[PATCH] c++: implicit move with throw [PR113853]

[PATCH] c++: implicit move with throw [PR113853]

[Marek Polacek]

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

-- >8 --
Here we have

  template<class T>
  auto is_throwable(T t) -> decltype(throw t, true) { ... }

where we didn't properly mark 't' as IMPLICIT_RVALUE_P, which caused
the wrong overload to have been chosen.  Jason figured out it's because
we don't correctly implement [expr.prim.id.unqual]#4.2, which post-P2266
says that an id-expression is move-eligible if

"the id-expression (possibly parenthesized) is the operand of
a throw-expression, and names an implicitly movable entity that belongs
to a scope that does not contain the compound-statement of the innermost
lambda-expression, try-block, or function-try-block (if any) whose
compound-statement or ctor-initializer contains the throw-expression."

I worked out that it's trying to say that given

  struct X {
    X();
    X(const X&);
    X(X&&) = delete;
  };

the following should fail: the scope of the throw is an sk_try, and it's
also x's scope S, and S "does not contain the compound-statement of the
*try-block" so x is move-eligible, so we move, so we fail.

  void f ()
  try {
    X x;
    throw x;  // use of deleted function
  } catch (...) {
  }

Whereas here:

  void g (X x)
  try {
    throw x;
  } catch (...) {
  }

the throw is again in an sk_try, but x's scope is an sk_function_parms
which *does* contain the {} of the *try-block, so x is not move-eligible,
so we don't move, so we use X(const X&), and the code is fine.

The current code also doesn't seem to handle

  void h (X x) {
    void z (decltype(throw x, true));
  }

where there's no enclosing lambda or sk_try so we should move.

I'm not doing anything about lambdas because we shouldn't reach the
code at the end of the function: the DECL_HAS_VALUE_EXPR_P check
shouldn't let us go further.

	PR c++/113789
	PR c++/113853

gcc/cp/ChangeLog:

	* typeck.cc (treat_lvalue_as_rvalue_p): Update code to better
	reflect [expr.prim.id.unqual]#4.2.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/sfinae69.C: Remove dg-bogus.
	* g++.dg/cpp0x/sfinae70.C: New test.
	* g++.dg/cpp0x/sfinae71.C: New test.
	* g++.dg/cpp0x/sfinae72.C: New test.
	* g++.dg/cpp2a/implicit-move4.C: New test.
---
 gcc/cp/typeck.cc                            | 32 +++++------
 gcc/testsuite/g++.dg/cpp0x/sfinae69.C       |  2 +-
 gcc/testsuite/g++.dg/cpp0x/sfinae70.C       | 16 ++++++
 gcc/testsuite/g++.dg/cpp0x/sfinae71.C       | 17 ++++++
 gcc/testsuite/g++.dg/cpp0x/sfinae72.C       | 17 ++++++
 gcc/testsuite/g++.dg/cpp2a/implicit-move4.C | 59 +++++++++++++++++++++
 6 files changed, 126 insertions(+), 17 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae70.C
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae71.C
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae72.C
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/implicit-move4.C

diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 132c55cfc6d..0dc44cd87ca 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -10837,37 +10837,37 @@ treat_lvalue_as_rvalue_p (tree expr, bool return_p)
      parenthesized) id-expression that names an implicitly movable entity
      declared in the body or parameter-declaration-clause of the innermost
      enclosing function or lambda-expression, */
-  if (DECL_CONTEXT (retval) != current_function_decl)
-    return NULL_TREE;
   if (return_p)
     {
+      if (DECL_CONTEXT (retval) != current_function_decl)
+	return NULL_TREE;
       expr = move (expr);
       if (expr == error_mark_node)
 	return NULL_TREE;
       return set_implicit_rvalue_p (expr);
     }
 
-  /* if the operand of a throw-expression is a (possibly parenthesized)
-     id-expression that names an implicitly movable entity whose scope does not
-     extend beyond the compound-statement of the innermost try-block or
-     function-try-block (if any) whose compound-statement or ctor-initializer
-     encloses the throw-expression, */
+  /* if the id-expression (possibly parenthesized) is the operand of
+     a throw-expression, and names an implicitly movable entity that belongs
+     to a scope that does not contain the compound-statement of the innermost
+     lambda-expression, try-block, or function-try-block (if any) whose
+     compound-statement or ctor-initializer contains the throw-expression.  */
 
   /* C++20 added move on throw of parms.  */
   if (TREE_CODE (retval) == PARM_DECL && cxx_dialect < cxx20)
     return NULL_TREE;
 
   for (cp_binding_level *b = current_binding_level;
-       ; b = b->level_chain)
-    {
-      for (tree decl = b->names; decl; decl = TREE_CHAIN (decl))
-	if (decl == retval)
-	  return set_implicit_rvalue_p (move (expr));
-      if (b->kind == sk_function_parms
-	  || b->kind == sk_try
-	  || b->kind == sk_namespace)
+       b->kind != sk_namespace; b = b->level_chain)
+    if (b->kind == sk_try)
+      {
+	for (tree decl = b->names; decl; decl = TREE_CHAIN (decl))
+	  if (decl == retval)
+	    return set_implicit_rvalue_p (move (expr));
 	return NULL_TREE;
-    }
+      }
+
+  return set_implicit_rvalue_p (move (expr));
 }
 
 /* Warn about dubious usage of std::move (in a return statement, if RETURN_P
diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae69.C b/gcc/testsuite/g++.dg/cpp0x/sfinae69.C
index 361e0b79ba2..60eba61165d 100644
--- a/gcc/testsuite/g++.dg/cpp0x/sfinae69.C
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae69.C
@@ -15,7 +15,7 @@ constexpr bool is_throwable(...) { return false; }
 
