DECL_INTERFACE_KNOWN (result) = 1;
}
+/* Subroutine of more_specialized_fn: check whether TARGS is missing any
+ important template arguments. If any are missing, we check whether
+ they're important by using error_mark_node for substituting into any
+ args that were used for partial ordering (the ones between ARGS and END)
+ and seeing if it bubbles up. */
+
+static bool
+check_undeduced_parms (tree targs, tree args, tree end)
+{
+ bool found = false;
+ int i;
+ for (i = TREE_VEC_LENGTH (targs) - 1; i >= 0; --i)
+ if (TREE_VEC_ELT (targs, i) == NULL_TREE)
+ {
+ found = true;
+ TREE_VEC_ELT (targs, i) = error_mark_node;
+ }
+ if (found)
+ {
+ for (; args != end; args = TREE_CHAIN (args))
+ {
+ tree substed = tsubst (TREE_VALUE (args), targs, tf_none, NULL_TREE);
+ if (substed == error_mark_node)
+ return true;
+ }
+ }
+ return false;
+}
+
/* Given two function templates PAT1 and PAT2, return:
1 if PAT1 is more specialized than PAT2 as described in [temp.func.order].
neither is more cv-qualified, they both are equal). Unlike regular
deduction, after all the arguments have been deduced in this way,
we do *not* verify the deduced template argument values can be
- substituted into non-deduced contexts, nor do we have to verify
- that all template arguments have been deduced. */
+ substituted into non-deduced contexts.
+
+ The logic can be a bit confusing here, because we look at deduce1 and
+ targs1 to see if pat2 is at least as specialized, and vice versa; if we
+ can find template arguments for pat1 to make arg1 look like arg2, that
+ means that arg2 is at least as specialized as arg1. */
int
more_specialized_fn (tree pat1, tree pat2, int len)
tree tparms2 = DECL_INNERMOST_TEMPLATE_PARMS (pat2);
tree args1 = TYPE_ARG_TYPES (TREE_TYPE (decl1));
tree args2 = TYPE_ARG_TYPES (TREE_TYPE (decl2));
- int better1 = 0;
- int better2 = 0;
+ tree origs1, origs2;
+ bool lose1 = false;
+ bool lose2 = false;
/* Remove the this parameter from non-static member functions. If
one is a non-static member function and the other is not a static
processing_template_decl++;
+ origs1 = args1;
+ origs2 = args2;
+
while (len--
/* Stop when an ellipsis is seen. */
&& args1 != NULL_TREE && args2 != NULL_TREE)
deduce2 = !unify (tparms2, targs2, arg2, arg1, UNIFY_ALLOW_NONE);
}
+ /* If we couldn't deduce arguments for tparms1 to make arg1 match
+ arg2, then arg2 is not as specialized as arg1. */
if (!deduce1)
- better2 = -1;
+ lose2 = true;
if (!deduce2)
- better1 = -1;
- if (better1 < 0 && better2 < 0)
- /* We've failed to deduce something in either direction.
- These must be unordered. */
- break;
-
- if (deduce1 && deduce2 && quals1 >= 0 && quals2 >= 0)
+ lose1 = true;
+
+ /* "If, for a given type, deduction succeeds in both directions
+ (i.e., the types are identical after the transformations above)
+ and if the type from the argument template is more cv-qualified
+ than the type from the parameter template (as described above)
+ that type is considered to be more specialized than the other. If
+ neither type is more cv-qualified than the other then neither type
+ is more specialized than the other."
+
+ We check same_type_p explicitly because deduction can also succeed
+ in both directions when there is a nondeduced context. */
+ if (deduce1 && deduce2
+ && quals1 != quals2 && quals1 >= 0 && quals2 >= 0
+ && same_type_p (arg1, arg2))
{
- /* Deduces in both directions, see if quals can
- disambiguate. Pretend the worse one failed to deduce. */
if ((quals1 & quals2) == quals2)
- deduce1 = 0;
+ lose2 = true;
if ((quals1 & quals2) == quals1)
- deduce2 = 0;
+ lose1 = true;
}
- if (deduce1 && !deduce2 && !better2)
- better2 = 1;
- if (deduce2 && !deduce1 && !better1)
- better1 = 1;
+
+ if (lose1 && lose2)
+ /* We've failed to deduce something in either direction.
+ These must be unordered. */
+ break;
if (TREE_CODE (arg1) == TYPE_PACK_EXPANSION
|| TREE_CODE (arg2) == TYPE_PACK_EXPANSION)
args2 = TREE_CHAIN (args2);
}
+ /* "In most cases, all template parameters must have values in order for
+ deduction to succeed, but for partial ordering purposes a template
+ parameter may remain without a value provided it is not used in the
+ types being used for partial ordering."
+
+ Thus, if we are missing any of the targs1 we need to substitute into
+ origs1, then pat2 is not as specialized as pat1. This can happen when
+ there is a nondeduced context. */
+ if (!lose2 && check_undeduced_parms (targs1, origs1, args1))
+ lose2 = true;
+ if (!lose1 && check_undeduced_parms (targs2, origs2, args2))
+ lose1 = true;
+
processing_template_decl--;
/* All things being equal, if the next argument is a pack expansion
for one function but not for the other, prefer the
- non-variadic function. */
- if ((better1 > 0) - (better2 > 0) == 0
+ non-variadic function. FIXME this is bogus; see c++/41958. */
+ if (lose1 == lose2
&& args1 && TREE_VALUE (args1)
&& args2 && TREE_VALUE (args2))
{
- if (TREE_CODE (TREE_VALUE (args1)) == TYPE_PACK_EXPANSION)
- return TREE_CODE (TREE_VALUE (args2)) == TYPE_PACK_EXPANSION ? 0 : -1;
- else if (TREE_CODE (TREE_VALUE (args2)) == TYPE_PACK_EXPANSION)
- return 1;
+ lose1 = TREE_CODE (TREE_VALUE (args1)) == TYPE_PACK_EXPANSION;
+ lose2 = TREE_CODE (TREE_VALUE (args2)) == TYPE_PACK_EXPANSION;
}
- return (better1 > 0) - (better2 > 0);
+ if (lose1 == lose2)
+ return 0;
+ else if (!lose1)
+ return 1;
+ else
+ return -1;
}
/* Determine which of two partial specializations is more specialized.
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