Thank you for the patch!
On 12/22/25 3:19 AM, Alex Yesmanchyk wrote:
Consider the following pr38612.cc file:
Your patch should add this to the testsuite.
--
struct Base {};
struct X; // X derived from Base later but incomplete here
struct Y {}; // Y not derived from Base
int test1(int Base::* p2m, X* object)
{
return object->*p2m; // fails because X is incomplete
}
struct X : Base
{
};
int test2(int Base::* p2m, X* object)
{
return object->*p2m; // OK
}
int test3(int Base::* p2m, Y* object)
{
return object->*p2m; // fails because Y is not derived from Base
}
--
Now for test1 and test3 it produces the following errors:
pr38612.cc: In function 'int test1(int Base::*, X*)':
pr38612.cc:8:21: error: pointer to member type 'int' incompatible \
with incomplete object type 'X'
This is an existing issue, but printing 'int' here is wrong, it should
be 'int Base::*'. That seems to be a matter of passing ptrmem_type to
the error call instead of type.
8 | return object->*p2m; // fails because X is incomplete
| ^~~
pr38612.cc: In function 'int test3(int Base::*, Y*)':
pr38612.cc:22:21: error: pointer to member type 'int' incompatible \
with object type 'Y' because 'Y' is not derived from 'Base'
Likewise.
You also need ChangeLog entries for your patch.
I've adjusted your patch as follows; any objection?
From d4a8a5fdd52ec46f9f694f60b12f18c7cdbaf27d Mon Sep 17 00:00:00 2001
From: Alex Yesmanchyk <[email protected]>
Date: Mon, 26 Jan 2026 18:16:53 +0800
Subject: [PATCH] c++: Error diagnostics for pointer-to-member type [PR38612]
To: [email protected]
Consider the following ptrtomem4.C file.
Now for test1 and test3 it produces the following errors:
ptrtomem4.C: In function 'int test1(int Base::*, X*)':
ptrtomem4.C:8:21: error: pointer to member type 'int' incompatible with incomplete object type 'X'
ptrtomem4.C: In function 'int test3(int Base::*, Y*)':
ptrtomem4.C:22:21: error: pointer to member type 'int' incompatible with object type 'Y' because 'Y' is not derived from 'Base'
PR c++/38612
gcc/cp/ChangeLog:
* typeck2.cc (build_m_component_ref): Improve class mismatch
diagnostic.
gcc/testsuite/ChangeLog:
* g++.dg/diagnostic/ptrtomem4.C: New test.
Signed-off-by: Alex Yesmanchyk <[email protected]>
Co-authored-by: Jason Merrill <[email protected]>
---
gcc/cp/typeck2.cc | 12 +++++++++--
gcc/testsuite/g++.dg/diagnostic/ptrtomem4.C | 24 +++++++++++++++++++++
2 files changed, 34 insertions(+), 2 deletions(-)
create mode 100644 gcc/testsuite/g++.dg/diagnostic/ptrtomem4.C
diff --git a/gcc/cp/typeck2.cc b/gcc/cp/typeck2.cc
index 1e5e3b24a23..f18c5a7499e 100644
--- a/gcc/cp/typeck2.cc
+++ b/gcc/cp/typeck2.cc
@@ -2459,8 +2459,16 @@ build_m_component_ref (tree datum, tree component, tsubst_flags_t complain)
{
mismatch:
if (complain & tf_error)
- error ("pointer to member type %qT incompatible with object "
- "type %qT", type, objtype);
+ {
+ if (COMPLETE_TYPE_P (objtype))
+ error ("pointer to member type %qT incompatible "
+ "with object type %qT because %qT is not "
+ "derived from %qT", ptrmem_type, objtype,
+ objtype, ctype);
+ else
+ error ("pointer to member type %qT incompatible with "
+ "incomplete object type %qT", ptrmem_type, objtype);
+ }
return error_mark_node;
}
else if (binfo == error_mark_node)
diff --git a/gcc/testsuite/g++.dg/diagnostic/ptrtomem4.C b/gcc/testsuite/g++.dg/diagnostic/ptrtomem4.C
new file mode 100644
index 00000000000..564c28b4300
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/ptrtomem4.C
@@ -0,0 +1,24 @@
+// PR c++/38612
+
+struct Base {};
+struct X; // X derived from Base later but incomplete here
+struct Y {}; // Y not derived from Base
+
+int test1(int Base::* p2m, X* object)
+{
+ return object->*p2m; // { dg-error "int Base::.' incompatible with incomplete object type 'X'" }
+}
+
+struct X : Base
+{
+};
+
+int test2(int Base::* p2m, X* object)
+{
+ return object->*p2m; // OK
+}
+
+int test3(int Base::* p2m, Y* object)
+{
+ return object->*p2m; // { dg-error "int Base::.' incompatible with object type 'Y' because 'Y' is not derived from 'Base'" }
+}
--
2.52.0
