[PATCH] c++: Fix thinko in auto return type checking [PR98441]

[PATCH] c++: Fix thinko in auto return type checking [PR98441]

[Marek Polacek]

This fixes a thinko in my r11-2085 patch: when I said "But only give the
!late_return_type errors when funcdecl_p, to accept e.g. auto (*fp)() = f;
in C++11" I should've done this, otherwise we give bogus errors mentioning
"function with trailing return type" when there is none.

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

gcc/cp/ChangeLog:

	PR c++/98441
	* decl.c (grokdeclarator): Move the !funcdecl_p check inside the
	!late_return_type block.

gcc/testsuite/ChangeLog:

	PR c++/98441
	* g++.dg/cpp0x/auto55.C: New test.
---
 gcc/cp/decl.c                       |  8 +++++---
 gcc/testsuite/g++.dg/cpp0x/auto55.C | 13 +++++++++++++
 2 files changed, 18 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/auto55.C

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index bf6f12c26a0..1a114a2e2d0 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -12241,10 +12241,12 @@ grokdeclarator (const cp_declarator *declarator,
 	    tree late_return_type = declarator->u.function.late_return_type;
 	    if (tree auto_node = type_uses_auto (type))
 	      {
-		if (!late_return_type && funcdecl_p)
+		if (!late_return_type)
 		  {
-		    if (current_class_type
-			&& LAMBDA_TYPE_P (current_class_type))
+		    if (!funcdecl_p)
+		      /* auto (*fp)() = f; is OK.  */;
+		    else if (current_class_type
+			     && LAMBDA_TYPE_P (current_class_type))
 		      /* OK for C++11 lambdas.  */;
 		    else if (cxx_dialect < cxx14)
 		      {
diff --git a/gcc/testsuite/g++.dg/cpp0x/auto55.C b/gcc/testsuite/g++.dg/cpp0x/auto55.C
new file mode 100644
index 00000000000..5bd32ac890d
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/auto55.C
@@ -0,0 +1,13 @@
+// PR c++/98441
+// { dg-do compile { target c++11 } }
+
+struct a {
+    int& mfn();
+};
+
+void fn()
+{
+    int&  (a::*myvar1)(void) = &a::mfn;
+    auto& (a::*myvar2)(void) = &a::mfn;
+    auto  (a::*myvar3)(void) = &a::mfn;
+}

base-commit: ad92bf4b165935b58195825dc8f089f53fd2710b
-- 
2.29.2

Re: [PATCH] c++: Fix thinko in auto return type checking [PR98441]

[Jason Merrill]

On 1/5/21 7:31 PM, Marek Polacek wrote:
> This fixes a thinko in my r11-2085 patch: when I said "But only give the
> !late_return_type errors when funcdecl_p, to accept e.g. auto (*fp)() = f;
> in C++11" I should've done this, otherwise we give bogus errors mentioning
> "function with trailing return type" when there is none.
> 
> Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

OK.

> gcc/cp/ChangeLog:
> 
> 	PR c++/98441
> 	* decl.c (grokdeclarator): Move the !funcdecl_p check inside the
> 	!late_return_type block.
> 
> gcc/testsuite/ChangeLog:
> 
> 	PR c++/98441
> 	* g++.dg/cpp0x/auto55.C: New test.
> ---
>   gcc/cp/decl.c                       |  8 +++++---
>   gcc/testsuite/g++.dg/cpp0x/auto55.C | 13 +++++++++++++
>   2 files changed, 18 insertions(+), 3 deletions(-)
>   create mode 100644 gcc/testsuite/g++.dg/cpp0x/auto55.C
> 
> diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
> index bf6f12c26a0..1a114a2e2d0 100644
> --- a/gcc/cp/decl.c
> +++ b/gcc/cp/decl.c
> @@ -12241,10 +12241,12 @@ grokdeclarator (const cp_declarator *declarator,
>   	    tree late_return_type = declarator->u.function.late_return_type;
>   	    if (tree auto_node = type_uses_auto (type))
>   	      {
> -		if (!late_return_type && funcdecl_p)
> +		if (!late_return_type)
>   		  {
> -		    if (current_class_type
> -			&& LAMBDA_TYPE_P (current_class_type))
> +		    if (!funcdecl_p)
> +		      /* auto (*fp)() = f; is OK.  */;
> +		    else if (current_class_type
> +			     && LAMBDA_TYPE_P (current_class_type))
>   		      /* OK for C++11 lambdas.  */;
>   		    else if (cxx_dialect < cxx14)
>   		      {
> diff --git a/gcc/testsuite/g++.dg/cpp0x/auto55.C b/gcc/testsuite/g++.dg/cpp0x/auto55.C
> new file mode 100644
> index 00000000000..5bd32ac890d
> --- /dev/null
> +++ b/gcc/testsuite/g++.dg/cpp0x/auto55.C
> @@ -0,0 +1,13 @@
> +// PR c++/98441
> +// { dg-do compile { target c++11 } }
> +
> +struct a {
> +    int& mfn();
> +};
> +
> +void fn()
> +{
> +    int&  (a::*myvar1)(void) = &a::mfn;
> +    auto& (a::*myvar2)(void) = &a::mfn;
> +    auto  (a::*myvar3)(void) = &a::mfn;
> +}
> 
> base-commit: ad92bf4b165935b58195825dc8f089f53fd2710b
>