[PATCH] c++: disallow constinit on functions [PR111173]

[Marek Polacek via Gcc-patches]

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

-- >8 --

[dcl.constinit]/1: The constinit specifier shall be applied only to a 
declaration
of a variable with static or thread storage duration.

and while we detect

  constinit int fn();

we weren't detecting

  using F = int();
  constinit F f;

        PR c++/111173

gcc/cp/ChangeLog:

        * decl.cc (grokdeclarator): Disallow constinit on functions.

gcc/testsuite/ChangeLog:

        * g++.dg/cpp2a/constinit19.C: New test.
---
 gcc/cp/decl.cc                           | 3 +++
 gcc/testsuite/g++.dg/cpp2a/constinit19.C | 5 +++++
 2 files changed, 8 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/constinit19.C

diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index bea0ee92106..a0e8a24efc0 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -14639,6 +14639,9 @@ grokdeclarator (const cp_declarator *declarator,
                        "storage class %<thread_local%> invalid for "
                        "function %qs", name);
          }
+       else if (constinit_p)
+         error_at (declspecs->locations[ds_constinit],
+                   "%<constinit%> specifier invalid for function %qs", name);
 
         if (virt_specifiers)
           error ("virt-specifiers in %qs not allowed outside a class "
diff --git a/gcc/testsuite/g++.dg/cpp2a/constinit19.C 
b/gcc/testsuite/g++.dg/cpp2a/constinit19.C
new file mode 100644
index 00000000000..5be610a18a2
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/constinit19.C
@@ -0,0 +1,5 @@
+// PR c++/111173
+// { dg-do compile { target c++20 } }
+
+using Function = int();
+constinit Function f; // { dg-error ".constinit. specifier invalid for 
function" }

base-commit: fce74ce2535aa3b7648ba82e7e61eb77d0175546
-- 
2.41.0