From: Marek Polacek <polacek@redhat.com>
To: Jason Merrill <jason@redhat.com>, GCC Patches <gcc-patches@gcc.gnu.org>
Cc: Jakub Jelinek <jakub@redhat.com>
Subject: [PATCH] c++: constexpr error with fn redecl in local scope [PR111132]
Date: Tue, 2 Apr 2024 13:52:37 -0400 [thread overview]
Message-ID: <20240402175237.482119-1-polacek@redhat.com> (raw)
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk/13?
-- >8 --
We evaluate constexpr functions on the original, pre-genericization bodies.
That means that the function body we're evaluating will not have gone
through cp_genericize_r's "Map block scope extern declarations to visible
declarations with the same name and type in outer scopes if any". Here:
constexpr bool bar() { return true; } // #1
constexpr bool foo() {
constexpr bool bar(void); // #2
return bar();
}
it means that we:
1) register_constexpr_fundef (#1)
2) cp_genericize (#1)
nothing interesting happens
3) register_constexpr_fundef (foo)
does copy_fn, so we have two copies of the BIND_EXPR
4) cp_genericize (foo)
this remaps #2 to #1, but only on one copy of the BIND_EXPR
5) retrieve_constexpr_fundef (foo)
we find it, no problem
6) retrieve_constexpr_fundef (#2)
and here #2 isn't found in constexpr_fundef_table, because
we're working on the BIND_EXPR copy where #2 wasn't mapped to #1
so we fail. We've only registered #1.
It should work to use DECL_LOCAL_DECL_ALIAS (which used to be
extern_decl_map). We evaluate constexpr functions on pre-cp_fold
bodies to avoid diagnostic problems, but the remapping I'm proposing
should not interfere with diagnostics.
This is not a problem for a global scope redeclaration; there we go
through duplicate_decls which keeps the DECL_UID:
DECL_UID (olddecl) = olddecl_uid;
and DECL_UID is what constexpr_fundef_hasher::hash uses.
PR c++/111132
gcc/cp/ChangeLog:
* constexpr.cc (get_function_named_in_call): If there's
a DECL_LOCAL_DECL_ALIAS, use it.
gcc/testsuite/ChangeLog:
* g++.dg/cpp0x/constexpr-redeclaration3.C: New test.
* g++.dg/cpp0x/constexpr-redeclaration4.C: New test.
---
gcc/cp/constexpr.cc | 19 +++++++++++++++----
.../g++.dg/cpp0x/constexpr-redeclaration3.C | 13 +++++++++++++
.../g++.dg/cpp0x/constexpr-redeclaration4.C | 14 ++++++++++++++
3 files changed, 42 insertions(+), 4 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration3.C
create mode 100644 gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration4.C
diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index fa346fe01c9..b47f0e984c0 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -702,15 +702,26 @@ build_constexpr_constructor_member_initializers (tree type, tree body)
/* We have an expression tree T that represents a call, either CALL_EXPR
or AGGR_INIT_EXPR. If the call is lexically to a named function,
- retrun the _DECL for that function. */
+ return the _DECL for that function. */
static tree
get_function_named_in_call (tree t)
{
tree fun = cp_get_callee (t);
- if (fun && TREE_CODE (fun) == ADDR_EXPR
- && TREE_CODE (TREE_OPERAND (fun, 0)) == FUNCTION_DECL)
- fun = TREE_OPERAND (fun, 0);
+ if (fun)
+ {
+ if (TREE_CODE (fun) == ADDR_EXPR
+ && TREE_CODE (TREE_OPERAND (fun, 0)) == FUNCTION_DECL)
+ fun = TREE_OPERAND (fun, 0);
+ /* We evaluate constexpr functions on the original, pre-genericization
+ bodies. So block-scope extern declarations have not been mapped to
+ declarations in outer scopes. Use the namespace-scope declaration,
+ if any, so that retrieve_constexpr_fundef can find it (PR111132). */
+ if (TREE_CODE (fun) == FUNCTION_DECL && DECL_LOCAL_DECL_P (fun))
+ if (tree alias = DECL_LOCAL_DECL_ALIAS (fun))
+ if (alias != error_mark_node)
+ fun = alias;
+ }
return fun;
}
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration3.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration3.C
new file mode 100644
index 00000000000..2b41b456fc3
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration3.C
@@ -0,0 +1,13 @@
+// PR c++/111132
+// { dg-do compile { target c++11 } }
+
+constexpr bool bar(void) {
+ return true;
+}
+
+constexpr bool foo() {
+ constexpr bool bar(void);
+ return bar();
+}
+
+static_assert(foo(), "");
diff --git a/gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration4.C b/gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration4.C
new file mode 100644
index 00000000000..c58247218c6
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/constexpr-redeclaration4.C
@@ -0,0 +1,14 @@
+// PR c++/111132
+// { dg-do compile { target c++11 } }
+
+constexpr bool bar(void) {
+ return true;
+}
+
+constexpr bool bar(void);
+
+constexpr bool foo() {
+ return bar();
+}
+
+static_assert(foo(), "");
base-commit: 0e64bbb8823f7b3757befc878ed177dfb59943d1
--
2.44.0
next reply other threads:[~2024-04-02 17:52 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-02 17:52 Marek Polacek [this message]
2024-04-03 17:14 ` Jason Merrill
2024-04-04 18:43 ` Marek Polacek
2024-04-04 21:28 ` Jason Merrill
2024-04-04 23:15 ` [PATCH v2] " Marek Polacek
2024-04-05 3:56 ` Jason Merrill
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