sync_filebuf<charT, traits> sync_filebuf_t;
sync_filebuf_t* sbuf = dynamic_cast<sync_filebuf_t*>(stream.rdbuf());
if (sbuf != NULL) {
return fileno(sbuf->file());
}
# endif
#else
# error "Does anybody know how to fetch the bloody file descriptor?"
return stream.rdbuf()->fd(); // Maybe a good start?
#endif
errno = EBADF;
return -1;
}
问题是,在 OS X Mavericks 上的 clang 5.1 中,如何计算 std::basic_ios
的文件描述符呢?
basic_filebuf
类似乎将一个stdioFILE
包装起来,而不是直接使用操作系统级别的文件描述符。但是我没有找到任何从filebuf
中提取FILE
或从已经打开的FILE
创建filebuf
的方法。也许有比我更聪明的人知道怎么做。 - zwolreturn -1
和errno == EBADF
的情况。 - WilliamKF