Here, the problem was that extract_local_specs wasn't seeing that we use
'self' inside the lambda in the else of the inner constexpr if, because we
don't walk into lambda bodies and we didn't capture it in the lambda because
'self' is still dependent. Marek recently changed process_outer_var_ref to
do more implicit capture in templates; this example shows that we should
always capture non-packs, so that we can continue to not walk into lambda
bodies. We do walk into lambda bodies for pack expansions, so we can delay
deciding whether we're capturing a single element or the entire pack.
Immediately capturing a VLA means we need to create a dependent VLA capture
type, and not in the context of the lambda op(), since trying to look up the
instantiation of the op() while we're substituting into the capture list
would crash. So I force TYPE_CONTEXT and the binding level out to the
enclosing function before pushtag, avoid adding a TAG_DEFN, and instead
force the type to be complete in tsubst_lambda_expr.
Tested x86_64-pc-linux-gnu, applying to trunk.
* semantics.c (process_outer_var_ref): Do capture dependent vars.
* class.c (finish_struct): Only add TAG_DEFN if T is in
current_function_decl.
* lambda.c (vla_capture_type): Force the capture type out into the
lambda's enclosing function.
(add_capture): Pass in the lambda.
* pt.c (tsubst_lambda_expr): complete_type a VLA capture type.
---
gcc/cp/class.c | 1 +
gcc/cp/lambda.c | 28 ++++++++++++++++++---
gcc/cp/pt.c | 4 +++
gcc/cp/semantics.c | 8 +++---
gcc/testsuite/g++.dg/cpp1z/constexpr-if27.C | 22 ++++++++++++++++
gcc/cp/ChangeLog | 11 ++++++++
6 files changed, 68 insertions(+), 6 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp1z/constexpr-if27.C
diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index f44acfd62b5..830ede56af8 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -7246,6 +7246,7 @@ finish_struct (tree t, tree attributes)
error ("trying to finish struct, but kicked out due to previous parse
errors");
if (processing_template_decl && at_function_scope_p ()
+ && TYPE_CONTEXT (t) == current_function_decl
/* Lambdas are defined by the LAMBDA_EXPR. */
&& !LAMBDA_TYPE_P (t))
add_stmt (build_min (TAG_DEFN, t));
diff --git a/gcc/cp/lambda.c b/gcc/cp/lambda.c
index d178f15a4da..c25df2fbc0e 100644
--- a/gcc/cp/lambda.c
+++ b/gcc/cp/lambda.c
@@ -479,9 +479,31 @@ static GTY(()) tree max_id;
an array of runtime length. */
static tree
-vla_capture_type (tree array_type)
+vla_capture_type (tree array_type, tree lambda)
{
- tree type = xref_tag (record_type, make_anon_name (), ts_current, false);
+ tree closure = LAMBDA_EXPR_CLOSURE (lambda);
+ tree type = make_class_type (RECORD_TYPE);
+ cp_binding_level *slev = current_binding_level;
+ if (closure)
+ {
+ /* If we're already inside the lambda body, force the capture type out
+ into the enclosing context, so we don't crash trying to instantiate
+ the capture field in tsubst_lambda_expr. We won't have a TAG_DEFN
+ from finish_struct in the enclosing context, which we work around in
+ tsubst_lambda_expr. */
+ TYPE_CONTEXT (type) = TYPE_CONTEXT (closure);
+ cp_binding_level *b = current_binding_level;
+ for (;; b = b->level_chain)
+ if (b->this_entity == closure)
+ {
+ while (b->this_entity == closure)
+ b = b->level_chain;
+ break;
+ }
+ current_binding_level = b;
+ }
+ type = pushtag (make_anon_name (), type, ts_current);
+ current_binding_level = slev;
xref_basetypes (type, NULL_TREE);
type = begin_class_definition (type);
if (!ptr_id)
@@ -541,7 +563,7 @@ add_capture (tree lambda, tree id, tree orig_init, bool
by_reference_p,
initializer = build_constructor_va (init_list_type_node, 2,
NULL_TREE, build_address (elt),
NULL_TREE, array_type_nelts (type));
- type = vla_capture_type (type);
+ type = vla_capture_type (type, lambda);
}
else if (!dependent_type_p (type)
&& variably_modified_type_p (type, NULL_TREE))
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index d678e278078..673ea8e2258 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -17989,6 +17989,10 @@ tsubst_lambda_expr (tree t, tree args, tsubst_flags_t
complain, tree in_decl)
if (PACK_EXPANSION_P (ofield))
ofield = PACK_EXPANSION_PATTERN (ofield);
tree field = tsubst_decl (ofield, args, complain);
+ if (DECL_VLA_CAPTURE_P (ofield))
+ /* The type of a VLA capture might not have a TAG_DEFN in the enclosing
+ context, so complete it here. */
+ complete_type (TREE_TYPE (field));
if (DECL_PACK_P (ofield) && !DECL_NORMAL_CAPTURE_P (ofield))
{
diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index da814bdd655..d1a378acd98 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -3469,10 +3469,12 @@ process_outer_var_ref (tree decl, tsubst_flags_t
complain, bool odr_use)
= decl_function_context (containing_function);
}
- /* In a lambda within a template, wait until instantiation
- time to implicitly capture a dependent type. */
+ /* In a lambda within a template, wait until instantiation time to implicitly
+ capture a parameter pack. We want to wait because we don't know if we're
+ capturing the whole pack or a single element, and it's OK to wait because
+ find_parameter_packs_r walks into the lambda body. */
if (context == containing_function
- && dependent_type_p (TREE_TYPE (decl)))
+ && DECL_PACK_P (decl))
return decl;
if (lambda_expr && VAR_P (decl)
diff --git a/gcc/testsuite/g++.dg/cpp1z/constexpr-if27.C
b/gcc/testsuite/g++.dg/cpp1z/constexpr-if27.C
new file mode 100644
index 00000000000..a1a6e0b78f6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/constexpr-if27.C
@@ -0,0 +1,22 @@
+// PR c++/86969
+// { dg-do compile { target c++17 } }
+
+auto compose = [](auto... fs) {
+ if constexpr (sizeof...(fs) == 0) {
+ return [](auto x) { return x; };
+ } else {
+ auto fn = [](auto self, auto f, auto... fs) {
+ if constexpr (sizeof...(fs) == 0) return f;
+ else return [=](auto x) {
+ return f(self(self, fs...)(x));
+ };
+ };
+ return fn(fn, fs...);
+ }
+};
+
+static_assert(compose(
+ [](auto x) { return x * 3; },
+ [](auto x) { return x + 1; },
+ [](auto x) { return x / 2; }
+ )(6) == 12);
diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index a2d16e15b4a..e4d876b4c0b 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,14 @@
+2019-02-27 Jason Merrill <ja...@redhat.com>
+
+ PR c++/86969 - ICE with constexpr if and recursive generic lambdas.
+ * semantics.c (process_outer_var_ref): Do capture dependent vars.
+ * class.c (finish_struct): Only add TAG_DEFN if T is in
+ current_function_decl.
+ * lambda.c (vla_capture_type): Force the capture type out into the
+ lambda's enclosing function.
+ (add_capture): Pass in the lambda.
+ * pt.c (tsubst_lambda_expr): complete_type a VLA capture type.
+
2019-02-27 Marek Polacek <pola...@redhat.com>
PR c++/89511 - ICE with using-declaration and unscoped enumerator.
base-commit: c70a6d7d64938ac4d2fe4b6364819b1cffd5c136
--
2.20.1
