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cp-class.h
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C/C++ Source or Header
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1994-02-06
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3KB
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94 lines
/* The following structure is used when comparing various alternatives
for overloading. The unsigned quantity `strikes.i' is used
for fast comparison of two possibilities. This number is an
aggregate of four constituents:
EVIL: if this is non-zero, then the candidate should not be considered
USER: if this is non-zero, then a user-defined type conversion is needed
B_OR_D: if this is non-zero, then use a base pointer instead of the
type of the pointer we started with.
EASY: if this is non-zero, then we have a builtin conversion
(such as int to long, int to float, etc) to do.
If two candidates require user-defined type conversions, and the
type conversions are not identical, then an ambiguity error
is reported.
If two candidates agree on user-defined type conversions,
and one uses pointers of strictly higher type (derived where
another uses base), then that alternative is silently chosen.
If two candidates have a non-monotonic derived/base pointer
relationship, and/or a non-monotonic easy conversion relationship,
then a warning is emitted to show which paths are possible, and
which one is being chosen.
For example:
int i;
double x;
overload f;
int f (int, int);
double f (double, double);
f (i, x); // draws a warning
struct B
{
f (int);
} *bb;
struct D : B
{
f (double);
} *dd;
dd->f (x); // exact match
dd->f (i); // draws warning
Note that this technique really only works for 255 arguments. Perhaps
this is not enough. */
struct candidate
{
tree function; /* A FUNCTION_DECL */
unsigned char evil; /* !0 if this will never convert. */
unsigned char user; /* !0 if at least one user-defined type conv. */
unsigned short b_or_d; /* count number of derived->base or
base->derived conv. */
unsigned short easy; /* count number of builtin type conv. */
tree arg; /* first parm to function. */
unsigned short *harshness; /* Indexed by argument number, encodes
evil, user, d_to_b, and easy strikes for
that argument.
At end of array, we store the index+1
of where we started using default
parameters, or 0 if there are none. */
union
{
tree field; /* If no evil strikes, the FUNCTION_DECL of
the function (if a member function). */
int bad_arg; /* the index of the first bad argument:
0 if no bad arguments
> 0 is first bad argument
-1 if extra actual arguments
-2 if too few actual arguments.
-3 if const/non const method mismatch.
-4 if type unification failed.
-5 if contravariance violation. */
} u;
};
int rank_for_overload ();
/* Variables shared between cp-class.c and cp-call.c. */
extern int n_vtables;
extern int n_vtable_entries;
extern int n_vtable_searches;
extern int n_vtable_elems;
extern int n_convert_harshness;
extern int n_compute_conversion_costs;
extern int n_build_method_call;
extern int n_inner_fields_searched;