v4-0001-Make-copyObject-work-in-C.patch

From 290a1ab7788756adaed14dc2b483156d65bc3b95 Mon Sep 17 00:00:00 2001
From: Jelte Fennema-Nio <postgres@jeltef.nl>
Date: Fri, 5 Dec 2025 15:37:59 +0100
Subject: [PATCH v4 1/4] Make copyObject work in C++

Calling copyObject in C++ without GNU extensions fails with an error
like this:

error: use of undeclared identifier 'typeof'; did you mean 'typeid'

This is due to the C compiler supporting used to compile postgres
supporting typeof, but that function actually not being present in the
C++ compiler. This fixes that by defining pg_exprtype which maps to
typeof or decltype depending on the compiler. While pg_typeof would have
been a more natural name, that name is already taken in our codebase as
the implementation of the pg_typeof UDF.
---
 src/include/c.h           | 13 +++++++++++++
 src/include/nodes/nodes.h |  4 ++--
 2 files changed, 15 insertions(+), 2 deletions(-)

diff --git a/src/include/c.h b/src/include/c.h
index 77c754a904a..18bd50da510 100644
--- a/src/include/c.h
+++ b/src/include/c.h
@@ -418,6 +418,19 @@
 #define unlikely(x) ((x) != 0)
 #endif
 
+/*
+ * pg_exprtype
+ *		Get the type of an expression at compile time.
+ *
+ * In C++ we use decltype since typeof is not standard C++, while in C we use
+ * typeof when available.
+ */
+#if defined(__cplusplus)
+#define pg_exprtype(x) decltype(x)
+#elif defined(HAVE_TYPEOF)
+#define pg_exprtype(x) typeof(x)
+#endif
+
 /*
  * CppAsString
  *		Convert the argument to a string, using the C preprocessor.
diff --git a/src/include/nodes/nodes.h b/src/include/nodes/nodes.h
index b6ad28618ab..f5e17e670b7 100644
--- a/src/include/nodes/nodes.h
+++ b/src/include/nodes/nodes.h
@@ -226,8 +226,8 @@ extern int16 *readAttrNumberCols(int numCols);
 extern void *copyObjectImpl(const void *from);
 
 /* cast result back to argument type, if supported by compiler */
-#ifdef HAVE_TYPEOF
-#define copyObject(obj) ((typeof(obj)) copyObjectImpl(obj))
+#ifdef pg_exprtype
+#define copyObject(obj) ((pg_exprtype(obj)) copyObjectImpl(obj))
 #else
 #define copyObject(obj) copyObjectImpl(obj)
 #endif

base-commit: 094b61ce3ebbb1258675cb9b4eca9198628e2177
-- 
2.52.0