https://gcc.gnu.org/onlinedocs/gcc/C_002b_002b-Dialect-Options.html#index-fno-pretty-templates
The gcc option -fno-pretty-templates changes the __PRETTY_FUNCTION__ from e.g.
"auto n() [with E = E]" to "auto n<E>()" (more like MSVC).
Pass the entire __PRETTY_FUNCTION__ / __FUNCSIG__ to pretty_name(), and truncate it there, checking the last character if necessary to determine the format used.
This is necessary to avoid compilation errors using recent libc++
versions with C++23 due to libc++ taking steps to remove transitive
includes in newer C++ versions [0].
For a more concrete example, this program builds using Clang 16.0.0 and
C++20, but fails to build with C++23:
#include <magic_enum.hpp>
enum class ec { RED };
template <>
constexpr auto magic_enum::customize::enum_name(ec val) noexcept
-> magic_enum::customize::customize_t {
switch (val) {
case ec::RED: return "Red";
};
return invalid_tag;
}
The compiler hits the "too many errors" threshold when building with
C++23, but I believe this is due to compiling failing to recover after
the first error. The error message starts with:
include % /usr/local/opt/llvm/bin/clang++ -std=c++2b -c test.cpp
In file included from test.cpp:1:
./magic_enum.hpp:324:61: error: no member named 'equal_to' in namespace 'std'
return std::is_same_v<std::decay_t<BinaryPredicate>, std::equal_to<string_view::value_type>> ||
~~~~~^
./magic_enum.hpp:324:93: error: expected '(' for function-style cast or type construction
return std::is_same_v<std::decay_t<BinaryPredicate>, std::equal_to<string_view::value_type>> ||
~~~~~~~~~~~~~~~~~~~~~~~^
./magic_enum.hpp:324:96: error: expected expression
return std::is_same_v<std::decay_t<BinaryPredicate>, std::equal_to<string_view::value_type>> ||
^
std::equal_to is defined in <functional>, but <functional> is not
directly included by magic_enum.hpp. <string> [1] and <string_view> [2]
both include <functional> for C++20 and earlier, but they no longer
include <functional> in C++23 and later, so a definition for
std::equal_to is no longer visible, leading to the above error.
Directly including <functional> fixes this error, but I'm not sure there
aren't similar errors.
[0]: 8ff2d6af69
[1]: https://github.com/llvm/llvm-project/blob/llvmorg-16.0.0/libcxx/include/string#L4625
[2]: https://github.com/llvm/llvm-project/blob/llvmorg-16.0.0/libcxx/include/string_view#L1027
Co-authored-by: Alex Wang <ts826848@gmail.com>
