Availability:C-language interface function
bool PL_set_prolog_flag(const 
char *name, int type, ...)Set/create a Prolog flag from C. name is the name of the 
affected flag. type is one of the values below, which also 
dictates the type of the final argument. The function returns
TRUE on success and FALSE on failure. This 
function can be called before PL_initialise(), 
making the flag available to the Prolog startup code.
- PL_BOOL
- Create a boolean (trueorfalse) flag. The 
argument must be anint.
- PL_ATOM
- Create a flag with an atom as value. The argument must be of type
const char *.
- PL_INTEGER
- Create a flag with an integer as value. The argument must be of type
intptr_t *.