Beman Dawes wrote:
The C++ committee accepted what is essentially Boost.System for C++0x. See http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2007/n2241.html for the final proposal.
Looks nice. With one issue: This document has following wording: virtual string message(error_code::value_type ev) const=0; Returns: A string that describes the error condition denoted by ev. [Note: The intent is to return a locale sensitive string that describes the error corresponding to ev. --end note.] Throws: Nothing. virtual wstring wmessage(error_code::value_type ev) const=0; Returns: A string that describes the error condition denoted by ev. [Note: The intent is to return a locale sensitive string that describes the error corresponding to ev. --end note.] Throws: Nothing. [snip] class error_code { public: // snipped code string message() const; wstring wmessage() const; // snipped code }; locale sensitivity is good, but in this form user is enforced to set/unset global locale each time he wants to use locale sensitive output from error_category like this: std::locale oldLocale = std::locale::global(myLocale); std::cout << err_cat.message(ev); std::locale::global(oldLocale); It is tedious, requires additional work to make it exception safe and thread safe. I propose to change wording to the following: virtual string message(error_code::value_type ev, std::locale loc = std::locale()) const=0; Returns: A string that describes the error condition denoted by ev. [Note: The intent is to return a locale sensitive string that describes the error corresponding to ev. --end note.] Throws: Nothing. virtual wstring wmessage(error_code::value_type ev, std::locale loc = std::locale()) const=0; Returns: A string that describes the error condition denoted by ev. [Note: The intent is to return a locale sensitive string that describes the error corresponding to ev. --end note.] Throws: Nothing. [snip] class error_code { public: // snipped code string message(std::locale loc = std::locale()) const; wstring wmessage(std::locale loc = std::locale()) const; // snipped code }; Then user code would be as simple as: std::cout << err_cat.message(ev, myLocale); global state is not touched here, so no problems with exception and thread safety (I don't take cout into account here) Oleg Abrosimov.