diff mbox series

c++: fn redecl in fn scope wrongly accepted [PR116239]

Message ID 20240830194018.889736-1-polacek@redhat.com
State New
Headers show
Series c++: fn redecl in fn scope wrongly accepted [PR116239] | expand

Commit Message

Marek Polacek Aug. 30, 2024, 7:40 p.m. UTC
Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

-- >8 --
Redeclaration such as

  void f(void);
  consteval void f(void);

is invalid.  In a namespace scope, we detect the collision in
validate_constexpr_redeclaration, but not when one declaration is
at block scope.

When we have

  void f(void);
  void g() { consteval void f(void); }

we call pushdecl on the second f and call push_local_extern_decl_alias.
It finds the namespace-scope f:

        for (ovl_iterator iter (binding); iter; ++iter)
          if (decls_match (decl, *iter, /*record_versions*/false))
            {
              alias = *iter;
              break;
            }

but decls_match says they match so we just set DECL_LOCAL_DECL_ALIAS
(and do not call another pushdecl leading to duplicate_decls which
would detect mismatching return types, for example).  I don't think
we want to change decls_match, so a simple fix is to detect the
problem in push_local_extern_decl_alias.

	PR c++/116239

gcc/cp/ChangeLog:

	* cp-tree.h (validate_constexpr_redeclaration): Declare.
	* decl.cc (validate_constexpr_redeclaration): No longer static.
	* name-lookup.cc (push_local_extern_decl_alias): Call
	validate_constexpr_redeclaration.

gcc/testsuite/ChangeLog:

	* g++.dg/diagnostic/redeclaration-6.C: New test.
---
 gcc/cp/cp-tree.h                              |  1 +
 gcc/cp/decl.cc                                |  2 +-
 gcc/cp/name-lookup.cc                         |  3 ++
 .../g++.dg/diagnostic/redeclaration-6.C       | 34 +++++++++++++++++++
 4 files changed, 39 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/g++.dg/diagnostic/redeclaration-6.C


base-commit: b222122d4e93de2238041a01b1886c7dfd9944da

Comments

Jason Merrill Sept. 4, 2024, 4:28 p.m. UTC | #1
On 8/30/24 3:40 PM, Marek Polacek wrote:
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> 
> -- >8 --
> Redeclaration such as
> 
>    void f(void);
>    consteval void f(void);
> 
> is invalid.  In a namespace scope, we detect the collision in
> validate_constexpr_redeclaration, but not when one declaration is
> at block scope.
> 
> When we have
> 
>    void f(void);
>    void g() { consteval void f(void); }
> 
> we call pushdecl on the second f and call push_local_extern_decl_alias.
> It finds the namespace-scope f:
> 
>          for (ovl_iterator iter (binding); iter; ++iter)
>            if (decls_match (decl, *iter, /*record_versions*/false))
>              {
>                alias = *iter;
>                break;
>              }
> 
> but decls_match says they match so we just set DECL_LOCAL_DECL_ALIAS
> (and do not call another pushdecl leading to duplicate_decls which
> would detect mismatching return types, for example).  I don't think
> we want to change decls_match, so a simple fix is to detect the
> problem in push_local_extern_decl_alias.
> 
> 	PR c++/116239
> 
> gcc/cp/ChangeLog:
> 
> 	* cp-tree.h (validate_constexpr_redeclaration): Declare.
> 	* decl.cc (validate_constexpr_redeclaration): No longer static.
> 	* name-lookup.cc (push_local_extern_decl_alias): Call
> 	validate_constexpr_redeclaration.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/diagnostic/redeclaration-6.C: New test.
> ---
>   gcc/cp/cp-tree.h                              |  1 +
>   gcc/cp/decl.cc                                |  2 +-
>   gcc/cp/name-lookup.cc                         |  3 ++
>   .../g++.dg/diagnostic/redeclaration-6.C       | 34 +++++++++++++++++++
>   4 files changed, 39 insertions(+), 1 deletion(-)
>   create mode 100644 gcc/testsuite/g++.dg/diagnostic/redeclaration-6.C
> 
> diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
> index 2eeb5e3e8b1..1a763b683de 100644
> --- a/gcc/cp/cp-tree.h
> +++ b/gcc/cp/cp-tree.h
> @@ -6992,6 +6992,7 @@ extern bool member_like_constrained_friend_p	(tree);
>   extern bool fns_correspond			(tree, tree);
>   extern int decls_match				(tree, tree, bool = true);
>   extern bool maybe_version_functions		(tree, tree, bool);
> +extern bool validate_constexpr_redeclaration	(tree, tree);
>   extern bool merge_default_template_args		(tree, tree, bool);
>   extern tree duplicate_decls			(tree, tree,
>   						 bool hiding = false,
> diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
> index 6458e96bded..4ad68d609d7 100644
> --- a/gcc/cp/decl.cc
> +++ b/gcc/cp/decl.cc
> @@ -1412,7 +1412,7 @@ check_redeclaration_exception_specification (tree new_decl,
>   /* Return true if OLD_DECL and NEW_DECL agree on constexprness.
>      Otherwise issue diagnostics.  */
>   
> -static bool
> +bool
>   validate_constexpr_redeclaration (tree old_decl, tree new_decl)
>   {
>     old_decl = STRIP_TEMPLATE (old_decl);
> diff --git a/gcc/cp/name-lookup.cc b/gcc/cp/name-lookup.cc
> index 70ad4cbf3b5..6777d97ac2e 100644
> --- a/gcc/cp/name-lookup.cc
> +++ b/gcc/cp/name-lookup.cc
> @@ -3708,6 +3708,9 @@ push_local_extern_decl_alias (tree decl)
>   	}
>       }
>   
> +  if (!validate_constexpr_redeclaration (alias, decl))
> +    return;
> +
>     retrofit_lang_decl (decl);
>     DECL_LOCAL_DECL_ALIAS (decl) = alias;
>   }

