From 6f04937e1d7db190ca96ec08d8aeb25f0ec6e994 Mon Sep 17 00:00:00 2001 From: Tom de Vries Date: Fri, 10 Jan 2025 08:40:11 +0100 Subject: [gdb/build, c++20] Fix build with gcc 10 With gcc 10 and -std=c++20, we run into the same problem as reported in commit 6feae66da1d ("[gdb/build, c++20] Handle deprecated std::allocator::construct"). The problem was fixed using: ... -template> +template= 202002L + = std::pmr::polymorphic_allocator +#else + = std::allocator +#endif + > ... but that doesn't work for gcc 10, because it defines __cplusplus differently: ... $ echo | g++-10 -E -dD -x c++ - -std=c++20 2>&1 | grep __cplusplus #define __cplusplus 201709L $ echo | g++-11 -E -dD -x c++ - -std=c++20 2>&1 | grep __cplusplus #define __cplusplus 202002L ... Fix this by using the library feature test macro __cpp_lib_polymorphic_allocator [1], which is undefined for c++17 and defined for c++20: ... $ echo | g++-10 -E -dD -x c++ - -include memory_resource -std=c++17 2>&1 \ | grep __cpp_lib_polymorphic_allocator $ echo | g++-10 -E -dD -x c++ - -include memory_resource -std=c++20 2>&1 \ | grep __cpp_lib_polymorphic_allocator #define __cpp_lib_polymorphic_allocator 201902L $ ... A similar problem exists for commit 3173529d7de ("[gdb/guile, c++20] Work around Werror=volatile in libguile.h"). Fix this by testing for 201709L instead. Tested on x86_64-linux, by building gdb with {gcc 10, clang 17.0.6} x {-std=c++17, -std=c++20}. PR build/32503 Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=32503 Approved-By: Tom Tromey [1] https://en.cppreference.com/w/cpp/feature_test#cpp_lib_polymorphic_allocator --- gdb/guile/guile-internal.h | 8 +++++++- 1 file changed, 7 insertions(+), 1 deletion(-) (limited to 'gdb/guile/guile-internal.h') diff --git a/gdb/guile/guile-internal.h b/gdb/guile/guile-internal.h index 8d83b8b..1057b83 100644 --- a/gdb/guile/guile-internal.h +++ b/gdb/guile/guile-internal.h @@ -30,7 +30,13 @@ #include "objfiles.h" #include "top.h" -#if __cplusplus >= 202002L +/* GCC introduced C++20 support in GCC 8, using -std=c++2a (the name of the + C++20 standard before publishing) and __cplusplus 201709L. In GCC 10, + -std=c++20 was added, but __cplusplus stayed at 201709L, and was only + changed to the standard 202002L in GCC 11. Consequently, some C++20 + features and restrictions need to be tested against the non-standard + 201709L, otherwise the build with GCC 10 and -std=c++20 will break. */ +#if __cplusplus >= 201709L /* Work around Werror=volatile in SCM_UNPACK for SCM_DEBUG_TYPING_STRICTNESS == 1. Reported upstream: https://debbugs.gnu.org/cgi/bugreport.cgi?bug=65333 . */ -- cgit v1.1