Hi!
As the testcase shows, calling cp_build_bit_cast in tsubst_copy doesn't seem
to be a good idea, because tsubst_copy might not really make the operand
non-dependent, but as processing_template_decl can be 0,
type_dependent_expression_p will return false and then cp_build_bit_cast
assumes the type is non-NULL and non-dependent.
So, this patch just follows what is done e.g. for NOP_EXPR etc. and just
builds some tree in tsubst_copy, and only calls the semantics.c function
from tsubst_copy_and_build.
Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
2021-01-07 Jakub Jelinek <ja...@redhat.com>
PR c++/98329
* pt.c (tsubst_copy) <case BIT_CAST_EXPR>: Don't call
cp_build_bit_cast here, instead just build_min a BIT_CAST_EXPR and set
its location.
(tsubst_copy_and_build): Handle BIT_CAST_EXPR.
* g++.dg/cpp2a/bit-cast10.C: New test.
--- gcc/cp/pt.c.jj 2021-01-05 22:33:41.635816799 +0100
+++ gcc/cp/pt.c 2021-01-07 11:45:40.935610649 +0100
@@ -16796,7 +16796,9 @@ tsubst_copy (tree t, tree args, tsubst_f
{
tree type = tsubst (TREE_TYPE (t), args, complain, in_decl);
tree op0 = tsubst_copy (TREE_OPERAND (t, 0), args, complain, in_decl);
- return cp_build_bit_cast (EXPR_LOCATION (t), type, op0, complain);
+ r = build_min (BIT_CAST_EXPR, type, op0);
+ SET_EXPR_LOCATION (r, EXPR_LOCATION (t));
+ return r;
}
case SIZEOF_EXPR:
@@ -19631,6 +19633,13 @@ tsubst_copy_and_build (tree t,
RETURN (r);
}
+ case BIT_CAST_EXPR:
+ {
+ tree type = tsubst (TREE_TYPE (t), args, complain, in_decl);
+ tree op0 = RECUR (TREE_OPERAND (t, 0));
+ RETURN (cp_build_bit_cast (EXPR_LOCATION (t), type, op0, complain));
+ }
+
case POSTDECREMENT_EXPR:
case POSTINCREMENT_EXPR:
op1 = tsubst_non_call_postfix_expression (TREE_OPERAND (t, 0),
--- gcc/testsuite/g++.dg/cpp2a/bit-cast10.C.jj 2021-01-07 11:48:02.998020930
+0100
+++ gcc/testsuite/g++.dg/cpp2a/bit-cast10.C 2021-01-07 11:47:52.224141482
+0100
@@ -0,0 +1,42 @@
+// PR c++/98329
+// { dg-do compile { target c++20 } }
+
+template <typename To, typename From>
+constexpr To
+foo (const From &from)
+{
+ return __builtin_bit_cast (To, &from);
+}
+
+template <typename To, typename From>
+constexpr To
+bar (const From &from)
+{
+ return __builtin_bit_cast (To, *from);
+}
+
+template <typename To, typename From>
+constexpr To
+baz (const From &from)
+{
+ return __builtin_bit_cast (To, **from);
+}
+
+template <typename To, typename From>
+constexpr To
+qux (const From &from)
+{
+ return __builtin_bit_cast (To, -from);
+}
+
+void
+test ()
+{
+ int i = 0;
+ int *j = &i;
+ int **k = &j;
+ foo <char *> (i);
+ bar <int> (j);
+ baz <int> (k);
+ qux <int> (i);
+}
Jakub
