From ae61525fcf456ab395d55c45492a106d1275873a Mon Sep 17 00:00:00 2001 From: Simon Marchi Date: Thu, 23 Feb 2023 12:35:40 -0500 Subject: 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(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 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> 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::RE, enum_flags, selftests::enum_flags_tests::RE2, enum_flags, selftests::enum_fla gs_tests::URE, int>, selftests::enum_flags_tests::check_valid_expr254::archetype, selftests::enum_flags_tests::RE, enum_flags, selfte sts::enum_flags_tests::RE2, enum_flags, 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, \ ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 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::type>::value << std::endl; std::cout << std::is_signed::type>::value << std::endl; auto result = true ? A() : B(); std::cout << std::is_signed::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 --- include/diagnostics.h | 9 +++++++++ 1 file changed, 9 insertions(+) (limited to 'include/diagnostics.h') diff --git a/include/diagnostics.h b/include/diagnostics.h index d3ff27b..41e6db6 100644 --- 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 */ -- cgit v1.1