On 6/11/26 12:28 PM, Marek Polacek wrote:
On Wed, Jun 10, 2026 at 06:06:23PM -0400, Jason Merrill wrote:
On 6/10/26 3:48 PM, Marek Polacek wrote:
On Tue, Jun 09, 2026 at 04:22:38PM -0400, Jason Merrill wrote:
On 6/4/26 6:26 PM, Marek Polacek wrote:
On Thu, Jun 04, 2026 at 05:20:30PM -0400, Jason Merrill wrote:
On 6/4/26 3:39 PM, Marek Polacek wrote:
On Wed, Jun 03, 2026 at 03:41:56PM -0400, Jason Merrill wrote:
On 6/2/26 5:59 PM, Marek Polacek wrote:
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/branches?
-- >8 --
Here we crash because a TARGET_EXPR gets into tsubst_expr with something
like:
template<typename>
constexpr static A a = (A{}, A{});
Pre r14-4796, when we had tsubst_copy, we didn't crash because we had
an early exit when substituting with args=NULL_TREE. tsubst_expr
deliberately doesn't have that early exit.
Note that
template<typename>
constexpr static A a = A{};
works because expand_aggr_init_1 sees a COMPOUND_LITERAL_P and does the
early exit without calling expand_default_init. But with a COMPOUND_EXPR
we don't take that path.
The TARGET_EXPR is created via check_initializer -> build_aggr_init_full_exprs
-> build_aggr_init -> expand_aggr_init_1 -> expand_default_init -> ocp_convert
-> build_cplus_new -> build_target_expr. I tried adjusting the big
and ugly check in check_initializer before build_aggr_init_full_exprs
but that didn't work out. I also tried avoiding the call to ocp_convert
but that broke some reflection tests. But avoiding the call to
build_cplus_new seems to work.
PR c++/125539
gcc/cp/ChangeLog:
* cvt.cc (ocp_convert): Don't call build_cplus_new in a
template.
I notice that build_aggr_init_expr already shortcuts
processing_template_decl. What if we do that in build_cplus_new as well, if
init has the right type?
I think that looks better, and is a more general fix.
dg.exp passed; ok for trunk/branches if the rest of the testing passes too?
-- >8 --
Here we crash because a TARGET_EXPR gets into tsubst_expr with something
like:
template<typename>
constexpr static A a = (A{}, A{});
Pre r14-4796, when we had tsubst_copy, we didn't crash because we had
an early exit when substituting with args=NULL_TREE. tsubst_expr
deliberately doesn't have that early exit.
Note that
template<typename>
constexpr static A a = A{};
works because expand_aggr_init_1 sees a COMPOUND_LITERAL_P and does the
early exit without calling expand_default_init. But with a COMPOUND_EXPR
we don't take that path.
The TARGET_EXPR is created via check_initializer -> build_aggr_init_full_exprs
-> build_aggr_init -> expand_aggr_init_1 -> expand_default_init -> ocp_convert
-> build_cplus_new -> build_target_expr. I tried adjusting the big
and ugly check in check_initializer before build_aggr_init_full_exprs
but that didn't work out. I also tried avoiding the call to ocp_convert
but that broke some reflection tests.
We can fix this by returning early in build_cplus_new in a template,
like in build_aggr_init_expr.
PR c++/125539
gcc/cp/ChangeLog:
* tree.cc (build_cplus_new): In a template, return before creating
a TARGET_EXPR.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1y/var-templ89.C: New test.
---
gcc/cp/tree.cc | 5 ++++
gcc/testsuite/g++.dg/cpp1y/var-templ89.C | 32 ++++++++++++++++++++++++
2 files changed, 37 insertions(+)
create mode 100644 gcc/testsuite/g++.dg/cpp1y/var-templ89.C
diff --git a/gcc/cp/tree.cc b/gcc/cp/tree.cc
index 360eae87698..df9dd562314 100644
--- a/gcc/cp/tree.cc
+++ b/gcc/cp/tree.cc
@@ -838,6 +838,11 @@ build_cplus_new (tree type, tree init, tsubst_flags_t
complain)
if (abstract_virtuals_error (NULL_TREE, type, complain))
return error_mark_node;
+ /* As in build_aggr_init_expr. We don't want to create a TARGET_EXPR
+ in a template. */
+ if (processing_template_decl)
+ return rval;
I mentioned "if init has the right type"; we need to check that so we don't
just return a void constructor call.