 constexpr bool b = is_throwable<moveonly>(moveonly{});
 #if __cplusplus >= 202002L
-static_assert (b, "move from the function parameter"); // { dg-bogus "" "PR113853" { xfail c++20 } }
+static_assert (b, "move from the function parameter");
 #else
 static_assert (!b, "no move from the function parameter");
 #endif
diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae70.C b/gcc/testsuite/g++.dg/cpp0x/sfinae70.C
new file mode 100644
index 00000000000..48ea70a61a4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae70.C
@@ -0,0 +1,16 @@
+// PR c++/113789
+// { dg-do compile { target c++11 } }
+
+struct AutoPtr {
+    AutoPtr() = default;
+    AutoPtr(AutoPtr&) {}
+};
+
+template<class T> auto f(T p, int) -> decltype(throw p, 1) = delete;
+template<class T> void f(T p, long);
+
+void
+g ()
+{
+  f (AutoPtr (), 42); // { dg-error "use of deleted function" "" { target c++20_down } }
+}
diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae71.C b/gcc/testsuite/g++.dg/cpp0x/sfinae71.C
new file mode 100644
index 00000000000..2fefe5f70e0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae71.C
@@ -0,0 +1,17 @@
+// PR c++/113789
+// { dg-do compile { target c++11 } }
+// Like sfinae70.C but T&&.
+
+struct AutoPtr {
+    AutoPtr() = default;
+    AutoPtr(AutoPtr&) {}
+};
+
+template<class T> auto f(T&& p, int) -> decltype(throw p, 1) = delete;
+template<class T> void f(T p, long);
+
+void
+g ()
+{
+  f (AutoPtr (), 42); // { dg-error "use of deleted function" "" { target c++20_down } }
+}
diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae72.C b/gcc/testsuite/g++.dg/cpp0x/sfinae72.C
new file mode 100644
index 00000000000..397cdbd8c23
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae72.C
@@ -0,0 +1,17 @@
+// PR c++/113789
+// { dg-do compile { target c++11 } }
+// Like sfinae70.C but ().
+
+struct AutoPtr {
+    AutoPtr() = default;
+    AutoPtr(AutoPtr&) {}
+};
+
+template<class T> auto f(T p, int) -> decltype(throw (p), 1) = delete;
+template<class T> void f(T p, long);
+
+void
+g ()
+{
+  f (AutoPtr (), 42); // { dg-error "use of deleted function" "" { target c++20_down } }
+}
diff --git a/gcc/testsuite/g++.dg/cpp2a/implicit-move4.C b/gcc/testsuite/g++.dg/cpp2a/implicit-move4.C
new file mode 100644
index 00000000000..af4f62e5c7f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/implicit-move4.C
@@ -0,0 +1,59 @@
+// PR c++/113853
+// { dg-do compile { target c++20 } }
+
+struct X {
+  X();
+  X(const X&);
+  X(X&&) = delete;
+};
+
+void
+f1 ()
+{
+  try {
+    ;
+  } catch (X x) {
+    throw x; // { dg-error "use of deleted function" }
+  }
+}
+
+void
+f2 (X x)
+try {
+  ;
+} catch (...) {
+  throw x;  // { dg-error "use of deleted function" }
+}
+
+void
+f3 ()
+try {
+  X x;
+  throw x;  // { dg-error "use of deleted function" }
+} catch (...) {
+}
+
+void
+f4 (X x)
+try {
+  throw x;
+} catch (...) {
+}
+
+void
+f5 (X x)
+{
+  void g (decltype(throw x, true));	// { dg-error "use of deleted function|expected" }
+}
+
+// The "expected" shouldn't be here, c++/113924.
+void
+f6 (X x, int = decltype(throw x, true){}) // { dg-error "use of deleted function|expected" }
+{
+}
+
+void
+f7 (X x)
+{
+  [&] { throw x; };
+}

base-commit: 5459a9074afabf700f055fc8164f88dadb1c39b0
-- 
2.43.0

Re: [PATCH] c++: implicit move with throw [PR113853]

[Jason Merrill]

On 2/15/24 10:19, Marek Polacek wrote:
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> 
> -- >8 --
> Here we have
> 
>    template<class T>
>    auto is_throwable(T t) -> decltype(throw t, true) { ... }
> 
> where we didn't properly mark 't' as IMPLICIT_RVALUE_P, which caused
> the wrong overload to have been chosen.  Jason figured out it's because
> we don't correctly implement [expr.prim.id.unqual]#4.2, which post-P2266
> says that an id-expression is move-eligible if
> 
> "the id-expression (possibly parenthesized) is the operand of
> a throw-expression, and names an implicitly movable entity that belongs
> to a scope that does not contain the compound-statement of the innermost
> lambda-expression, try-block, or function-try-block (if any) whose
> compound-statement or ctor-initializer contains the throw-expression."
> 
> I worked out that it's trying to say that given
> 
>    struct X {
>      X();
>      X(const X&);
>      X(X&&) = delete;
>    };
> 
> the following should fail: the scope of the throw is an sk_try, and it's
> also x's scope S, and S "does not contain the compound-statement of the
> *try-block" so x is move-eligible, so we move, so we fail.
> 
>    void f ()
>    try {
>      X x;
>      throw x;  // use of deleted function
>    } catch (...) {
>    }
> 
> Whereas here:
> 
>    void g (X x)
>    try {
>      throw x;
>    } catch (...) {
>    }
> 
> the throw is again in an sk_try, but x's scope is an sk_function_parms
> which *does* contain the {} of the *try-block, so x is not move-eligible,
> so we don't move, so we use X(const X&), and the code is fine.
> 
> The current code also doesn't seem to handle
> 
>    void h (X x) {
>      void z (decltype(throw x, true));
>    }
> 
> where there's no enclosing lambda or sk_try so we should move.
> 
> I'm not doing anything about lambdas because we shouldn't reach the
> code at the end of the function: the DECL_HAS_VALUE_EXPR_P check
> shouldn't let us go further.
> 
> 	PR c++/113789
> 	PR c++/113853
> 
> gcc/cp/ChangeLog:
> 
> 	* typeck.cc (treat_lvalue_as_rvalue_p): Update code to better
> 	reflect [expr.prim.id.unqual]#4.2.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp0x/sfinae69.C: Remove dg-bogus.
> 	* g++.dg/cpp0x/sfinae70.C: New test.
> 	* g++.dg/cpp0x/sfinae71.C: New test.
> 	* g++.dg/cpp0x/sfinae72.C: New test.
> 	* g++.dg/cpp2a/implicit-move4.C: New test.
> ---
>   gcc/cp/typeck.cc                            | 32 +++++------
>   gcc/testsuite/g++.dg/cpp0x/sfinae69.C       |  2 +-
>   gcc/testsuite/g++.dg/cpp0x/sfinae70.C       | 16 ++++++
>   gcc/testsuite/g++.dg/cpp0x/sfinae71.C       | 17 ++++++
>   gcc/testsuite/g++.dg/cpp0x/sfinae72.C       | 17 ++++++
>   gcc/testsuite/g++.dg/cpp2a/implicit-move4.C | 59 +++++++++++++++++++++
>   6 files changed, 126 insertions(+), 17 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae70.C
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae71.C
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae72.C
>   create mode 100644 gcc/testsuite/g++.dg/cpp2a/implicit-move4.C
> 
> diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
> index 132c55cfc6d..0dc44cd87ca 100644
> --- a/gcc/cp/typeck.cc
> +++ b/gcc/cp/typeck.cc
> @@ -10837,37 +10837,37 @@ treat_lvalue_as_rvalue_p (tree expr, bool return_p)
>        parenthesized) id-expression that names an implicitly movable entity
>        declared in the body or parameter-declaration-clause of the innermost
>        enclosing function or lambda-expression, */
> -  if (DECL_CONTEXT (retval) != current_function_decl)
> -    return NULL_TREE;
>     if (return_p)
>       {
> +      if (DECL_CONTEXT (retval) != current_function_decl)
> +	return NULL_TREE;
>         expr = move (expr);
>         if (expr == error_mark_node)
>   	return NULL_TREE;
>         return set_implicit_rvalue_p (expr);
>       }
>   
> -  /* if the operand of a throw-expression is a (possibly parenthesized)
> -     id-expression that names an implicitly movable entity whose scope does not
> -     extend beyond the compound-statement of the innermost try-block or
> -     function-try-block (if any) whose compound-statement or ctor-initializer
> -     encloses the throw-expression, */
> +  /* if the id-expression (possibly parenthesized) is the operand of
> +     a throw-expression, and names an implicitly movable entity that belongs
> +     to a scope that does not contain the compound-statement of the innermost
> +     lambda-expression, try-block, or function-try-block (if any) whose
> +     compound-statement or ctor-initializer contains the throw-expression.  */