I don't think we need this in the case that we built a new alias and 
pushed it; in that case alias is built from decl, and should certainly 
match already.  So let's put this call before we decide to build a new 
alias, either in the loop or just after it.

Jason
diff mbox series

Patch

diff --git a/gcc/cp/cp-tree.h b/gcc/cp/cp-tree.h
index 2eeb5e3e8b1..1a763b683de 100644
--- a/gcc/cp/cp-tree.h
+++ b/gcc/cp/cp-tree.h
@@ -6992,6 +6992,7 @@  extern bool member_like_constrained_friend_p	(tree);
 extern bool fns_correspond			(tree, tree);
 extern int decls_match				(tree, tree, bool = true);
 extern bool maybe_version_functions		(tree, tree, bool);
+extern bool validate_constexpr_redeclaration	(tree, tree);
 extern bool merge_default_template_args		(tree, tree, bool);
 extern tree duplicate_decls			(tree, tree,
 						 bool hiding = false,
diff --git a/gcc/cp/decl.cc b/gcc/cp/decl.cc
index 6458e96bded..4ad68d609d7 100644
--- a/gcc/cp/decl.cc
+++ b/gcc/cp/decl.cc
@@ -1412,7 +1412,7 @@  check_redeclaration_exception_specification (tree new_decl,
 /* Return true if OLD_DECL and NEW_DECL agree on constexprness.
    Otherwise issue diagnostics.  */
 
-static bool
+bool
 validate_constexpr_redeclaration (tree old_decl, tree new_decl)
 {
   old_decl = STRIP_TEMPLATE (old_decl);
diff --git a/gcc/cp/name-lookup.cc b/gcc/cp/name-lookup.cc
index 70ad4cbf3b5..6777d97ac2e 100644
--- a/gcc/cp/name-lookup.cc
+++ b/gcc/cp/name-lookup.cc
@@ -3708,6 +3708,9 @@  push_local_extern_decl_alias (tree decl)
 	}
     }
 
+  if (!validate_constexpr_redeclaration (alias, decl))
+    return;
+
   retrofit_lang_decl (decl);
   DECL_LOCAL_DECL_ALIAS (decl) = alias;
 }
diff --git a/gcc/testsuite/g++.dg/diagnostic/redeclaration-6.C b/gcc/testsuite/g++.dg/diagnostic/redeclaration-6.C
new file mode 100644
index 00000000000..ed8d4af7792
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/redeclaration-6.C
@@ -0,0 +1,34 @@ 
+// PR c++/116239
+// { dg-do compile { target c++20 } }
+
+consteval void f1();
+void f2();
+constexpr void f3();
+void f4();
+consteval void f5();
+constexpr void f6();
+
+void
+g ()
+{
+  void f1();		// { dg-error "differs in .consteval." }
+  consteval void f2();	// { dg-error "differs in .consteval." }
+
+  void f3();		// { dg-error "differs in .constexpr." }
+  constexpr void f4();  // { dg-error "differs in .constexpr." }
+
+  consteval void f5();
+  constexpr void f6();
+
+  void f7();
+  consteval void f7();	// { dg-error "differs in .consteval." }
+
+  consteval void f8();
+  void f8();		// { dg-error "differs in .consteval." }
+
+  void f9();
+  constexpr void f9();	// { dg-error "differs in .constexpr." }
+
+  constexpr void f10();
+  void f10();		// { dg-error "differs in .constexpr." }
+}