Oop, now I see what you meant, sorry.
If I check
if (processing_template_decl
&& same_type_ignoring_top_level_qualifiers_p (type, TREE_TYPE (init)))
return rval;
then we crash on var-templ89.C with -std=c++14 because we don't
elide the copy, so have a ctor call, so the types don't match, so
we create a TARGET_EXPR.
Ah, well. So I guess shortcutting the template case in ocp_convert, but
again returning the constructor call is wrong; perhaps we should take the
earlier perform_implicit_conversion route in a template?
Thanks. Maybe something like this, then?
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/branches?
-- >8 --
Here we crash because a TARGET_EXPR gets into tsubst_expr with something
like:
template<typename>
constexpr static A a = (A{}, A{});
Pre r14-4796, when we had tsubst_copy, we didn't crash because we had
an early exit when substituting with args=NULL_TREE. tsubst_expr
deliberately doesn't have that early exit.
Note that
template<typename>
constexpr static A a = A{};
works because expand_aggr_init_1 sees a COMPOUND_LITERAL_P and does the
early exit without calling expand_default_init. But with a COMPOUND_EXPR
we don't take that path.
The TARGET_EXPR is created via check_initializer -> build_aggr_init_full_exprs
-> build_aggr_init -> expand_aggr_init_1 -> expand_default_init -> ocp_convert
-> build_cplus_new -> build_target_expr. I tried adjusting the big
and ugly check in check_initializer before build_aggr_init_full_exprs
but that didn't work out. I also tried avoiding the call to ocp_convert
but that broke some reflection tests.
We can fix this by calling perform_implicit_conversion in a template to
create an IMPLICIT_CONV_EXPR, then build_cplus_new won't create a TARGET_EXPR.
PR c++/125539
gcc/cp/ChangeLog:
* cvt.cc (ocp_convert): In a template, always call
perform_implicit_conversion.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1y/var-templ89.C: New test.
---
gcc/cp/cvt.cc | 5 +++-
gcc/testsuite/g++.dg/cpp1y/var-templ89.C | 32 ++++++++++++++++++++++++
2 files changed, 36 insertions(+), 1 deletion(-)
create mode 100644 gcc/testsuite/g++.dg/cpp1y/var-templ89.C
diff --git a/gcc/cp/cvt.cc b/gcc/cp/cvt.cc
index b1176317d99..d5a64e098d2 100644
--- a/gcc/cp/cvt.cc
+++ b/gcc/cp/cvt.cc
@@ -968,7 +968,10 @@ ocp_convert (tree type, tree expr, int convtype, int flags,
if (abstract_virtuals_error (NULL_TREE, type, complain))
return error_mark_node;
- if (BRACE_ENCLOSED_INITIALIZER_P (ctor))
+ if (BRACE_ENCLOSED_INITIALIZER_P (ctor)
+ /* We don't want to create a TARGET_EXPR in a template by the
+ build_cplus_new below. */
+ || processing_template_decl)
ctor = perform_implicit_conversion (type, ctor, complain);
I think this should be perform_implicit_conversion_flags now.
Ok, though nothing triggers the case where flags != LOOKUP_IMPLICIT.
With this patch do we still need this in check_initializer?
=> if (processing_template_decl && TREE_CODE (rhs) == TARGET_EXPR)
/* Avoid leaking TARGET_EXPR into template trees. */
rhs = build_implicit_conv_flags (type, init, flags);
Nothing breaks if I remove the whole thing.
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/branches?
OK.
-- >8 --
Here we crash because a TARGET_EXPR gets into tsubst_expr with something
like:
template<typename>
constexpr static A a = (A{}, A{});
Pre r14-4796, when we had tsubst_copy, we didn't crash because we had
an early exit when substituting with args=NULL_TREE. tsubst_expr
deliberately doesn't have that early exit.
Note that
template<typename>
constexpr static A a = A{};
works because expand_aggr_init_1 sees a COMPOUND_LITERAL_P and does the
early exit without calling expand_default_init. But with a COMPOUND_EXPR
we don't take that path.