Please also mention here why you aren't checking for lambdas.

>     /* C++20 added move on throw of parms.  */
>     if (TREE_CODE (retval) == PARM_DECL && cxx_dialect < cxx20)
>       return NULL_TREE;
>   
>     for (cp_binding_level *b = current_binding_level;
> -       ; b = b->level_chain)
> -    {
> -      for (tree decl = b->names; decl; decl = TREE_CHAIN (decl))
> -	if (decl == retval)
> -	  return set_implicit_rvalue_p (move (expr));
> -      if (b->kind == sk_function_parms
> -	  || b->kind == sk_try
> -	  || b->kind == sk_namespace)
> +       b->kind != sk_namespace; b = b->level_chain)
> +    if (b->kind == sk_try)
> +      {
> +	for (tree decl = b->names; decl; decl = TREE_CHAIN (decl))
> +	  if (decl == retval)
> +	    return set_implicit_rvalue_p (move (expr));
>   	return NULL_TREE;
> -    }

What if the variable is in a block nested within the try-block?  I think 
we still want to walk b->names for every inner binding level.

Jason

[PATCH v2] c++: implicit move with throw [PR113853]

[Marek Polacek]

On Thu, Feb 15, 2024 at 04:36:40PM -0500, Jason Merrill wrote:
> On 2/15/24 10:19, Marek Polacek wrote:
> > Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
> > 
> > -- >8 --
> > Here we have
> > 
> >    template<class T>
> >    auto is_throwable(T t) -> decltype(throw t, true) { ... }
> > 
> > where we didn't properly mark 't' as IMPLICIT_RVALUE_P, which caused
> > the wrong overload to have been chosen.  Jason figured out it's because
> > we don't correctly implement [expr.prim.id.unqual]#4.2, which post-P2266
> > says that an id-expression is move-eligible if
> > 
> > "the id-expression (possibly parenthesized) is the operand of
> > a throw-expression, and names an implicitly movable entity that belongs
> > to a scope that does not contain the compound-statement of the innermost
> > lambda-expression, try-block, or function-try-block (if any) whose
> > compound-statement or ctor-initializer contains the throw-expression."
> > 
> > I worked out that it's trying to say that given
> > 
> >    struct X {
> >      X();
> >      X(const X&);
> >      X(X&&) = delete;
> >    };
> > 
> > the following should fail: the scope of the throw is an sk_try, and it's
> > also x's scope S, and S "does not contain the compound-statement of the
> > *try-block" so x is move-eligible, so we move, so we fail.
> > 
> >    void f ()
> >    try {
> >      X x;
> >      throw x;  // use of deleted function
> >    } catch (...) {
> >    }
> > 
> > Whereas here:
> > 
> >    void g (X x)
> >    try {
> >      throw x;
> >    } catch (...) {
> >    }
> > 
> > the throw is again in an sk_try, but x's scope is an sk_function_parms
> > which *does* contain the {} of the *try-block, so x is not move-eligible,
> > so we don't move, so we use X(const X&), and the code is fine.
> > 
> > The current code also doesn't seem to handle
> > 
> >    void h (X x) {
> >      void z (decltype(throw x, true));
> >    }
> > 
> > where there's no enclosing lambda or sk_try so we should move.
> > 
> > I'm not doing anything about lambdas because we shouldn't reach the
> > code at the end of the function: the DECL_HAS_VALUE_EXPR_P check
> > shouldn't let us go further.
> > 
> > 	PR c++/113789
> > 	PR c++/113853
> > 
> > gcc/cp/ChangeLog:
> > 
> > 	* typeck.cc (treat_lvalue_as_rvalue_p): Update code to better
> > 	reflect [expr.prim.id.unqual]#4.2.
> > 
> > gcc/testsuite/ChangeLog:
> > 
> > 	* g++.dg/cpp0x/sfinae69.C: Remove dg-bogus.
> > 	* g++.dg/cpp0x/sfinae70.C: New test.
> > 	* g++.dg/cpp0x/sfinae71.C: New test.
> > 	* g++.dg/cpp0x/sfinae72.C: New test.
> > 	* g++.dg/cpp2a/implicit-move4.C: New test.
> > ---
> >   gcc/cp/typeck.cc                            | 32 +++++------
> >   gcc/testsuite/g++.dg/cpp0x/sfinae69.C       |  2 +-
> >   gcc/testsuite/g++.dg/cpp0x/sfinae70.C       | 16 ++++++
> >   gcc/testsuite/g++.dg/cpp0x/sfinae71.C       | 17 ++++++
> >   gcc/testsuite/g++.dg/cpp0x/sfinae72.C       | 17 ++++++
> >   gcc/testsuite/g++.dg/cpp2a/implicit-move4.C | 59 +++++++++++++++++++++
> >   6 files changed, 126 insertions(+), 17 deletions(-)
> >   create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae70.C
> >   create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae71.C
> >   create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae72.C
> >   create mode 100644 gcc/testsuite/g++.dg/cpp2a/implicit-move4.C
> > 
> > diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
> > index 132c55cfc6d..0dc44cd87ca 100644
> > --- a/gcc/cp/typeck.cc
> > +++ b/gcc/cp/typeck.cc
> > @@ -10837,37 +10837,37 @@ treat_lvalue_as_rvalue_p (tree expr, bool return_p)
> >        parenthesized) id-expression that names an implicitly movable entity
> >        declared in the body or parameter-declaration-clause of the innermost
> >        enclosing function or lambda-expression, */
> > -  if (DECL_CONTEXT (retval) != current_function_decl)
> > -    return NULL_TREE;
> >     if (return_p)
> >       {
> > +      if (DECL_CONTEXT (retval) != current_function_decl)
> > +	return NULL_TREE;
> >         expr = move (expr);
> >         if (expr == error_mark_node)
> >   	return NULL_TREE;
> >         return set_implicit_rvalue_p (expr);
> >       }
> > -  /* if the operand of a throw-expression is a (possibly parenthesized)
> > -     id-expression that names an implicitly movable entity whose scope does not
> > -     extend beyond the compound-statement of the innermost try-block or
> > -     function-try-block (if any) whose compound-statement or ctor-initializer
> > -     encloses the throw-expression, */
> > +  /* if the id-expression (possibly parenthesized) is the operand of
> > +     a throw-expression, and names an implicitly movable entity that belongs
> > +     to a scope that does not contain the compound-statement of the innermost
> > +     lambda-expression, try-block, or function-try-block (if any) whose
> > +     compound-statement or ctor-initializer contains the throw-expression.  */
> 
> Please also mention here why you aren't checking for lambdas.

