commit: 572e86ac9b0838f4e227460fb482166bce46f961 Author: Sam James <sam <AT> gentoo <DOT> org> AuthorDate: Sun Mar 19 21:51:59 2023 +0000 Commit: Sam James <sam <AT> gentoo <DOT> org> CommitDate: Sun Mar 19 21:51:59 2023 +0000 URL: https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=572e86ac
sys-devel/gdb: fix build w/ clang 16 (-Wenum-constexpr-conversion) Closes: https://bugs.gentoo.org/894174 Signed-off-by: Sam James <sam <AT> gentoo.org> ...b-13.1-Wenum-constexpr-conversion-clang16.patch | 128 +++++++++++++++++++++ sys-devel/gdb/gdb-13.1-r1.ebuild | 1 + 2 files changed, 129 insertions(+) diff --git a/sys-devel/gdb/files/gdb-13.1-Wenum-constexpr-conversion-clang16.patch b/sys-devel/gdb/files/gdb-13.1-Wenum-constexpr-conversion-clang16.patch new file mode 100644 index 000000000000..adc09f83ea68 --- /dev/null +++ b/sys-devel/gdb/files/gdb-13.1-Wenum-constexpr-conversion-clang16.patch @@ -0,0 +1,128 @@ +https://bugs.gentoo.org/894174 +https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ae61525fcf456ab395d55c45492a106d1275873a + +From ae61525fcf456ab395d55c45492a106d1275873a Mon Sep 17 00:00:00 2001 +From: Simon Marchi <[email protected]> +Date: Thu, 23 Feb 2023 12:35:40 -0500 +Subject: [PATCH] gdbsupport: ignore -Wenum-constexpr-conversion in + enum-flags.h + +When building with clang 16, we get: + + CXX gdb.o + In file included from /home/smarchi/src/binutils-gdb/gdb/gdb.c:19: + In file included from /home/smarchi/src/binutils-gdb/gdb/defs.h:65: + /home/smarchi/src/binutils-gdb/gdb/../gdbsupport/enum-flags.h:95:52: error: integer value -1 is outside the valid range of values [0, 15] for this enumeration type [-Wenum-constexpr-conversion] + integer_for_size<sizeof (T), static_cast<bool>(T (-1) < T (0))>::type + ^ + +The error message does not make it clear in the context of which enum +flag this fails (i.e. what is T in this context), but it doesn't really +matter, we have similar warning/errors for many of them, if we let the +build go through. + +clang is right that the value -1 is invalid for the enum type we cast -1 +to. However, we do need this expression in order to select an integer +type with the appropriate signedness. That is, with the same signedness +as the underlying type of the enum. + +I first wondered if that was really needed, if we couldn't use +std::underlying_type for that. It turns out that the comment just above +says: + + /* Note that std::underlying_type<enum_type> is not what we want here, + since that returns unsigned int even when the enum decays to signed + int. */ + +I was surprised, because std::is_signed<std::underlying_type<enum_type>> +returns the right thing. So I tried replacing all this with +std::underlying_type, see if that would work. Doing so causes some +build failures in unittests/enum-flags-selftests.c: + + CXX unittests/enum-flags-selftests.o + /home/smarchi/src/binutils-gdb/gdb/unittests/enum-flags-selftests.c:254:1: error: static assertion failed due to requirement 'gdb::is_same<selftests::enum_flags_tests::check_valid_expr254::archetype<enum_flags<s + elftests::enum_flags_tests::RE>, selftests::enum_flags_tests::RE, enum_flags<selftests::enum_flags_tests::RE2>, selftests::enum_flags_tests::RE2, enum_flags<selftests::enum_flags_tests::URE>, selftests::enum_fla + gs_tests::URE, int>, selftests::enum_flags_tests::check_valid_expr254::archetype<enum_flags<selftests::enum_flags_tests::RE>, selftests::enum_flags_tests::RE, enum_flags<selftests::enum_flags_tests::RE2>, selfte + sts::enum_flags_tests::RE2, enum_flags<selftests::enum_flags_tests::URE>, selftests::enum_flags_tests::URE, unsigned int>>::value == true': + CHECK_VALID (true, int, true ? EF () : EF2 ()) + ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + /home/smarchi/src/binutils-gdb/gdb/unittests/enum-flags-selftests.c:91:3: note: expanded from macro 'CHECK_VALID' + CHECK_VALID_EXPR_6 (EF, RE, EF2, RE2, UEF, URE, VALID, EXPR_TYPE, EXPR) + ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + /home/smarchi/src/binutils-gdb/gdb/../gdbsupport/valid-expr.h:105:3: note: expanded from macro 'CHECK_VALID_EXPR_6' + CHECK_VALID_EXPR_INT (ESC_PARENS (typename T1, typename T2, \ + ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + /home/smarchi/src/binutils-gdb/gdb/../gdbsupport/valid-expr.h:66:3: note: expanded from macro 'CHECK_VALID_EXPR_INT' + static_assert (gdb::is_detected_exact<archetype<TYPES, EXPR_TYPE>, \ + ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ + +This is a bit hard to decode, but basically enumerations have the +following funny property that they decay into a signed int, even if +their implicit underlying type is unsigned. This code: + + enum A {}; + enum B {}; + + int main() { + std::cout << std::is_signed<std::underlying_type<A>::type>::value + << std::endl; + std::cout << std::is_signed<std::underlying_type<B>::type>::value + << std::endl; + auto result = true ? A() : B(); + std::cout << std::is_signed<decltype(result)>::value << std::endl; + } + +produces: + + 0 + 0 + 1 + +So, the "CHECK_VALID" above checks that this property works for enum flags the +same way as it would if you were using their underlying enum types. And +somehow, changing integer_for_size to use std::underlying_type breaks that. + +Since the current code does what we want, and I don't see any way of doing it +differently, ignore -Wenum-constexpr-conversion around it. + +Change-Id: Ibc82ae7bbdb812102ae3f1dd099fc859dc6f3cc2 +--- a/gdbsupport/enum-flags.h ++++ b/gdbsupport/enum-flags.h +@@ -91,9 +91,12 @@ template<> struct integer_for_size<8, 1> { typedef int64_t type; }; + template<typename T> + struct enum_underlying_type + { ++ DIAGNOSTIC_PUSH ++ DIAGNOSTIC_IGNORE_ENUM_CONSTEXPR_CONVERSION + typedef typename + integer_for_size<sizeof (T), static_cast<bool>(T (-1) < T (0))>::type + type; ++ DIAGNOSTIC_POP + }; + + namespace enum_flags_detail +--- a/include/diagnostics.h ++++ b/include/diagnostics.h +@@ -76,6 +76,11 @@ + # define DIAGNOSTIC_ERROR_SWITCH \ + DIAGNOSTIC_ERROR ("-Wswitch") + ++# if __has_warning ("-Wenum-constexpr-conversion") ++# define DIAGNOSTIC_IGNORE_ENUM_CONSTEXPR_CONVERSION \ ++ DIAGNOSTIC_IGNORE ("-Wenum-constexpr-conversion") ++# endif ++ + #elif defined (__GNUC__) /* GCC */ + + # define DIAGNOSTIC_IGNORE_DEPRECATED_DECLARATIONS \ +@@ -155,4 +160,8 @@ + # define DIAGNOSTIC_ERROR_SWITCH + #endif + ++#ifndef DIAGNOSTIC_IGNORE_ENUM_CONSTEXPR_CONVERSION ++# define DIAGNOSTIC_IGNORE_ENUM_CONSTEXPR_CONVERSION ++#endif ++ + #endif /* DIAGNOSTICS_H */ +-- +2.31.1 diff --git a/sys-devel/gdb/gdb-13.1-r1.ebuild b/sys-devel/gdb/gdb-13.1-r1.ebuild index bc86849c6276..60adac18680f 100644 --- a/sys-devel/gdb/gdb-13.1-r1.ebuild +++ b/sys-devel/gdb/gdb-13.1-r1.ebuild @@ -101,6 +101,7 @@ BDEPEND=" PATCHES=( "${FILESDIR}"/${PN}-8.3.1-verbose-build.patch + "${FILESDIR}"/${P}-Wenum-constexpr-conversion-clang16.patch ) pkg_setup() {
