From 2d7130aab09383c88ca8c98d666144df70d0f2da Mon Sep 17 00:00:00 2001 From: Jelte Fennema-Nio Date: Fri, 5 Dec 2025 15:37:59 +0100 Subject: [PATCH v7 2/5] Support using copyObject 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 ++-- .../modules/test_cplusplusext/test_cplusplusext.cpp | 6 ++++++ 3 files changed, 21 insertions(+), 2 deletions(-) diff --git a/src/include/c.h b/src/include/c.h index c0be07a4566..08490641906 100644 --- a/src/include/c.h +++ b/src/include/c.h @@ -412,6 +412,19 @@ #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 diff --git a/src/test/modules/test_cplusplusext/test_cplusplusext.cpp b/src/test/modules/test_cplusplusext/test_cplusplusext.cpp index 7108e5b1cc5..48741f27949 100644 --- a/src/test/modules/test_cplusplusext/test_cplusplusext.cpp +++ b/src/test/modules/test_cplusplusext/test_cplusplusext.cpp @@ -17,6 +17,7 @@ extern "C" { #include "postgres.h" #include "fmgr.h" +#include "nodes/parsenodes.h" PG_MODULE_MAGIC_EXT("test_cplusplusext", "1.2"); @@ -32,6 +33,11 @@ test_cplusplus_add(PG_FUNCTION_ARGS) { int32 a = PG_GETARG_INT32(0); int32 b = PG_GETARG_INT32(1); + RangeTblRef *node = makeNode(RangeTblRef); + RangeTblRef *copy = copyObject(node); + + pfree(copy); + pfree(node); PG_RETURN_INT32(a + b); } -- 2.52.0