The TARGET_EXPR is created via check_initializer -> build_aggr_init_full_exprs
-> build_aggr_init -> expand_aggr_init_1 -> expand_default_init -> ocp_convert
-> build_cplus_new -> build_target_expr. I tried adjusting the big
and ugly check in check_initializer before build_aggr_init_full_exprs
but that didn't work out. I also tried avoiding the call to ocp_convert
but that broke some reflection tests.
We can fix this by calling perform_implicit_conversion in a template to
create an IMPLICIT_CONV_EXPR, then build_cplus_new won't create a TARGET_EXPR.
PR c++/125539
gcc/cp/ChangeLog:
* cvt.cc (ocp_convert): In a template, always call
perform_implicit_conversion. Pass flags to
perform_implicit_conversion_flags.
* decl.cc (check_initializer): Remove a call to
build_implicit_conv_flags.
gcc/testsuite/ChangeLog:
* g++.dg/cpp1y/var-templ89.C: New test.
---
gcc/cp/cvt.cc | 7 ++++--
gcc/cp/decl.cc | 7 +-----
gcc/testsuite/g++.dg/cpp1y/var-templ89.C | 32 ++++++++++++++++++++++++
3 files changed, 38 insertions(+), 8 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp1y/var-templ89.C
diff --git a/gcc/cp/cvt.cc b/gcc/cp/cvt.cc
index b1176317d99..b18f66e582f 100644
--- a/gcc/cp/cvt.cc
+++ b/gcc/cp/cvt.cc
@@ -968,8 +968,11 @@ ocp_convert (tree type, tree expr, int convtype, int flags,
if (abstract_virtuals_error (NULL_TREE, type, complain))
return error_mark_node;
- if (BRACE_ENCLOSED_INITIALIZER_P (ctor))
- ctor = perform_implicit_conversion (type, ctor, complain);
+ if (BRACE_ENCLOSED_INITIALIZER_P (ctor)
+ /* We don't want to create a TARGET_EXPR in a template by the
+ build_cplus_new below. */
+ || processing_template_decl)
+ ctor = perform_implicit_conversion_flags (type, ctor, complain, flags);
else if ((flags & LOOKUP_ONLYCONVERTING)
&& ! (CLASS_TYPE_P (dtype) && DERIVED_FROM_P (type, dtype)))
/* For copy-initialization, first we create a temp of the proper type
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index cba85c959ff..23f23b39544 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -8625,12 +8625,7 @@ check_initializer (tree decl, tree init, int flags,
vec<tree, va_gc> **cleanups)
/* In C++20, the call to build_aggr_init could have created
an INIT_EXPR with a CONSTRUCTOR as the RHS to handle
A(1, 2). */
- tree rhs = TREE_OPERAND (init_code, 1);
- if (processing_template_decl && TREE_CODE (rhs) == TARGET_EXPR)
- /* Avoid leaking TARGET_EXPR into template trees. */
- rhs = build_implicit_conv_flags (type, init, flags);
- init = rhs;
-
+ init = TREE_OPERAND (init_code, 1);
init_code = NULL_TREE;
/* Don't call digest_init; it's unnecessary and will complain
about aggregate initialization of non-aggregate classes. */
diff --git a/gcc/testsuite/g++.dg/cpp1y/var-templ89.C
b/gcc/testsuite/g++.dg/cpp1y/var-templ89.C
new file mode 100644
index 00000000000..5f98a95580c
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/var-templ89.C
@@ -0,0 +1,32 @@
+// PR c++/125539
+// { dg-do compile { target c++14 } }
+
+struct A {};
+struct B { int i; };
+constexpr void foo () {}
+
+template<typename T>
+constexpr static A a1 = (foo (), A {});
+template<typename T>
+constexpr static A a2 = (A{}, A{});
+template<typename T>
+constexpr static A a3 = A{};
+template<typename T>
+constexpr static A a4 = {};
+template<typename T>
+constexpr static A a5{};
+template<typename T>
+constexpr static A a6 = (A{}, A{}, A{}, A{}, A{}, A{}, A{});
+template<int N>
+constexpr static B b1 = B{N};
+template<int N>
+constexpr static B b2 = (B{N}, B{N});
+
+template const A a1<int>;
+template const A a2<int>;
+template const A a3<int>;
+template const A a4<int>;
+template const A a5<int>;
+template const A a6<int>;
+template const B b1<42>;
+template const B b2<42>;
base-commit: cd52e71e8aea258342deca45868bf2529d4fdd76
