MPFR, printf, decimal places, locales, file i/o problem

A user of my program has reported problems reading a settings file written by my program. I looked at the settings file in question and instead of decimal points using the period "." it uses commas ",".

I'm assuming this is to do with locales?

The file i/o is using fprintf and mpfr_out_str for file output and getline combined with atol, atof, mpfr_set_str, etc for file input.

What do I do here? Should I force my program to always use periods even if the machine's locale wants to use commas? If so, where do I start?

Edit: I've just noticed that this problem occurs when specifying the settings file to use on the comman开发者_如何转开发d line instead of loading it via the GUI - would this indicate a problem on the OP's machine or in my code?

Do you call setlocale at all? If not, I would suggest either embedding the locale used to generate the file in the settings file or force all settings file I/O to use the C locale, via the previous suggestion of setlocale(LC_ALL, "C").

One other option is to use the locale specific formatting functions (suffixed with _l in MSVC) and create the C locale explicitly, via _create_locale(LC_ALL, "C").