facebook
remove_const from value_type of Range::value_type
in general, value_type in a range-alike type should not be qualified with const specifier. the reference type does.
before this change, when formatting StringPiece, fmt 11 does not consider it as a formattable type, as it falls into the string-alike category, but its value_type is const char which is different from the Char type of the context, which is char when formatting using fmt::format("{}", ipSlashCidr).
hence we have the build failure like:
/usr/include/fmt/base.h: In instantiation of ‘constexpr fmt::v11::detail::value<Context> fmt::v11::detail::make_arg(T&) [with bool PACKED = true; Context = fmt::v11::context; T = folly::Range<const char*>; typename std::enable_if<PACKED, int>::type <anonymous> = 0]’:
/usr/include/fmt/base.h:2002:74: required from ‘constexpr fmt::v11::detail::format_arg_store<Context, NUM_ARGS, 0, DESC> fmt::v11::make_format_args(T& ...) [with Context = context; T = {folly::Range<const char*>}; long unsigned int NUM_ARGS = 1; long unsigned int NUM_NAMED_ARGS = 0; long long unsigned int DESC = 15; typename std::enable_if<(NUM_NAMED_ARGS == 0), int>::type <anonymous> = 0]’
2002 | return {{detail::make_arg<NUM_ARGS <= detail::max_packed_args, Context>(
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
2003 | args)...}};
| ~~~~~
/usr/include/fmt/format.h:4357:44: required from ‘std::string fmt::v11::format(format_string<T ...>, T&& ...) [with T = {folly::Range<const char*>&}; std::string = std::__cxx11::basic_string<char>; format_string<T ...> = basic_format_string<char, folly::Range<const char*>&>]’
4357 | return vformat(fmt, fmt::make_format_args(args...));
| ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~
/home/kefu/folly/folly/IPAddress.cpp:100:47: required from here
100 | throw IPAddressFormatException(fmt::format(
| ~~~~~~~~~~~^
101 | "Invalid ipSlashCidr specified. Expected IP/CIDR format, got '{}'",
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
102 | ipSlashCidr));
| ~~~~~~~~~~~~
/usr/include/fmt/base.h:1611:17: error: static assertion failed: Mixing character types is disallowed.
1611 | static_assert(formattable_char, "Mixing character types is disallowed.");
| ^~~~~~~~~~~~~~~~
/usr/include/fmt/base.h:1611:17: note: ‘formattable_char’ evaluates to false
/usr/include/fmt/base.h: In instantiation of ‘constexpr fmt::v11::detail::value<Context> fmt::v11::detail::make_arg(T&) [with bool PACKED = true; Context = fmt::v11::context; T = const folly::Range<const char*>; typename std::enable_if<PACKED, int>::type <anonymous> = 0]’:
/usr/include/fmt/base.h:2002:74: required from ‘constexpr fmt::v11::detail::format_arg_store<Context, NUM_ARGS, 0, DESC> fmt::v11::make_format_args(T& ...) [with Context = context; T = {const folly::Range<const char*>}; long unsigned int NUM_ARGS = 1; long unsigned int NUM_NAMED_ARGS = 0; long long unsigned int DESC = 15; typename std::enable_if<(NUM_NAMED_ARGS == 0), int>::type <anonymous> = 0]’
2002 | return {{detail::make_arg<NUM_ARGS <= detail::max_packed_args, Context>(
| ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^
2003 | args)...}};
| ~~~~~
/usr/include/fmt/format.h:4357:44: required from ‘std::string fmt::v11::format(format_string<T ...>, T&& ...) [with T = {const folly::Range<const char*>&}; std::string = std::__cxx11::basic_string<char>; format_string<T ...> = basic_format_string<char, const folly::Range<const char*>&>]’
4357 | return vformat(fmt, fmt::make_format_args(args...));
| ~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~
/home/kefu/folly/folly/IPAddress.cpp:113:22: required from here
113 | fmt::format("Invalid IP address {}", vec.at(0)));
| ~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
/usr/include/fmt/base.h:1611:17: error: static assertion failed: Mixing character types is disallowed.
1611 | static_assert(formattable_char, "Mixing character types is disallowed.");
| ^~~~~~~~~~~~~~~~
/usr/include/fmt/base.h:1611:17: note: ‘formattable_char’ evaluates to false
in this change, we use the non-const value type, and update the some methods where the reference type is supposed to be used.
Fixes #2172 Signed-off-by: Kefu Chai [email protected]
@Orvid has imported this pull request. If you are a Meta employee, you can view this diff on Phabricator.
Looks like we're going with https://github.com/facebook/folly/pull/2265 instead
@michel-slm thanks, i still think the std::iterator_traits<Iter>::value_type is a better solution. but please feel free to close this one once #2265 lands.
Superseded by https://github.com/facebook/folly/commit/21e8dcd464ee46b2144a1e4d4c0e452355ae15f0 but thanks anyway.
