OPTCHARS

OPTCHARS is a list defining the characters the compiler/ linker command allows to specify an option (typically "-" or "/").

If some option characters can be used interchangeably on the command line, those characters are given without a separator. Otherwise, a comma is used for separation.

Examples:
OPTCHARS = -
OPTCHARS = -,+
OPTCHARS = -/
In the second example, some options start solely by "-" and some others solely by "+". In the third example, all options can start either with "-" or with "/" (as for example with Microsoft cl).