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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
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| .. | ||
| aout | ||
| cgen | ||
| coff | ||
| elf | ||
| gdb | ||
| mach-o | ||
| opcode | ||
| sim | ||
| som | ||
| vms | ||
| alloca-conf.h | ||
| ansidecl.h | ||
| bfdlink.h | ||
| binary-io.h | ||
| bout.h | ||
| ChangeLog | ||
| ChangeLog-0415 | ||
| ChangeLog-2016 | ||
| ChangeLog-2017 | ||
| ChangeLog-2018 | ||
| ChangeLog-2019 | ||
| ChangeLog-2020 | ||
| ChangeLog-9103 | ||
| collectorAPI.h | ||
| COPYING | ||
| COPYING3 | ||
| ctf-api.h | ||
| ctf.h | ||
| demangle.h | ||
| diagnostics.h | ||
| dis-asm.h | ||
| dwarf2.def | ||
| dwarf2.h | ||
| dyn-string.h | ||
| environ.h | ||
| fibheap.h | ||
| filenames.h | ||
| floatformat.h | ||
| fnmatch.h | ||
| fopen-bin.h | ||
| fopen-same.h | ||
| fopen-vms.h | ||
| gcc-c-fe.def | ||
| gcc-c-interface.h | ||
| gcc-cp-fe.def | ||
| gcc-cp-interface.h | ||
| gcc-interface.h | ||
| getopt.h | ||
| hashtab.h | ||
| hp-symtab.h | ||
| leb128.h | ||
| libcollector.h | ||
| libfcollector.h | ||
| libiberty.h | ||
| longlong.h | ||
| lto-symtab.h | ||
| MAINTAINERS | ||
| md5.h | ||
| oasys.h | ||
| objalloc.h | ||
| obstack.h | ||
| os9k.h | ||
| partition.h | ||
| plugin-api.h | ||
| safe-ctype.h | ||
| sframe-api.h | ||
| sframe.h | ||
| sha1.h | ||
| simple-object.h | ||
| sort.h | ||
| splay-tree.h | ||
| symcat.h | ||
| timeval-utils.h | ||
| vtv-change-permission.h | ||
| xregex2.h | ||
| xregex.h | ||
| xtensa-config.h | ||
| xtensa-dynconfig.h | ||
| xtensa-isa-internal.h | ||
| xtensa-isa.h | ||