12.4.26 Locale and PL_initialise()

PL_initialise() reads the numeric conventions (decimal point, thousands separator, digit grouping) of the environment's LC_NUMERIC locale for use by locale-sensitive predicates such as format/3 with  :d and  :f directives. See section 4.23. It does so without calling setlocale(), so the embedder's process locale is left untouched and functions such as atof() and printf()("%f") continue to use the decimal point that was in effect before PL_initialise() was called.

PL_initialise() does call setlocale() for LC_CTYPE (to pick up the multibyte encoding used for atoms and streams), LC_TIME and LC_COLLATE. Embedders that require a strict "C" locale for these categories should either arrange the environment before starting the process or reset the desired categories after PL_initialise() returns.