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devel/gdb: fix build with clang 16
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Clang 16 has a new error about integer values being outside the valid
range for enum types, which shows up when building gdb:

  In file included from /wrkdirs/usr/ports/devel/gdb/work-py39/gdb-13.1/gdb/x86-fbsd-nat.c:20:
  In file included from /wrkdirs/usr/ports/devel/gdb/work-py39/gdb-13.1/gdb/defs.h:65:
  /wrkdirs/usr/ports/devel/gdb/work-py39/gdb-13.1/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
                                                     ^
  In file included from /wrkdirs/usr/ports/devel/gdb/work-py39/gdb-13.1/gdb/x86-bsd-nat.c:20:
  In file included from /wrkdirs/usr/ports/devel/gdb/work-py39/gdb-13.1/gdb/defs.h:65:
  /wrkdirs/usr/ports/devel/gdb/work-py39/gdb-13.1/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
                                                     ^
  In file included from /wrkdirs/usr/ports/devel/gdb/work-py39/gdb-13.1/gdb/x86-nat.c:20:
  In file included from /wrkdirs/usr/ports/devel/gdb/work-py39/gdb-13.1/gdb/defs.h:65:
  /wrkdirs/usr/ports/devel/gdb/work-py39/gdb-13.1/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
                                                     ^
  In file included from /wrkdirs/usr/ports/devel/gdb/work-py39/gdb-13.1/gdb/windows-tdep.c:18:
  In file included from /wrkdirs/usr/ports/devel/gdb/work-py39/gdb-13.1/gdb/defs.h:65:
  /wrkdirs/usr/ports/devel/gdb/work-py39/gdb-13.1/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
                                                     ^

Upstream already noticed this, and committed
https://sourceware.org/git/?p=binutils-gdb.git;a=commit;h=ae61525fcf4 as
a workaround, so add this as an additional patch, until gdb 13.2 is
released.

PR:		271045
Approved by:	maintainer timeout (2 weeks)
MFH:		2023Q2
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@DimitryAndric
DimitryAndric committed May 7, 2023
1 parent 9d2bf7a commit 9e765fe
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3 changes: 2 additions & 1 deletion devel/gdb/Makefile
View file
@@ -1,6 +1,6 @@
PORTNAME= gdb
DISTVERSION= 13.1
PORTREVISION= 1
PORTREVISION= 2
CATEGORIES= devel
MASTER_SITES= GNU

Expand Down Expand Up @@ -36,6 +36,7 @@ CFLAGS+= -DRL_NO_COMPAT
EXCLUDE= dejagnu expect sim texinfo intl
EXTRACT_AFTER_ARGS= ${EXCLUDE:S/^/--exclude /}
EXTRA_PATCHES= ${FILESDIR}/commit-a980a7d24b9
EXTRA_PATCHES+= ${FILESDIR}/commit-ae61525fcf4

VER= ${DISTVERSION:S/.//g}
PLIST_SUB= VER=${VER}
Expand Down
128 changes: 128 additions & 0 deletions devel/gdb/files/commit-ae61525fcf4
View file
@@ -0,0 +1,128 @@
commit ae61525fcf456ab395d55c45492a106d1275873a
Author: Simon Marchi <simon.marchi@efficios.com>
Date: 2023-02-23 12:35:40 -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.

Change-Id: Ibc82ae7bbdb812102ae3f1dd099fc859dc6f3cc2

diff --git gdbsupport/enum-flags.h gdbsupport/enum-flags.h
index 700037f6126..41ac7838f06 100644
--- gdbsupport/enum-flags.h
+++ 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
diff --git include/diagnostics.h include/diagnostics.h
index d3ff27bc008..41e6db65391 100644
--- include/diagnostics.h
+++ 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 */

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