From 1887d822f1428637c935b9f5e8be4a2a56fb77c7 Mon Sep 17 00:00:00 2001 From: Peter Eisentraut Date: Mon, 2 Mar 2026 11:46:02 +0100 Subject: [PATCH] Support using copyObject in standard C++ Calling copyObject in C++ without GNU extensions (e.g. when using -std=c++11 instead of -std=gnu++11) fails with an error like this: error: use of undeclared identifier 'typeof'; did you mean 'typeid' This is due to the C compiler used to compile PostgreSQL supporting typeof, but that function actually not being present in the C++ compiler. This fixes that by explicitely checking for typeof support in C++, and then either use that or define typeof ourselves as: std::remove_reference_t According to the paper that led to adding typeof to the C standard, that's the C++ equivalent of the C typeof: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2927.htm#existing-decltype Author: Author: Jelte Fennema-Nio Discussion: https://www.postgresql.org/message-id/flat/DGPW5WCFY7WY.1IHCDNIVVT300%2540jeltef.nl --- config/c-compiler.m4 | 29 ++++++++++ configure | 54 +++++++++++++++++++ configure.ac | 1 + meson.build | 25 +++++++++ src/include/c.h | 21 ++++++++ src/include/pg_config.h.in | 7 +++ .../test_cplusplusext/test_cplusplusext.cpp | 2 + 7 files changed, 139 insertions(+) diff --git a/config/c-compiler.m4 b/config/c-compiler.m4 index 1509dbfa2ab..5b3cbc7e8e8 100644 --- a/config/c-compiler.m4 +++ b/config/c-compiler.m4 @@ -193,6 +193,35 @@ fi])# PGAC_C_TYPEOF +# PGAC_CXX_TYPEOF +# ---------------- +# Check if the C++ compiler understands typeof or a variant. Define +# HAVE_CXX_TYPEOF if so, and define 'pg_cxx_typeof' to the actual key word. +# +AC_DEFUN([PGAC_CXX_TYPEOF], +[AC_CACHE_CHECK(for C++ typeof, pgac_cv_cxx_typeof, +[pgac_cv_cxx_typeof=no +AC_LANG_PUSH(C++) +for pgac_kw in typeof __typeof__; do + AC_COMPILE_IFELSE([AC_LANG_PROGRAM([], +[int x = 0; +$pgac_kw(x) y; +y = x; +return y;])], +[pgac_cv_cxx_typeof=$pgac_kw]) + test "$pgac_cv_cxx_typeof" != no && break +done +AC_LANG_POP([])]) +if test "$pgac_cv_cxx_typeof" != no; then + AC_DEFINE(HAVE_CXX_TYPEOF, 1, + [Define to 1 if your C++ compiler understands `typeof' or something similar.]) + if test "$pgac_cv_cxx_typeof" != typeof; then + AC_DEFINE_UNQUOTED(pg_cxx_typeof, $pgac_cv_cxx_typeof, [Define to how the C++ compiler spells `typeof'.]) + fi +fi])# PGAC_CXX_TYPEOF + + + # PGAC_C_TYPES_COMPATIBLE # ----------------------- # Check if the C compiler understands __builtin_types_compatible_p, diff --git a/configure b/configure index ec4798fe519..b30b98a586e 100755 --- a/configure +++ b/configure @@ -15078,6 +15078,60 @@ _ACEOF fi fi +{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for C++ typeof" >&5 +$as_echo_n "checking for C++ typeof... " >&6; } +if ${pgac_cv_cxx_typeof+:} false; then : + $as_echo_n "(cached) " >&6 +else + pgac_cv_cxx_typeof=no +ac_ext=cpp +ac_cpp='$CXXCPP $CPPFLAGS' +ac_compile='$CXX -c $CXXFLAGS $CPPFLAGS conftest.$ac_ext >&5' +ac_link='$CXX -o conftest$ac_exeext $CXXFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5' +ac_compiler_gnu=$ac_cv_cxx_compiler_gnu + +for pgac_kw in typeof __typeof__; do + cat confdefs.h - <<_ACEOF >conftest.$ac_ext +/* end confdefs.h. */ + +int +main () +{ +int x = 0; +$pgac_kw(x) y; +y = x; +return y; + ; + return 0; +} +_ACEOF +if ac_fn_cxx_try_compile "$LINENO"; then : + pgac_cv_cxx_typeof=$pgac_kw +fi +rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext + test "$pgac_cv_cxx_typeof" != no && break +done +ac_ext=c +ac_cpp='$CPP $CPPFLAGS' +ac_compile='$CC -c $CFLAGS $CPPFLAGS conftest.$ac_ext >&5' +ac_link='$CC -o conftest$ac_exeext $CFLAGS $CPPFLAGS $LDFLAGS conftest.