enum_flags to_string (was: Re: [PATCH v2 07/29] Thread options & clone events (core + remote))
Commit Message
Hi,
On 2022-07-21 4:14 a.m., Simon Marchi wrote:
>> + ptid = ptid_t (ptid.pid ());
>> +
>> + for_each_thread ([&] (thread_info *thread)
>> + {
>> + if (ptid_of (thread).matches (ptid))
>> + set_options[thread] = options;
>> + });
>> + }
>> +
>> + for (const auto &iter : set_options)
>> + {
>> + thread_info *thread = iter.first;
>> + gdb_thread_options options = iter.second;
>> +
>> + if (debug_threads && thread->thread_options != options)
>> + {
>> + debug_printf ("[options for %s are now 0x%x]\n",
>> + target_pid_to_str (ptid_of (thread)).c_str (),
>> + (unsigned) options);
>
> This should probably use threads_debug_printf.
>
> IWBN to have a small function that formats `options` as an "or" of the
> enabled bits, it would make logs easier to read. For example if the two
> options are enabled, it would show up as "GDB_TO_CLONE | GDB_TO_EXIT".
>
How about this? Since I think we'd want to print every enum_flags type
using the same format, I wrote code that can be used by all enum_flags
specializations to convert to string. Each specialization just needs to
provide the enumerator->string mapping, since there's no reflection
in C++ (yet).
From 6ed71a904b84b95ced85e8dda496ce79a5f205b4 Mon Sep 17 00:00:00 2001
From: Pedro Alves <pedro@palves.net>
Date: Tue, 25 Oct 2022 15:39:37 +0100
Subject: [PATCH] enum_flags to_string
This commit introduces shared infrastructure that can be used to
implement enum_flags -> to_string functions. With this, if we want to
support converting a given enum_flags specialization to string, we
just need to implement a function that provides the enumerator->string
mapping, like so:
enum some_flag
{
SOME_FLAG1 = 1 << 1,
SOME_FLAG2 = 1 << 2,
SOME_FLAG3 = 1 << 3,
};
DEF_ENUM_FLAGS_TYPE (some_flag, some_flags);
static std::string
to_string (some_flags flags)
{
#define CASE(X) { X, #X }
static constexpr test_flags::string_map_element mapping[] = {
CASE (SOME_FLAG1),
CASE (SOME_FLAG2),
CASE (SOME_FLAG3),
};
#undef CASE
return flags.to_string (mapping);
}
.. and then to_string(SOME_FLAG1 | SOME_FLAG2) produces a string like
"0x6 [SOME_FLAG1 SOME_FLAG2]".
If we happen to forget to update the mapping array when we introduce a
new enumerator, then the string representation will pretty-print the
flags it knows about, and then the leftover flags in hex (one single
number). For example, if we had missed mapping SOME_FLAG2 above, we'd
end up with:
to_string(SOME_FLAG1 | SOME_FLAG2) => "0x6 [SOME_FLAG1 0x4]");
Other than in the unit tests included, no actual usage of the
functionality is added in this commit.
Change-Id: I835de43c33d13bc0c95132f42c3f97318b875779
---
gdb/unittests/enum-flags-selftests.c | 27 ++++++++++++++
gdbsupport/enum-flags.h | 53 ++++++++++++++++++++++++++++
2 files changed, 80 insertions(+)
base-commit: 508ccf9b3e1db355037a4a1c9004efe0d6d3ffbf
@@ -374,6 +374,23 @@ enum test_uflag : unsigned
DEF_ENUM_FLAGS_TYPE (test_flag, test_flags);
DEF_ENUM_FLAGS_TYPE (test_uflag, test_uflags);
+/* to_string enumerator->string mapping function used to test
+ enum_flags::to_string. This intentionally misses mapping one
+ enumerator (FLAG2). */
+
+static std::string
+to_string (test_flags flags)
+{
+#define CASE(X) { X, #X }
+ static constexpr test_flags::string_map_element mapping[] = {
+ CASE (FLAG1),
+ CASE (FLAG3),
+ };
+#undef CASE
+
+ return flags.to_string (mapping);
+}
+
static void
self_test ()
{
@@ -581,6 +598,16 @@ self_test ()
SELF_CHECK (ok);
}
+
+ /* Check string conversion. */
+ {
+ SELF_CHECK (to_string (0) == "0x0 []");
+ SELF_CHECK (to_string (FLAG1) == "0x2 [FLAG1]");
+ SELF_CHECK (to_string (FLAG1 | FLAG3) == "0xa [FLAG1 FLAG3]");
+ SELF_CHECK (to_string (FLAG1 | FLAG2 | FLAG3) == "0xe [FLAG1 FLAG3 0x4]");
+ SELF_CHECK (to_string (FLAG2) == "0x4 [0x4]");
+ SELF_CHECK (to_string (test_flag (0xff)) == "0xff [FLAG1 FLAG3 0xf5]");
+ }
}
} /* namespace enum_flags_tests */
@@ -130,6 +130,13 @@ class enum_flags
typedef E enum_type;
typedef typename enum_underlying_type<enum_type>::type underlying_type;
+ /* For to_string. Maps one enumerator of E to a string. */
+ struct string_map_element
+ {
+ E flag;
+ const char *str;
+ };
+
public:
/* Allow default construction. */
constexpr enum_flags ()
@@ -183,6 +190,52 @@ class enum_flags
/* Binary operations involving some unrelated type (which would be a
bug) are implemented as non-members, and deleted. */
+ /* Convert this object to a std::string, using MAPPING as
+ enumerator-to-string mapping array. This is not meant to be
+ called directly. Instead, enum_flags specializations that have
+ their own to_string function wrapping this one, thus hidding the
+ mapping array from callers. */
+
+ template<size_t N>
+ std::string
+ to_string (const string_map_element (&mapping)[N]) const
+ {
+ enum_type flags = raw ();
+ std::string res = hex_string (flags);
+ res += " [";
+
+ bool need_space = false;
+ for (const auto &entry : mapping)
+ {
+ if ((flags & entry.flag) != 0)
+ {
+ /* Do op~ in the underlying type, because if enum_type's
+ underlying type is signed, op~ won't be defined for
+ it. */
+ flags &= (enum_type) ~(underlying_type) entry.flag;
+
+ if (need_space)
+ res += " ";
+ res += entry.str;
+
+ need_space = true;
+ }
+ }
+
+ /* If there were flags not included in the mapping, print them as
+ an hex number. */
+ if (flags != 0)
+ {
+ if (need_space)
+ res += " ";
+ res += hex_string (flags);
+ }
+
+ res += "]";
+
+ return res;
+ }
+
private:
/* Stored as enum_type because GDB knows to print the bit flags
neatly if the enum values look like bit flags. */