Done.

> >     /* C++20 added move on throw of parms.  */
> >     if (TREE_CODE (retval) == PARM_DECL && cxx_dialect < cxx20)
> >       return NULL_TREE;
> >     for (cp_binding_level *b = current_binding_level;
> > -       ; b = b->level_chain)
> > -    {
> > -      for (tree decl = b->names; decl; decl = TREE_CHAIN (decl))
> > -	if (decl == retval)
> > -	  return set_implicit_rvalue_p (move (expr));
> > -      if (b->kind == sk_function_parms
> > -	  || b->kind == sk_try
> > -	  || b->kind == sk_namespace)
> > +       b->kind != sk_namespace; b = b->level_chain)
> > +    if (b->kind == sk_try)
> > +      {
> > +	for (tree decl = b->names; decl; decl = TREE_CHAIN (decl))
> > +	  if (decl == retval)
> > +	    return set_implicit_rvalue_p (move (expr));
> >   	return NULL_TREE;
> > -    }
> 
> What if the variable is in a block nested within the try-block?  I think we
> still want to walk b->names for every inner binding level.

Oy, that's a bug.  Fixed by moving the == sk_try check below.

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

-- >8 --
Here we have

  template<class T>
  auto is_throwable(T t) -> decltype(throw t, true) { ... }

where we didn't properly mark 't' as IMPLICIT_RVALUE_P, which caused
the wrong overload to have been chosen.  Jason figured out it's because
we don't correctly implement [expr.prim.id.unqual]#4.2, which post-P2266
says that an id-expression is move-eligible if

"the id-expression (possibly parenthesized) is the operand of
a throw-expression, and names an implicitly movable entity that belongs
to a scope that does not contain the compound-statement of the innermost
lambda-expression, try-block, or function-try-block (if any) whose
compound-statement or ctor-initializer contains the throw-expression."

I worked out that it's trying to say that given

  struct X {
    X();
    X(const X&);
    X(X&&) = delete;
  };

the following should fail: the scope of the throw is an sk_try, and it's
also x's scope S, and S "does not contain the compound-statement of the
*try-block" so x is move-eligible, so we move, so we fail.

  void f ()
  try {
    X x;
    throw x;  // use of deleted function
  } catch (...) {
  }

Whereas here:

  void g (X x)
  try {
    throw x;
  } catch (...) {
  }

the throw is again in an sk_try, but x's scope is an sk_function_parms
which *does* contain the {} of the *try-block, so x is not move-eligible,
so we don't move, so we use X(const X&), and the code is fine.

The current code also doesn't seem to handle

  void h (X x) {
    void z (decltype(throw x, true));
  }

where there's no enclosing lambda or sk_try so we should move.

I'm not doing anything about lambdas because we shouldn't reach the
code at the end of the function: the DECL_HAS_VALUE_EXPR_P check
shouldn't let us go further.

	PR c++/113789
	PR c++/113853

gcc/cp/ChangeLog:

	* typeck.cc (treat_lvalue_as_rvalue_p): Update code to better
	reflect [expr.prim.id.unqual]#4.2.

gcc/testsuite/ChangeLog:

	* g++.dg/cpp0x/sfinae69.C: Remove dg-bogus.
	* g++.dg/cpp0x/sfinae70.C: New test.
	* g++.dg/cpp0x/sfinae71.C: New test.
	* g++.dg/cpp0x/sfinae72.C: New test.
	* g++.dg/cpp2a/implicit-move4.C: New test.
---
 gcc/cp/typeck.cc                            | 24 +++---
 gcc/testsuite/g++.dg/cpp0x/sfinae69.C       |  2 +-
 gcc/testsuite/g++.dg/cpp0x/sfinae70.C       | 16 ++++
 gcc/testsuite/g++.dg/cpp0x/sfinae71.C       | 17 ++++
 gcc/testsuite/g++.dg/cpp0x/sfinae72.C       | 17 ++++
 gcc/testsuite/g++.dg/cpp2a/implicit-move4.C | 88 +++++++++++++++++++++
 6 files changed, 152 insertions(+), 12 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae70.C
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae71.C
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae72.C
 create mode 100644 gcc/testsuite/g++.dg/cpp2a/implicit-move4.C

diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
index 132c55cfc6d..f5a0a2273be 100644
--- a/gcc/cp/typeck.cc
+++ b/gcc/cp/typeck.cc
@@ -10837,37 +10837,39 @@ treat_lvalue_as_rvalue_p (tree expr, bool return_p)
      parenthesized) id-expression that names an implicitly movable entity
      declared in the body or parameter-declaration-clause of the innermost
      enclosing function or lambda-expression, */
-  if (DECL_CONTEXT (retval) != current_function_decl)
-    return NULL_TREE;
   if (return_p)
     {
+      if (DECL_CONTEXT (retval) != current_function_decl)
+	return NULL_TREE;
       expr = move (expr);
       if (expr == error_mark_node)
 	return NULL_TREE;
       return set_implicit_rvalue_p (expr);
     }
 