$ac_ext $LIBS >&5' +ac_compiler_gnu=$ac_cv_c_compiler_gnu + +fi +{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $pgac_cv_cxx_typeof" >&5 +$as_echo "$pgac_cv_cxx_typeof" >&6; } +if test "$pgac_cv_cxx_typeof" != no; then + +$as_echo "#define HAVE_CXX_TYPEOF 1" >>confdefs.h + + if test "$pgac_cv_cxx_typeof" != typeof; then + +cat >>confdefs.h <<_ACEOF +#define pg_cxx_typeof $pgac_cv_cxx_typeof +_ACEOF + + fi +fi { $as_echo "$as_me:${as_lineno-$LINENO}: checking for __builtin_types_compatible_p" >&5 $as_echo_n "checking for __builtin_types_compatible_p... " >&6; } if ${pgac_cv__types_compatible+:} false; then : diff --git a/configure.ac b/configure.ac index b2f6fdbe6ac..f4e3bd307c8 100644 --- a/configure.ac +++ b/configure.ac @@ -1732,6 +1732,7 @@ PGAC_PRINTF_ARCHETYPE PGAC_CXX_PRINTF_ARCHETYPE PGAC_C_STATEMENT_EXPRESSIONS PGAC_C_TYPEOF +PGAC_CXX_TYPEOF PGAC_C_TYPES_COMPATIBLE PGAC_C_BUILTIN_CONSTANT_P PGAC_C_BUILTIN_OP_OVERFLOW diff --git a/meson.build b/meson.build index 3ee8c2325f9..ddf5172982f 100644 --- a/meson.build +++ b/meson.build @@ -2953,6 +2953,31 @@ int main(void) endif endforeach +# Check if the C++ compiler understands typeof or a variant. +if have_cxx + foreach kw : ['typeof', '__typeof__'] + if cxx.compiles(''' +int main(void) +{ + int x = 0; + @0@(x) y; + y = x; + return y; +} +'''.format(kw), + name: 'C++ ' + kw, + args: test_c_args, include_directories: postgres_inc) + + cdata.set('HAVE_CXX_TYPEOF', 1) + if kw != 'typeof' + cdata.set('pg_cxx_typeof', kw) + endif + + break + endif + endforeach +endif + # MSVC doesn't cope well with defining restrict to __restrict, the # spelling it understands, because it conflicts with diff --git a/src/include/c.h b/src/include/c.h index fb0ea1bc680..a4fee84398d 100644 --- a/src/include/c.h +++ b/src/include/c.h @@ -424,6 +424,27 @@ #define unlikely(x) ((x) != 0) #endif +/* + * Provide typeof in C++ for C++ compilers that don't support typeof natively. + * It might be spelled __typeof__ instead of typeof, in which case + * pg_cxx_typeof provides that mapping. If neither is supported, we can use + * decltype, but to make it equivalent to C's typeof, we need to remove + * references from the result [1]. Also ensure HAVE_TYPEOF is set so that + * typeof-dependent code is always enabled in C++ mode. + * + * [1]: https://www.open-std.org/jtc1/sc22/wg14/www/docs/n2927.htm#existing-decltype + */ +#if defined(__cplusplus) +#ifdef pg_cxx_typeof +#define typeof(x) pg_cxx_typeof(x) +#elif !defined(HAVE_CXX_TYPEOF) +#define typeof(x) std::remove_reference_t +#endif +#ifndef HAVE_TYPEOF +#define HAVE_TYPEOF 1 +#endif +#endif + /* * CppAsString * Convert the argument to a string, using the C preprocessor. diff --git a/src/include/pg_config.h.in b/src/include/pg_config.h.in index 538822cbc70..f64b198738b 100644 --- a/src/include/pg_config.h.in +++ b/src/include/pg_config.h.in @@ -69,6 +69,10 @@ /* Define to 1 if you have the header file. */ #undef HAVE_CRTDEFS_H +/* Define to 1 if your C++ compiler understands `typeof' or something similar. + */ +#undef HAVE_CXX_TYPEOF + /* Define to 1 if you have the declaration of `fdatasync', and to 0 if you don't. */ #undef HAVE_DECL_FDATASYNC @@ -780,6 +784,9 @@ /* Define for large files, on AIX-style hosts. */ #undef _LARGE_FILES +/* Define to how the C++ compiler spells `typeof'. */ +#undef pg_cxx_typeof + /* Define to keyword to use for C99 restrict support, or to nothing if not supported */ #undef pg_restrict diff --git a/src/test/modules/test_cplusplusext/test_cplusplusext.cpp b/src/test/modules/test_cplusplusext/test_cplusplusext.cpp index eb129dd15d4..ea04a761184 100644 --- a/src/test/modules/test_cplusplusext/test_cplusplusext.cpp +++ b/src/test/modules/test_cplusplusext/test_cplusplusext.cpp @@ -37,6 +37,7 @@ 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); List *list = list_make1(node); foreach_ptr(RangeTblRef, rtr, list) @@ -54,6 +55,7 @@ test_cplusplus_add(PG_FUNCTION_ARGS) list_free(list); pfree(node); + pfree(copy); switch (a) {