On Wed, 10 Apr 2024, Jason Merrill wrote:
> On 3/12/24 10:51, Patrick Palka wrote:
> > On Tue, 12 Mar 2024, Patrick Palka wrote:
> > > On Tue, 12 Mar 2024, Jason Merrill wrote:
> > > > On 3/11/24 12:53, Patrick Palka wrote:
> > > > >
> > > > > r13-6452-g341e6cd8d603a3 made build_extra_args walk evaluated contexts
> > > > > first so that we prefer processing a local specialization in an
> > > > > evaluated
> > > > > context even if its first use is in an unevaluated context. But this
> > > > > means we need to avoid walking a tree that already has extra
> > > > > args/specs
> > > > > saved because the list of saved specs appears to be an evaluated
> > > > > context. It seems then that we should be calculating the saved specs
> > > > > from scratch each time, rather than potentially walking the saved
> > > > > specs
> > > > > list from an earlier partial instantiation when calling
> > > > > build_extra_args
> > > > > a second time around.
> > > >
> > > > Makes sense, but I wonder if we want to approach that by avoiding
> > > > walking into
> > > > *_EXTRA_ARGS in extract_locals_r? Or do we still want to walk into any
> > > > nested
> > > > extra args? And if so, will we run into this same problem then?
> > >
> > > I'm not sure totally but I'd expect a nested extra-args tree to always
> > > have empty *_EXTRA_ARGS since the outer extra-args tree should intercept
> > > any substitution before the inner extra-args tree can see it?
> >
> > ... and so in extract_locals_r I think we can assume *_EXTRA_ARGS is
> > empty, and not have to explicitly avoid walking it.
>
> It seems more robust to me to handle _EXTRA_ARGS appropriately in
> build_extra_args rather than expect callers to know that they shouldn't pass
> in a tree with _EXTRA_ARGS set. At least check and abort in that case?
Sounds good. That IMHO seems simpler than actually avoiding walking
into *_EXTRA_ARGS from extract_locals_r because we'd have to repeat
the walking logic from cp_walk_subtree modulo the *_EXTRA_ARGS walk.
How does the following look? Bootstraped and regtested on
x86_64-pc-linux-gnu.
-- > 8--
Subject: [PATCH] c++: build_extra_args recapturing local specs [PR114303]
PR c++/114303
gcc/cp/ChangeLog:
* constraint.cc (tsubst_requires_expr): Clear
REQUIRES_EXPR_EXTRA_ARGS before calling build_extra_args.
* pt.cc (extract_locals_r): Assert *_EXTRA_ARGS is empty.
(tsubst_stmt) <case IF_STMT>: Call build_extra_args
on the new IF_STMT instead of t which might already have
IF_STMT_EXTRA_ARGS.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1z/constexpr-if-lambda6.C: New test.
---
gcc/cp/constraint.cc | 1 +
gcc/cp/pt.cc | 16 +++++++++++++++-
.../g++.dg/cpp1z/constexpr-if-lambda6.C | 16 ++++++++++++++++
3 files changed, 32 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
diff --git a/gcc/cp/constraint.cc b/gcc/cp/constraint.cc
index 49de3211d4c..8a3b5d80ba7 100644
--- a/gcc/cp/constraint.cc
+++ b/gcc/cp/constraint.cc
@@ -2362,6 +2362,7 @@ tsubst_requires_expr (tree t, tree args, sat_info info)
matching or dguide constraint rewriting), in which case we need
to partially substitute. */
t = copy_node (t);
+ REQUIRES_EXPR_EXTRA_ARGS (t) = NULL_TREE;
REQUIRES_EXPR_EXTRA_ARGS (t) = build_extra_args (t, args, info.complain);
return t;
}
diff --git a/gcc/cp/pt.cc b/gcc/cp/pt.cc
index c38594cd862..6cc9b95fc06 100644
--- a/gcc/cp/pt.cc
+++ b/gcc/cp/pt.cc
@@ -13310,6 +13310,19 @@ extract_locals_r (tree *tp, int *walk_subtrees, void
*data_)
/* Remember local typedefs (85214). */
tp = &TYPE_NAME (*tp);
+ if (has_extra_args_mechanism_p (*tp))
+ {
+ if (PACK_EXPANSION_P (*tp))
+ gcc_checking_assert (!PACK_EXPANSION_EXTRA_ARGS (*tp));
+ else if (TREE_CODE (*tp) == REQUIRES_EXPR)
+ gcc_checking_assert (!REQUIRES_EXPR_EXTRA_ARGS (*tp));
+ else if (TREE_CODE (*tp) == IF_STMT
+ && IF_STMT_CONSTEXPR_P (*tp))
+ gcc_checking_assert (!IF_STMT_EXTRA_ARGS (*tp));
+ else
+ gcc_unreachable ();
+ }
+
if (TREE_CODE (*tp) == DECL_EXPR)
{
tree decl = DECL_EXPR_DECL (*tp);
@@ -18738,7 +18751,8 @@ tsubst_stmt (tree t, tree args, tsubst_flags_t
complain, tree in_decl)
IF_COND (stmt) = IF_COND (t);
THEN_CLAUSE (stmt) = THEN_CLAUSE (t);
ELSE_CLAUSE (stmt) = ELSE_CLAUSE (t);
- IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (t, args, complain);
+ IF_SCOPE (stmt) = NULL_TREE;
+ IF_STMT_EXTRA_ARGS (stmt) = build_extra_args (stmt, args, complain);
add_stmt (stmt);
break;
}
diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
new file mode 100644
index 00000000000..038c2a41210
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if-lambda6.C
@@ -0,0 +1,16 @@
+// PR c++/114303
+// { dg-do compile { target c++17 } }
+
+struct A { static constexpr bool value = true; };
+
+int main() {
+ [](auto x1) {
+ return [&](auto) {
+ return [&](auto x3) {
+ if constexpr (decltype(x3)::value) {
+ static_assert(decltype(x1)::value);
+ }
+ }(A{});
+ }(0);
+ }(A{});
+}
--
2.44.0.548.g91ec36f2cc