-  /* if the operand of a throw-expression is a (possibly parenthesized)
-     id-expression that names an implicitly movable entity whose scope does not
-     extend beyond the compound-statement of the innermost try-block or
-     function-try-block (if any) whose compound-statement or ctor-initializer
-     encloses the throw-expression, */
+  /* if the id-expression (possibly parenthesized) is the operand of
+     a throw-expression, and names an implicitly movable entity that belongs
+     to a scope that does not contain the compound-statement of the innermost
+     lambda-expression, try-block, or function-try-block (if any) whose
+     compound-statement or ctor-initializer contains the throw-expression.  */
 
   /* C++20 added move on throw of parms.  */
   if (TREE_CODE (retval) == PARM_DECL && cxx_dialect < cxx20)
     return NULL_TREE;
 
+  /* We don't check for lambda-expression here, because we should not get past
+     the DECL_HAS_VALUE_EXPR_P check above.  */
   for (cp_binding_level *b = current_binding_level;
-       ; b = b->level_chain)
+       b->kind != sk_namespace; b = b->level_chain)
     {
       for (tree decl = b->names; decl; decl = TREE_CHAIN (decl))
 	if (decl == retval)
 	  return set_implicit_rvalue_p (move (expr));
-      if (b->kind == sk_function_parms
-	  || b->kind == sk_try
-	  || b->kind == sk_namespace)
+      if (b->kind == sk_try)
 	return NULL_TREE;
     }
+
+  return set_implicit_rvalue_p (move (expr));
 }
 
 /* Warn about dubious usage of std::move (in a return statement, if RETURN_P
diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae69.C b/gcc/testsuite/g++.dg/cpp0x/sfinae69.C
index 361e0b79ba2..60eba61165d 100644
--- a/gcc/testsuite/g++.dg/cpp0x/sfinae69.C
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae69.C
@@ -15,7 +15,7 @@ constexpr bool is_throwable(...) { return false; }
 
 constexpr bool b = is_throwable<moveonly>(moveonly{});
 #if __cplusplus >= 202002L
-static_assert (b, "move from the function parameter"); // { dg-bogus "" "PR113853" { xfail c++20 } }
+static_assert (b, "move from the function parameter");
 #else
 static_assert (!b, "no move from the function parameter");
 #endif
diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae70.C b/gcc/testsuite/g++.dg/cpp0x/sfinae70.C
new file mode 100644
index 00000000000..48ea70a61a4
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae70.C
@@ -0,0 +1,16 @@
+// PR c++/113789
+// { dg-do compile { target c++11 } }
+
+struct AutoPtr {
+    AutoPtr() = default;
+    AutoPtr(AutoPtr&) {}
+};
+
+template<class T> auto f(T p, int) -> decltype(throw p, 1) = delete;
+template<class T> void f(T p, long);
+
+void
+g ()
+{
+  f (AutoPtr (), 42); // { dg-error "use of deleted function" "" { target c++20_down } }
+}
diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae71.C b/gcc/testsuite/g++.dg/cpp0x/sfinae71.C
new file mode 100644
index 00000000000..2fefe5f70e0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae71.C
@@ -0,0 +1,17 @@
+// PR c++/113789
+// { dg-do compile { target c++11 } }
+// Like sfinae70.C but T&&.
+
+struct AutoPtr {
+    AutoPtr() = default;
+    AutoPtr(AutoPtr&) {}
+};
+
+template<class T> auto f(T&& p, int) -> decltype(throw p, 1) = delete;
+template<class T> void f(T p, long);
+
+void
+g ()
+{
+  f (AutoPtr (), 42); // { dg-error "use of deleted function" "" { target c++20_down } }
+}
diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae72.C b/gcc/testsuite/g++.dg/cpp0x/sfinae72.C
new file mode 100644
index 00000000000..397cdbd8c23
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/sfinae72.C
@@ -0,0 +1,17 @@
+// PR c++/113789
+// { dg-do compile { target c++11 } }
+// Like sfinae70.C but ().
+
+struct AutoPtr {
+    AutoPtr() = default;
+    AutoPtr(AutoPtr&) {}
+};
+
+template<class T> auto f(T p, int) -> decltype(throw (p), 1) = delete;
+template<class T> void f(T p, long);
+
+void
+g ()
+{
+  f (AutoPtr (), 42); // { dg-error "use of deleted function" "" { target c++20_down } }
+}
diff --git a/gcc/testsuite/g++.dg/cpp2a/implicit-move4.C b/gcc/testsuite/g++.dg/cpp2a/implicit-move4.C
new file mode 100644
index 00000000000..09ac5c93ab9
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/implicit-move4.C
@@ -0,0 +1,88 @@
+// PR c++/113853
+// { dg-do compile { target c++20 } }
+
+struct X {
+  X();
+  X(const X&);
+  X(X&&) = delete;
+};
+
+void
+f1 ()
+{
+  try {
+    ;
+  } catch (X x) {
+    throw x; // { dg-error "use of deleted function" }
+  }
+}
+
+void
+f2 (X x)
+try {
+  ;
+} catch (...) {
+  throw x;  // { dg-error "use of deleted function" }
+}
+
+void
+f2b (X x)
+try {
+  ;
+} catch (...) {
+  {
+    throw x;  // { dg-error "use of deleted function" }
+  }
+}
+
+void
+f3 ()
+try {
+  X x;
+  throw x;  // { dg-error "use of deleted function" }
+} catch (...) {
+}
+
+void
+f3b ()
+try {
+  {
+    X x;
+    throw x;  // { dg-error "use of deleted function" }
+  }
+} catch (...) {
+}
+
+void
+f4 (X x)
+try {
+  throw x;
+} catch (...) {
+}
+
+void
+f4b (X x)
+try {
+  {
+    throw x;
+  }
+} catch (...) {
+}
+
+void
+f5 (X x)
+{
+  void g (decltype(throw x, true));	// { dg-error "use of deleted function|expected" }
+}
+
+// The "expected" shouldn't be here, c++/113924.
+void
+f6 (X x, int = decltype(throw x, true){}) // { dg-error "use of deleted function|expected" }
+{
+}
+
+void
+f7 (X x)
+{
+  [&] { throw x; };
+}

base-commit: 7c6071a66f32f43cea7aa4aa32d89b338e768307
-- 
2.43.2

Re: [PATCH v2] c++: implicit move with throw [PR113853]

