c++: abbreviated function template friend matching [PR96106]

Message ID 20200720201831.3759722-1-ppalka@redhat.com
State New
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Series
  • c++: abbreviated function template friend matching [PR96106]
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Commit Message

Ian Lance Taylor via Gcc-patches July 20, 2020, 8:18 p.m.
In the below testcase, duplicate_decls wasn't merging the tsubsted
friend declaration for 'void add(auto)' with its definition, because
reduce_template_parm_level (during tsubst_friend_function) lost the
DECL_VIRTUAL_P flag on the invented 'auto' template parameter, which
made template_heads_equivalent_p deem the two template heads as not
equivalent in C++20 mode.

This patch makes reduce_template_parm_level carry over the
DECL_VIRTUAL_P from the original TEMPLATE_PARM_DECL.

Passes 'make check-c++' and the cmcstl2 testsuite.  Does this look OK
for trunk after a full bootstrap and regtest?

gcc/cp/ChangeLog:

	PR c++/96106
	* pt.c (reduce_template_parm_level): Carry over DECL_VIRTUAL_P
	from the original TEMPLATE_PARM_DECL.

gcc/testsuite/ChangeLog:

	PR c++/96106
	* g++.dg/concepts/abbrev7.C: New test.
---
 gcc/cp/pt.c                             |  1 +
 gcc/testsuite/g++.dg/concepts/abbrev7.C | 14 ++++++++++++++
 2 files changed, 15 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/concepts/abbrev7.C

-- 
2.28.0.rc1

Comments

Ian Lance Taylor via Gcc-patches July 29, 2020, 9:57 p.m. | #1
On 7/20/20 4:18 PM, Patrick Palka wrote:
> In the below testcase, duplicate_decls wasn't merging the tsubsted

> friend declaration for 'void add(auto)' with its definition, because

> reduce_template_parm_level (during tsubst_friend_function) lost the

> DECL_VIRTUAL_P flag on the invented 'auto' template parameter, which

> made template_heads_equivalent_p deem the two template heads as not

> equivalent in C++20 mode.

> 

> This patch makes reduce_template_parm_level carry over the

> DECL_VIRTUAL_P from the original TEMPLATE_PARM_DECL.

> 

> Passes 'make check-c++' and the cmcstl2 testsuite.  Does this look OK

> for trunk after a full bootstrap and regtest?


OK.

> gcc/cp/ChangeLog:

> 

> 	PR c++/96106

> 	* pt.c (reduce_template_parm_level): Carry over DECL_VIRTUAL_P

> 	from the original TEMPLATE_PARM_DECL.

> 

> gcc/testsuite/ChangeLog:

> 

> 	PR c++/96106

> 	* g++.dg/concepts/abbrev7.C: New test.

> ---

>   gcc/cp/pt.c                             |  1 +

>   gcc/testsuite/g++.dg/concepts/abbrev7.C | 14 ++++++++++++++

>   2 files changed, 15 insertions(+)

>   create mode 100644 gcc/testsuite/g++.dg/concepts/abbrev7.C

> 

> diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c

> index defc2a9abd8..3f7b89141b6 100644

> --- a/gcc/cp/pt.c

> +++ b/gcc/cp/pt.c

> @@ -4453,6 +4453,7 @@ reduce_template_parm_level (tree index, tree type, int levels, tree args,

>   			      type);

>         TREE_CONSTANT (decl) = TREE_CONSTANT (orig_decl);

>         TREE_READONLY (decl) = TREE_READONLY (orig_decl);

> +      DECL_VIRTUAL_P (decl) = DECL_VIRTUAL_P (orig_decl);

>         DECL_ARTIFICIAL (decl) = 1;

>         SET_DECL_TEMPLATE_PARM_P (decl);

>   

> diff --git a/gcc/testsuite/g++.dg/concepts/abbrev7.C b/gcc/testsuite/g++.dg/concepts/abbrev7.C

> new file mode 100644

> index 00000000000..443c1b7871b

> --- /dev/null

> +++ b/gcc/testsuite/g++.dg/concepts/abbrev7.C

> @@ -0,0 +1,14 @@

> +// PR c++/96106

> +// { dg-do compile { target concepts } }

> +

> +template<typename>

> +struct number {

> +  friend void add(auto);

> +};

> +

> +void add(auto) { }

> +

> +void foo() {

> +  number<int> n;

> +  add(n); // { dg-bogus "ambiguous" }

> +}

>

Patch

diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index defc2a9abd8..3f7b89141b6 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -4453,6 +4453,7 @@  reduce_template_parm_level (tree index, tree type, int levels, tree args,
 			      type);
       TREE_CONSTANT (decl) = TREE_CONSTANT (orig_decl);
       TREE_READONLY (decl) = TREE_READONLY (orig_decl);
+      DECL_VIRTUAL_P (decl) = DECL_VIRTUAL_P (orig_decl);
       DECL_ARTIFICIAL (decl) = 1;
       SET_DECL_TEMPLATE_PARM_P (decl);
 
diff --git a/gcc/testsuite/g++.dg/concepts/abbrev7.C b/gcc/testsuite/g++.dg/concepts/abbrev7.C
new file mode 100644
index 00000000000..443c1b7871b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/concepts/abbrev7.C
@@ -0,0 +1,14 @@ 
+// PR c++/96106
+// { dg-do compile { target concepts } }
+
+template<typename>
+struct number {
+  friend void add(auto);
+};
+
+void add(auto) { }
+
+void foo() {
+  number<int> n;
+  add(n); // { dg-bogus "ambiguous" }
+}