168ade72f8
in in {fmt} before v10, it provides the specialization of `fmt::formatter<..>`
for `std::string_view` as well as the specialization of `fmt::formatter<..>`
for `fmt::string_view` which is an implementation builtin in {fmt} for
compatibility of pre-C++17. and this type is used even if the code is
compiled with C++ stadandard greater or equal to C++17. also, before v10,
the `fmt::formatter<std::string_view>::format()` is defined so it accepts
`std::string_view`. after v10, `fmt::formatter<std::string_view>` still
exists, but it is now defined using `format_as()` machinery, so it's
`format()` method does not actually accept `std::string_view`, it
accepts `fmt::string_view`, as the former can be converted to
`fmt::string_view`.
this is why we can inherit from `fmt::formatter<std::string_view>` and
use `formatter<std::string_view>::format(foo, ctx);` to implement the
`format()` method with {fmt} v9, but we cannot do this with {fmt} v10,
and we would have following compilation failure:
```
FAILED: service/CMakeFiles/service.dir/RelWithDebInfo/topology_state_machine.cc.o
/home/kefu/.local/bin/clang++ -DFMT_DEPRECATED_OSTREAM -DFMT_SHARED -DSCYLLA_BUILD_MODE=release -DSEASTAR_API_LEVEL=7 -DSEASTAR_LOGGER_COMPILE_TIME_FMT -DSEASTAR_LOGGER_TYPE_STDOUT -DSEASTAR_SCHEDULING_GROUPS_COUNT=16 -DSEASTAR_SSTRING -DXXH_PRIVATE_API -DCMAKE_INTDIR=\"RelWithDebInfo\" -I/home/kefu/dev/scylladb -I/home/kefu/dev/scylladb/build/gen -I/home/kefu/dev/scylladb/seastar/include -I/home/kefu/dev/scylladb/build/seastar/gen/include -I/home/kefu/dev/scylladb/build/seastar/gen/src -ffunction-sections -fdata-sections -O3 -g -gz -std=gnu++20 -fvisibility=hidden -Wall -Werror -Wextra -Wno-error=deprecated-declarations -Wimplicit-fallthrough -Wno-c++11-narrowing -Wno-deprecated-copy -Wno-mismatched-tags -Wno-missing-field-initializers -Wno-overloaded-virtual -Wno-unsupported-friend -Wno-enum-constexpr-conversion -Wno-unused-parameter -ffile-prefix-map=/home/kefu/dev/scylladb=. -march=westmere -mllvm -inline-threshold=2500 -fno-slp-vectorize -U_FORTIFY_SOURCE -Werror=unused-result -MD -MT service/CMakeFiles/service.dir/RelWithDebInfo/topology_state_machine.cc.o -MF service/CMakeFiles/service.dir/RelWithDebInfo/topology_state_machine.cc.o.d -o service/CMakeFiles/service.dir/RelWithDebInfo/topology_state_machine.cc.o -c /home/kefu/dev/scylladb/service/topology_state_machine.cc
/home/kefu/dev/scylladb/service/topology_state_machine.cc:254:41: error: no matching member function for call to 'format'
254 | return formatter<std::string_view>::format(it->second, ctx);
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~
/usr/include/fmt/core.h:2759:22: note: candidate function template not viable: no known conversion from 'seastar::basic_sstring<char, unsigned int, 15>' to 'const fmt::basic_string_view<char>' for 1st argument
2759 | FMT_CONSTEXPR auto format(const T& val, FormatContext& ctx) const
| ^ ~~~~~~~~~~~~
```
because the inherited `format()` method actually comes from
`fmt::formatter<fmt::string_view>`. to reduce the confusion, in this
change, we just inherit from `fmt::format<string_view>`, where
`string_view` is actually `fmt::string_view`. this follows
the document at
https://fmt.dev/latest/api.html#formatting-user-defined-types,
and since there is less indirection under the hood -- we do not
use the specialization created by `FMT_FORMAT_AS` which inherit
from `formatter<fmt::string_view>`, hopefully this can improve
the compilation speed a little bit. also, this change addresses
the build failure with {fmt} v10.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closes scylladb/scylladb#18299
90 lines
2.9 KiB
C++
90 lines
2.9 KiB
C++
/*
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* Copyright (C) 2017-present ScyllaDB
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*/
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/*
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* SPDX-License-Identifier: AGPL-3.0-or-later
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*/
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#pragma once
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#include <type_traits>
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#include <seastar/core/sstring.hh>
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#include <seastar/core/enum.hh>
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namespace sstables {
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enum class sstable_version_types { ka, la, mc, md, me };
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enum class sstable_format_types { big };
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constexpr std::array<sstable_version_types, 5> all_sstable_versions = {
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sstable_version_types::ka,
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sstable_version_types::la,
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sstable_version_types::mc,
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sstable_version_types::md,
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sstable_version_types::me,
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};
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constexpr std::array<sstable_version_types, 3> writable_sstable_versions = {
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sstable_version_types::mc,
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sstable_version_types::md,
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sstable_version_types::me,
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};
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constexpr sstable_version_types oldest_writable_sstable_format = sstable_version_types::mc;
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template <size_t S1, size_t S2>
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constexpr bool check_sstable_versions(const std::array<sstable_version_types, S1>& all_sstable_versions,
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const std::array<sstable_version_types, S2>& writable_sstable_versions, sstable_version_types oldest_writable_sstable_format) {
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for (auto v : writable_sstable_versions) {
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if (v < oldest_writable_sstable_format) {
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return false;
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}
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}
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size_t expected = 0;
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for (auto v : all_sstable_versions) {
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if (v >= oldest_writable_sstable_format) {
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++expected;
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}
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}
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return expected == S2;
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}
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static_assert(check_sstable_versions(all_sstable_versions, writable_sstable_versions, oldest_writable_sstable_format));
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inline auto get_highest_sstable_version() {
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return all_sstable_versions[all_sstable_versions.size() - 1];
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}
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sstable_version_types version_from_string(std::string_view s);
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sstable_format_types format_from_string(std::string_view s);
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extern const std::unordered_map<sstable_version_types, seastar::sstring, seastar::enum_hash<sstable_version_types>> version_string;
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extern const std::unordered_map<sstable_format_types, seastar::sstring, seastar::enum_hash<sstable_format_types>> format_string;
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inline int operator<=>(sstable_version_types a, sstable_version_types b) {
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auto to_int = [] (sstable_version_types x) {
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return static_cast<std::underlying_type_t<sstable_version_types>>(x);
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};
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return to_int(a) - to_int(b);
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}
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}
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template <>
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struct fmt::formatter<sstables::sstable_version_types> : fmt::formatter<string_view> {
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template <typename FormatContext>
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auto format(const sstables::sstable_version_types& version, FormatContext& ctx) const {
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return fmt::format_to(ctx.out(), "{}", sstables::version_string.at(version));
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}
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};
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template <>
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struct fmt::formatter<sstables::sstable_format_types> : fmt::formatter<string_view> {
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template <typename FormatContext>
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auto format(const sstables::sstable_format_types& format, FormatContext& ctx) const {
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return fmt::format_to(ctx.out(), "{}", sstables::format_string.at(format));
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}
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};
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