[Jason Merrill]

On 2/16/24 10:58, Marek Polacek wrote:
> On Thu, Feb 15, 2024 at 04:36:40PM -0500, Jason Merrill wrote:
>> On 2/15/24 10:19, Marek Polacek wrote:
>>> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?
>>>
>>> -- >8 --
>>> Here we have
>>>
>>>     template<class T>
>>>     auto is_throwable(T t) -> decltype(throw t, true) { ... }
>>>
>>> where we didn't properly mark 't' as IMPLICIT_RVALUE_P, which caused
>>> the wrong overload to have been chosen.  Jason figured out it's because
>>> we don't correctly implement [expr.prim.id.unqual]#4.2, which post-P2266
>>> says that an id-expression is move-eligible if
>>>
>>> "the id-expression (possibly parenthesized) is the operand of
>>> a throw-expression, and names an implicitly movable entity that belongs
>>> to a scope that does not contain the compound-statement of the innermost
>>> lambda-expression, try-block, or function-try-block (if any) whose
>>> compound-statement or ctor-initializer contains the throw-expression."
>>>
>>> I worked out that it's trying to say that given
>>>
>>>     struct X {
>>>       X();
>>>       X(const X&);
>>>       X(X&&) = delete;
>>>     };
>>>
>>> the following should fail: the scope of the throw is an sk_try, and it's
>>> also x's scope S, and S "does not contain the compound-statement of the
>>> *try-block" so x is move-eligible, so we move, so we fail.
>>>
>>>     void f ()
>>>     try {
>>>       X x;
>>>       throw x;  // use of deleted function
>>>     } catch (...) {
>>>     }
>>>
>>> Whereas here:
>>>
>>>     void g (X x)
>>>     try {
>>>       throw x;
>>>     } catch (...) {
>>>     }
>>>
>>> the throw is again in an sk_try, but x's scope is an sk_function_parms
>>> which *does* contain the {} of the *try-block, so x is not move-eligible,
>>> so we don't move, so we use X(const X&), and the code is fine.
>>>
>>> The current code also doesn't seem to handle
>>>
>>>     void h (X x) {
>>>       void z (decltype(throw x, true));
>>>     }
>>>
>>> where there's no enclosing lambda or sk_try so we should move.
>>>
>>> I'm not doing anything about lambdas because we shouldn't reach the
>>> code at the end of the function: the DECL_HAS_VALUE_EXPR_P check
>>> shouldn't let us go further.
>>>
>>> 	PR c++/113789
>>> 	PR c++/113853
>>>
>>> gcc/cp/ChangeLog:
>>>
>>> 	* typeck.cc (treat_lvalue_as_rvalue_p): Update code to better
>>> 	reflect [expr.prim.id.unqual]#4.2.
>>>
>>> gcc/testsuite/ChangeLog:
>>>
>>> 	* g++.dg/cpp0x/sfinae69.C: Remove dg-bogus.
>>> 	* g++.dg/cpp0x/sfinae70.C: New test.
>>> 	* g++.dg/cpp0x/sfinae71.C: New test.
>>> 	* g++.dg/cpp0x/sfinae72.C: New test.
>>> 	* g++.dg/cpp2a/implicit-move4.C: New test.
>>> ---
>>>    gcc/cp/typeck.cc                            | 32 +++++------
>>>    gcc/testsuite/g++.dg/cpp0x/sfinae69.C       |  2 +-
>>>    gcc/testsuite/g++.dg/cpp0x/sfinae70.C       | 16 ++++++
>>>    gcc/testsuite/g++.dg/cpp0x/sfinae71.C       | 17 ++++++
>>>    gcc/testsuite/g++.dg/cpp0x/sfinae72.C       | 17 ++++++
>>>    gcc/testsuite/g++.dg/cpp2a/implicit-move4.C | 59 +++++++++++++++++++++
>>>    6 files changed, 126 insertions(+), 17 deletions(-)
>>>    create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae70.C
>>>    create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae71.C
>>>    create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae72.C
>>>    create mode 100644 gcc/testsuite/g++.dg/cpp2a/implicit-move4.C
>>>
>>> diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
>>> index 132c55cfc6d..0dc44cd87ca 100644
>>> --- a/gcc/cp/typeck.cc
>>> +++ b/gcc/cp/typeck.cc
>>> @@ -10837,37 +10837,37 @@ treat_lvalue_as_rvalue_p (tree expr, bool return_p)
>>>         parenthesized) id-expression that names an implicitly movable entity
>>>         declared in the body or parameter-declaration-clause of the innermost
>>>         enclosing function or lambda-expression, */
>>> -  if (DECL_CONTEXT (retval) != current_function_decl)
>>> -    return NULL_TREE;
>>>      if (return_p)
>>>        {
>>> +      if (DECL_CONTEXT (retval) != current_function_decl)
>>> +	return NULL_TREE;
>>>          expr = move (expr);
>>>          if (expr == error_mark_node)
>>>    	return NULL_TREE;
>>>          return set_implicit_rvalue_p (expr);
>>>        }
>>> -  /* if the operand of a throw-expression is a (possibly parenthesized)
>>> -     id-expression that names an implicitly movable entity whose scope does not
>>> -     extend beyond the compound-statement of the innermost try-block or
>>> -     function-try-block (if any) whose compound-statement or ctor-initializer
>>> -     encloses the throw-expression, */
>>> +  /* if the id-expression (possibly parenthesized) is the operand of
>>> +     a throw-expression, and names an implicitly movable entity that belongs
>>> +     to a scope that does not contain the compound-statement of the innermost
>>> +     lambda-expression, try-block, or function-try-block (if any) whose
>>> +     compound-statement or ctor-initializer contains the throw-expression.  */
>>
>> Please also mention here why you aren't checking for lambdas.
> 
> Done.
> 
>>>      /* C++20 added move on throw of parms.  */
>>>      if (TREE_CODE (retval) == PARM_DECL && cxx_dialect < cxx20)
>>>        return NULL_TREE;
>>>      for (cp_binding_level *b = current_binding_level;
>>> -       ; b = b->level_chain)
>>> -    {
>>> -      for (tree decl = b->names; decl; decl = TREE_CHAIN (decl))
>>> -	if (decl == retval)
>>> -	  return set_implicit_rvalue_p (move (expr));
>>> -      if (b->kind == sk_function_parms
>>> -	  || b->kind == sk_try
>>> -	  || b->kind == sk_namespace)
>>> +       b->kind != sk_namespace; b = b->level_chain)
>>> +    if (b->kind == sk_try)
>>> +      {
>>> +	for (tree decl = b->names; decl; decl = TREE_CHAIN (decl))
>>> +	  if (decl == retval)
>>> +	    return set_implicit_rvalue_p (move (expr));
>>>    	return NULL_TREE;
>>> -    }
>>
>> What if the variable is in a block nested within the try-block?  I think we
>> still want to walk b->names for every inner binding level.
> 
> Oy, that's a bug.  Fixed by moving the == sk_try check below.
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK.

