* [PATCH 1/2] gdbsupport: ignore -Wenum-constexpr-conversion in enum-flags.h
2023-05-05 15:48 [PATCH 0/2] Cherry-pick patches to build with Clang 16 to gdb-13-branch Simon Marchi
@ 2023-05-05 15:48 ` Simon Marchi
2023-05-05 15:48 ` [PATCH 2/2] gdb: fix -Wsingle-bit-bitfield-constant-conversion warning in z80-tdep.c Simon Marchi
2023-05-05 19:14 ` [PATCH 0/2] Cherry-pick patches to build with Clang 16 to gdb-13-branch Tom Tromey
2 siblings, 0 replies; 5+ messages in thread
From: Simon Marchi @ 2023-05-05 15:48 UTC (permalink / raw)
To: gdb-patches; +Cc: Simon Marchi
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
---
gdbsupport/enum-flags.h | 3 +++
include/diagnostics.h | 9 +++++++++
2 files changed, 12 insertions(+)
diff --git a/gdbsupport/enum-flags.h b/gdbsupport/enum-flags.h
index 440ffe097343..947d47730522 100644
--- a/gdbsupport/enum-flags.h
+++ b/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 a/include/diagnostics.h b/include/diagnostics.h
index 3a75f4e27191..c164e7bd9f49 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 */
--
2.40.1
^ permalink raw reply [flat|nested] 5+ messages in thread* [PATCH 2/2] gdb: fix -Wsingle-bit-bitfield-constant-conversion warning in z80-tdep.c
2023-05-05 15:48 [PATCH 0/2] Cherry-pick patches to build with Clang 16 to gdb-13-branch Simon Marchi
2023-05-05 15:48 ` [PATCH 1/2] gdbsupport: ignore -Wenum-constexpr-conversion in enum-flags.h Simon Marchi
@ 2023-05-05 15:48 ` Simon Marchi
2023-05-05 19:14 ` [PATCH 0/2] Cherry-pick patches to build with Clang 16 to gdb-13-branch Tom Tromey
2 siblings, 0 replies; 5+ messages in thread
From: Simon Marchi @ 2023-05-05 15:48 UTC (permalink / raw)
To: gdb-patches; +Cc: Simon Marchi
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
---
gdb/z80-tdep.c | 10 +++++-----
1 file changed, 5 insertions(+), 5 deletions(-)
diff --git a/gdb/z80-tdep.c b/gdb/z80-tdep.c
index aa296c7169f6..2af6198ff3fc 100644
--- a/gdb/z80-tdep.c
+++ b/gdb/z80-tdep.c
@@ -98,11 +98,11 @@ struct z80_unwind_cache
struct
{
- int called:1; /* there is return address on stack */
- int load_args:1; /* prologues loads args using POPs */
- int fp_sdcc:1; /* prologue saves and adjusts frame pointer IX */
- int interrupt:1; /* __interrupt handler */
- int critical:1; /* __critical function */
+ unsigned int called : 1; /* there is return address on stack */
+ unsigned int load_args : 1; /* prologues loads args using POPs */
+ unsigned int fp_sdcc : 1; /* prologue saves and adjusts frame pointer IX */
+ unsigned int interrupt : 1; /* __interrupt handler */
+ unsigned int critical : 1; /* __critical function */
} prologue_type;
/* Table indicating the location of each and every register. */
--
2.40.1
^ permalink raw reply [flat|nested] 5+ messages in thread