On Mon, Aug 25, 2025 at 09:44:29AM -0400, Jason Merrill wrote:
> > --- gcc/cp/pt.cc.jj 2025-08-23 15:00:04.262787988 +0200
> > +++ gcc/cp/pt.cc 2025-08-23 15:51:08.726081054 +0200
> > @@ -22321,6 +22321,13 @@ tsubst_expr (tree t, tree args, tsubst_f
> > if (DECL_NAME (t) == this_identifier && current_class_ptr)
> > RETURN (current_class_ptr);
> > + /* Parameters during expansion stmt body instantiation outside
> > + of templates map to themselves. */
> > + if (current_tinst_level
> > + && (TREE_CODE (current_tinst_level->tldcl)
> > + == TEMPLATE_FOR_STMT))
> > + RETURN (t);
>
> Rather than checking specifically for an expansion stmt, I'd prefer to check
> for the general case of the parameter not being in a template, perhaps with
>
> if (!uses_template_parms (DECL_CONTEXT (t))
>
> since that test is already used in the controlling if?
That works too on
GXX_TESTSUITE_STDS=98,11,14,17,20,23,26 make check-g++
RUNTESTFLAGS="dg.exp='expansion-stmt*'"
too, ok for trunk if it passes full bootstrap/regtest?
2025-08-25 Jakub Jelinek <ja...@redhat.com>
Jason Merrill <ja...@redhat.com>
PR c++/121575
* pt.cc (tsubst_expr) <case PARM_DECL>: If DECL_CONTEXT (t) isn't a
template return t for PARM_DECLs without local specialization.
* g++.dg/cpp26/expansion-stmt20.C: New test.
--- gcc/cp/pt.cc.jj 2025-08-25 16:29:07.122358976 +0200
+++ gcc/cp/pt.cc 2025-08-25 16:45:15.210314704 +0200
@@ -22321,6 +22321,11 @@ tsubst_expr (tree t, tree args, tsubst_f
if (DECL_NAME (t) == this_identifier && current_class_ptr)
RETURN (current_class_ptr);
+ /* Parameters of non-templates map to themselves (e.g. in
+ expansion statement body). */
+ if (!uses_template_parms (DECL_CONTEXT (t)))
+ RETURN (t);
+
/* This can happen for a parameter name used later in a function
declaration (such as in a late-specified return type). Just
make a dummy decl, since it's only used for its type. */
--- gcc/testsuite/g++.dg/cpp26/expansion-stmt20.C.jj 2025-08-25
16:43:07.510020392 +0200
+++ gcc/testsuite/g++.dg/cpp26/expansion-stmt20.C 2025-08-25
16:43:07.510020392 +0200
@@ -0,0 +1,59 @@
+// PR c++/121575
+// { dg-do run { target c++11 } }
+// { dg-options "" }
+
+struct A { int x, y; };
+int c;
+
+void
+qux (A p)
+{
+ if (p.x != 1 || p.y != 3)
+ __builtin_abort ();
+ ++c;
+}
+
+void
+foo ()
+{
+ A p { 1, 3 };
+ template for (auto _ : {}) // { dg-warning "'template for'
only available with" "" { target c++23_down } }
+ qux (p);
+ template for (auto _ : { 0 }) // { dg-warning
"'template for' only available with" "" { target c++23_down } }
+ qux (p);
+}
+
+void
+bar (A p)
+{
+ template for (auto _ : {}) // { dg-warning "'template for'
only available with" "" { target c++23_down } }
+ qux (p);
+ template for (auto _ : { 0, 1 }) // { dg-warning "'template for'
only available with" "" { target c++23_down } }
+ qux (p);
+}
+
+A
+baz ()
+{
+ A p { 1, 3 };
+ template for (auto _ : {}) // { dg-warning "'template for'
only available with" "" { target c++23_down } }
+ qux (p);
+ template for (auto _ : { 0, 1, 2 }) // { dg-warning "'template for'
only available with" "" { target c++23_down } }
+ qux (p);
+ return p;
+}
+
+int
+main ()
+{
+ foo ();
+ if (c != 1)
+ __builtin_abort ();
+ bar ({ 1, 3 });
+ if (c != 3)
+ __builtin_abort ();
+ if (baz ().x != 1 || baz ().y != 3)
+ __builtin_abort ();
+ if (c != 9)
+ __builtin_abort ();
+}
Jakub