> -- >8 --
> Here we have
> 
>    template<class T>
>    auto is_throwable(T t) -> decltype(throw t, true) { ... }
> 
> where we didn't properly mark 't' as IMPLICIT_RVALUE_P, which caused
> the wrong overload to have been chosen.  Jason figured out it's because
> we don't correctly implement [expr.prim.id.unqual]#4.2, which post-P2266
> says that an id-expression is move-eligible if
> 
> "the id-expression (possibly parenthesized) is the operand of
> a throw-expression, and names an implicitly movable entity that belongs
> to a scope that does not contain the compound-statement of the innermost
> lambda-expression, try-block, or function-try-block (if any) whose
> compound-statement or ctor-initializer contains the throw-expression."
> 
> I worked out that it's trying to say that given
> 
>    struct X {
>      X();
>      X(const X&);
>      X(X&&) = delete;
>    };
> 
> the following should fail: the scope of the throw is an sk_try, and it's
> also x's scope S, and S "does not contain the compound-statement of the
> *try-block" so x is move-eligible, so we move, so we fail.
> 
>    void f ()
>    try {
>      X x;
>      throw x;  // use of deleted function
>    } catch (...) {
>    }
> 
> Whereas here:
> 
>    void g (X x)
>    try {
>      throw x;
>    } catch (...) {
>    }
> 
> the throw is again in an sk_try, but x's scope is an sk_function_parms
> which *does* contain the {} of the *try-block, so x is not move-eligible,
> so we don't move, so we use X(const X&), and the code is fine.
> 
> The current code also doesn't seem to handle
> 
>    void h (X x) {
>      void z (decltype(throw x, true));
>    }
> 
> where there's no enclosing lambda or sk_try so we should move.
> 
> I'm not doing anything about lambdas because we shouldn't reach the
> code at the end of the function: the DECL_HAS_VALUE_EXPR_P check
> shouldn't let us go further.
> 
> 	PR c++/113789
> 	PR c++/113853
> 
> gcc/cp/ChangeLog:
> 
> 	* typeck.cc (treat_lvalue_as_rvalue_p): Update code to better
> 	reflect [expr.prim.id.unqual]#4.2.
> 
> gcc/testsuite/ChangeLog:
> 
> 	* g++.dg/cpp0x/sfinae69.C: Remove dg-bogus.
> 	* g++.dg/cpp0x/sfinae70.C: New test.
> 	* g++.dg/cpp0x/sfinae71.C: New test.
> 	* g++.dg/cpp0x/sfinae72.C: New test.
> 	* g++.dg/cpp2a/implicit-move4.C: New test.
> ---
>   gcc/cp/typeck.cc                            | 24 +++---
>   gcc/testsuite/g++.dg/cpp0x/sfinae69.C       |  2 +-
>   gcc/testsuite/g++.dg/cpp0x/sfinae70.C       | 16 ++++
>   gcc/testsuite/g++.dg/cpp0x/sfinae71.C       | 17 ++++
>   gcc/testsuite/g++.dg/cpp0x/sfinae72.C       | 17 ++++
>   gcc/testsuite/g++.dg/cpp2a/implicit-move4.C | 88 +++++++++++++++++++++
>   6 files changed, 152 insertions(+), 12 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae70.C
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae71.C
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/sfinae72.C
>   create mode 100644 gcc/testsuite/g++.dg/cpp2a/implicit-move4.C
> 
> diff --git a/gcc/cp/typeck.cc b/gcc/cp/typeck.cc
> index 132c55cfc6d..f5a0a2273be 100644
> --- a/gcc/cp/typeck.cc
> +++ b/gcc/cp/typeck.cc
> @@ -10837,37 +10837,39 @@ treat_lvalue_as_rvalue_p (tree expr, bool return_p)
>        parenthesized) id-expression that names an implicitly movable entity
>        declared in the body or parameter-declaration-clause of the innermost
>        enclosing function or lambda-expression, */
> -  if (DECL_CONTEXT (retval) != current_function_decl)
> -    return NULL_TREE;
>     if (return_p)
>       {
> +      if (DECL_CONTEXT (retval) != current_function_decl)
> +	return NULL_TREE;
>         expr = move (expr);
>         if (expr == error_mark_node)
>   	return NULL_TREE;
>         return set_implicit_rvalue_p (expr);
>       }
>   
> -  /* if the operand of a throw-expression is a (possibly parenthesized)
> -     id-expression that names an implicitly movable entity whose scope does not
> -     extend beyond the compound-statement of the innermost try-block or
> -     function-try-block (if any) whose compound-statement or ctor-initializer
> -     encloses the throw-expression, */
> +  /* if the id-expression (possibly parenthesized) is the operand of
> +     a throw-expression, and names an implicitly movable entity that belongs
> +     to a scope that does not contain the compound-statement of the innermost
> +     lambda-expression, try-block, or function-try-block (if any) whose
> +     compound-statement or ctor-initializer contains the throw-expression.  */
>   
>     /* C++20 added move on throw of parms.  */
>     if (TREE_CODE (retval) == PARM_DECL && cxx_dialect < cxx20)
>       return NULL_TREE;
>   
> +  /* We don't check for lambda-expression here, because we should not get past
> +     the DECL_HAS_VALUE_EXPR_P check above.  */
