Boost C++ Libraries: Ticket #8327: iostream header and std::cout in hpp files must be removed.

John Maddock — Sat, 23 Mar 2013 11:29:39 GMT

There are several points here:

1) The compiler is entitled to reject PrintTest if std::endl and std::distance have not been declared even if the function is never instantiated. GCC and Clang are examples that will do this.

2) iostream and associated headers are part of the standard, it's not unreasonable to reply on them.

3) The only Math lib header mentioned above is only ever used when generating new numeric constants so should never be an issue in practice.

There is an include of <iostream> in boost/math/tools/precision.hpp which isn't needed which I'll remove.

And finally, please file one bug report per library.

pjtsu — Sat, 23 Mar 2013 13:43:05 GMT

Replying to johnmaddock:

Thank you for your reply.

1) The compiler is entitled to reject PrintTest if std::endl and std::distance have not been declared even if the function is never instantiated. GCC and Clang are examples that will do this.

Sorry, I did not check on GCC.

2) iostream and associated headers are part of the standard, it's not unreasonable to reply on them.

Windows GUI application can build with cout, but the application don't have I/O console.
Therefore ostringstream, ofstream or user-customized stream like may be used alternativelly.
If stream argument is not ostream but template-type, independent class from ostream can be used. (as like CDumpContext in MFC. ... though std::endl must be removed.)

// not so great
template <typename Iter>
void PrintTest(std::ostream& ostr, Iter first, Iter last);
// good
template <typename Stream, typename Iter>
void PrintTest(Stream& ostr, Iter first, Iter last);

3) The only Math lib header mentioned above is only ever used when generating new numeric constants so should never be an issue in practice.

There is an include of <iostream> in boost/math/tools/precision.hpp which isn't needed which I'll remove.

And finally, please file one bug report per library.

All right.

pjtsu — Sat, 23 Mar 2013 15:04:24 GMT

Incidentally, override of std::endl and std::flush for CDumpContext in MFC is as below. (I checked only vs2010.)

inline CDumpContext& operator << (CDumpContext& me, CDumpContext & (*_f)(CDumpContext&)) { return (*_f)(me); }
namespace std {
        inline CDumpContext& flush(CDumpContext& me) { me.Flush(); return me; }
        inline CDumpContext& endl(CDumpContext& me) { return me << _T("\n") << flush; }
};

John Maddock — Sat, 23 Mar 2013 16:53:01 GMT

class Stream and CDumpContext are entirely specific to MSVC, they won't appear anywhere in Boost code.

Also note that std::iostream code is only used in Boost.Math for debugging/diagnostic purposes (when BOOST_MATH_INSTRUMENT is defined). What is used is boost::lexical_cast which depends on std::stringstream and related code. Removing that is much harder - verging on impossible if we want to retain multiprecision support - which we certainly do.

John Maddock — Sat, 23 Mar 2013 17:05:20 GMT

(In [83532]) Reorganise header inclusion to minimise dependencies on <iostream> and <boost/lexical_cast.hpp>. Refs #8327.

status changed; resolution set

John Maddock — Sun, 24 Mar 2013 12:02:01 GMT

status new → closed
resolution → fixed

(In [83537]) Make use of lexical_cast (and hence multiprecision support) dependent on there being an iostreams lib. Should allow use on embedded platforms, especially WinCE. Fixes #8327.