Building GDB 13.1 with clang 16, I get these warnings: 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:66: /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 ^ This breaks the build, since clang makes -Wenum-constexpr-conversion an error by default (without -Werror). Then, we have a few of these warnings: CXX z80-tdep.o /home/smarchi/src/binutils-gdb/gdb/z80-tdep.c:338:32: warning: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Wsingle-bit-bitfield-constant-conversion] info->prologue_type.load_args = 1; ^ ~ We have patches for these issues in master: https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ae61525fcf456ab395d55c45492a106d1275873a https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=07f285934886016ddd82cac99a3873e68b499d5c We can consider cherry-picking them in gdb-13-branch.
Setting the target milestone.
The gdb-13-branch branch has been updated by Simon Marchi <simark@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=12e3f3bc6ec74eb50e04675f5bcf962482d3ff25 commit 12e3f3bc6ec74eb50e04675f5bcf962482d3ff25 Author: Simon Marchi <simon.marchi@efficios.com> Date: Thu Feb 23 12:35:40 2023 -0500 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. (cherry picked from commit ae61525fcf456ab395d55c45492a106d1275873a) Change-Id: Ibc82ae7bbdb812102ae3f1dd099fc859dc6f3cc2 Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30423 Approved-By: Tom Tromey <tom@tromey.com>
The gdb-13-branch branch has been updated by Simon Marchi <simark@sourceware.org>: https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;h=caaf38247f0c5e9a7d20d5aaa4ece0b3482f65f9 commit caaf38247f0c5e9a7d20d5aaa4ece0b3482f65f9 Author: Simon Marchi <simon.marchi@efficios.com> Date: Thu Feb 23 12:35:41 2023 -0500 gdb: fix -Wsingle-bit-bitfield-constant-conversion warning in z80-tdep.c When building with clang 16, I see: /home/smarchi/src/binutils-gdb/gdb/z80-tdep.c:338:32: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion] info->prologue_type.load_args = 1; ^ ~ /home/smarchi/src/binutils-gdb/gdb/z80-tdep.c:345:36: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion] info->prologue_type.critical = 1; ^ ~ /home/smarchi/src/binutils-gdb/gdb/z80-tdep.c:351:37: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion] info->prologue_type.interrupt = 1; ^ ~ /home/smarchi/src/binutils-gdb/gdb/z80-tdep.c:367:36: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion] info->prologue_type.fp_sdcc = 1; ^ ~ /home/smarchi/src/binutils-gdb/gdb/z80-tdep.c:375:35: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion] info->prologue_type.fp_sdcc = 1; ^ ~ /home/smarchi/src/binutils-gdb/gdb/z80-tdep.c:380:35: error: implicit truncation from 'int' to a one-bit wide bit-field changes value from 1 to -1 [-Werror,-Wsingle-bit-bitfield-constant-conversion] info->prologue_type.fp_sdcc = 1; ^ ~ Fix that by using "unsigned int" as the bitfield's underlying type. (cherry picked from commit 07f285934886016ddd82cac99a3873e68b499d5c) Change-Id: I3550a0112f993865dc70b18f02ab11bb5012693d Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=30423 Approved-By: Tom Tromey <tom@tromey.com>
Fixed by those patches.