Peter Dimov wrote:
I think that we also need to consider the problem of translating a
filesystem_error to a localized error message.
In particular, consider this example of a what() string:
File system error: move_file(): nonexistent, something_else: The system
cannot find the file specified.
generated by
boost::filesystem::rename("nonexistent", "something_else");
There is no way to localize it, as it (a) contains non-localizable dynamic
path names embedded within the message,
Seems like there is quite a few alternatives:
1. Perform localization at the point where exception is thrown. The biggest
problem there is getting the right message catalog.
- I don't like standard message catalogs at all, because they require
integer ids. And are they implemented anywhere, btw? It's possible
to add gettext-like message catalog facet to locale, though.
- What locale to use? Global? -- not sure. Locale passed to the
function that throws --- uhmm... passing locale to every filesystem
function is plain boring.
2. Keep the format string and variable arguments in exception class.
This is similiar, but IMO, different from the idea to specify values
of 'what'. E.g
class filesystem_exception {
public:
const string& format_string() const;
const vector<string>& parameters() const;
const char* what() const {
boost::format f(format_string());
const vector<string>& p = parameters();
for (size_t i = 0; i < p.size(); ++i)
f % p[i];
// Do something tricky to return pointer
// to f.str().c_str(), but prevent the
// string from going out of scope.
}
void imbue(const locale&);
};
So, if you want to get localized "what", you'll imbue the appropriate
locale. How does that look?
Don't really know how to localize parameters themself...
and (b) the "The system..." part
obtained from FormatMessage may already have been localized by the OS.
I think that you should know if it's localized or not somehow, and make it
localized if possible. Otherwise, we're back to the problem of localizing
arguments.
- Volodya
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