>     for (cp_binding_level *b = current_binding_level;
> -       ; b = b->level_chain)
> +       b->kind != sk_namespace; b = b->level_chain)
>       {
>         for (tree decl = b->names; decl; decl = TREE_CHAIN (decl))
>   	if (decl == retval)
>   	  return set_implicit_rvalue_p (move (expr));
> -      if (b->kind == sk_function_parms
> -	  || b->kind == sk_try
> -	  || b->kind == sk_namespace)
> +      if (b->kind == sk_try)
>   	return NULL_TREE;
>       }
> +
> +  return set_implicit_rvalue_p (move (expr));
>   }
>   
>   /* Warn about dubious usage of std::move (in a return statement, if RETURN_P
> diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae69.C b/gcc/testsuite/g++.dg/cpp0x/sfinae69.C
> index 361e0b79ba2..60eba61165d 100644
> --- a/gcc/testsuite/g++.dg/cpp0x/sfinae69.C
> +++ b/gcc/testsuite/g++.dg/cpp0x/sfinae69.C
> @@ -15,7 +15,7 @@ constexpr bool is_throwable(...) { return false; }
>   
>   constexpr bool b = is_throwable<moveonly>(moveonly{});
>   #if __cplusplus >= 202002L
> -static_assert (b, "move from the function parameter"); // { dg-bogus "" "PR113853" { xfail c++20 } }
> +static_assert (b, "move from the function parameter");
>   #else
>   static_assert (!b, "no move from the function parameter");
>   #endif
> diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae70.C b/gcc/testsuite/g++.dg/cpp0x/sfinae70.C
> new file mode 100644
> index 00000000000..48ea70a61a4
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/sfinae70.C
> @@ -0,0 +1,16 @@
> +// PR c++/113789
> +// { dg-do compile { target c++11 } }
> +
> +struct AutoPtr {
> +    AutoPtr() = default;
> +    AutoPtr(AutoPtr&) {}
> +};
> +
> +template<class T> auto f(T p, int) -> decltype(throw p, 1) = delete;
> +template<class T> void f(T p, long);
> +
> +void
> +g ()
> +{
> +  f (AutoPtr (), 42); // { dg-error "use of deleted function" "" { target c++20_down } }
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae71.C b/gcc/testsuite/g++.dg/cpp0x/sfinae71.C
> new file mode 100644
> index 00000000000..2fefe5f70e0
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/sfinae71.C
> @@ -0,0 +1,17 @@
> +// PR c++/113789
> +// { dg-do compile { target c++11 } }
> +// Like sfinae70.C but T&&.
> +
> +struct AutoPtr {
> +    AutoPtr() = default;
> +    AutoPtr(AutoPtr&) {}
> +};
> +
> +template<class T> auto f(T&& p, int) -> decltype(throw p, 1) = delete;
> +template<class T> void f(T p, long);
> +
> +void
> +g ()
> +{
> +  f (AutoPtr (), 42); // { dg-error "use of deleted function" "" { target c++20_down } }
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp0x/sfinae72.C b/gcc/testsuite/g++.dg/cpp0x/sfinae72.C
> new file mode 100644
> index 00000000000..397cdbd8c23
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/sfinae72.C
> @@ -0,0 +1,17 @@
> +// PR c++/113789
> +// { dg-do compile { target c++11 } }
> +// Like sfinae70.C but ().
> +
> +struct AutoPtr {
> +    AutoPtr() = default;
> +    AutoPtr(AutoPtr&) {}
> +};
> +
> +template<class T> auto f(T p, int) -> decltype(throw (p), 1) = delete;
> +template<class T> void f(T p, long);
> +
> +void
> +g ()
> +{
> +  f (AutoPtr (), 42); // { dg-error "use of deleted function" "" { target c++20_down } }
> +}
> diff --git a/gcc/testsuite/g++.dg/cpp2a/implicit-move4.C b/gcc/testsuite/g++.dg/cpp2a/implicit-move4.C
> new file mode 100644
> index 00000000000..09ac5c93ab9
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp2a/implicit-move4.C
> @@ -0,0 +1,88 @@
> +// PR c++/113853
> +// { dg-do compile { target c++20 } }
> +
> +struct X {
> +  X();
> +  X(const X&);
> +  X(X&&) = delete;
> +};
> +
> +void
> +f1 ()
> +{
> +  try {
> +    ;
> +  } catch (X x) {
> +    throw x; // { dg-error "use of deleted function" }
> +  }
> +}
> +
> +void
> +f2 (X x)
> +try {
> +  ;
> +} catch (...) {
> +  throw x;  // { dg-error "use of deleted function" }
> +}
> +
> +void
> +f2b (X x)
> +try {
> +  ;
> +} catch (...) {
> +  {
> +    throw x;  // { dg-error "use of deleted function" }
> +  }
> +}
> +
> +void
> +f3 ()
> +try {
> +  X x;
> +  throw x;  // { dg-error "use of deleted function" }
> +} catch (...) {
> +}
> +
> +void
> +f3b ()
> +try {
> +  {
> +    X x;
> +    throw x;  // { dg-error "use of deleted function" }
> +  }
> +} catch (...) {
> +}
> +
> +void
> +f4 (X x)
> +try {
> +  throw x;
> +} catch (...) {
> +}
> +
> +void
> +f4b (X x)
> +try {
> +  {
> +    throw x;
> +  }
> +} catch (...) {
> +}
> +
> +void
> +f5 (X x)
> +{
> +  void g (decltype(throw x, true));	// { dg-error "use of deleted function|expected" }
> +}
> +
> +// The "expected" shouldn't be here, c++/113924.
> +void
> +f6 (X x, int = decltype(throw x, true){}) // { dg-error "use of deleted function|expected" }
> +{
> +}
> +
> +void
> +f7 (X x)
> +{
> +  [&] { throw x; };
> +}
> 
> base-commit: 7c6071a66f32f43cea7aa4aa32d89b338e768307