--- /dev/null
+From e3b59e5461c81f03b608f24388af716c1983e2d0 Mon Sep 17 00:00:00 2001
+From: Simon Marchi <simon.marchi@efficios.com>
+Date: Thu, 23 Feb 2023 17:35:40 +0000
+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
+---
+ gdbsupport/enum-flags.h | 3 +++
+ include/diagnostics.h | 9 +++++++++
+ 2 files changed, 12 insertions(+)
+
+--- a/gdbsupport/enum-flags.h
++++ b/gdbsupport/enum-flags.h
+@@ -91,9 +91,12 @@ template<> struct integer_for_size<8, 1>
+ 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
+@@ -66,6 +66,11 @@
+ # 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 */
+
+ # if __GNUC__ >= 7
+@@ -96,6 +101,10 @@
+ # define DIAGNOSTIC_IGNORE_DEPRECATED_DECLARATIONS
+ #endif
+
++#ifndef DIAGNOSTIC_IGNORE_ENUM_CONSTEXPR_CONVERSION
++# define DIAGNOSTIC_IGNORE_ENUM_CONSTEXPR_CONVERSION
++#endif
++
+ #ifndef DIAGNOSTIC_IGNORE_DEPRECATED_REGISTER
+ # define DIAGNOSTIC_IGNORE_DEPRECATED_REGISTER
+ #endif
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