This code fails to compile. (error: no matching function for call to 'vformat(std::wstring&, fmt::v10::format_arg_store<fmt::v10::basic_format_context<std::back_insert_iterator<fmt::v10::detail::buffer<wchar_t> >, wchar_t>, int>)')
#include <fmt/xchar.h>
#include <string>
#include <iostream>
int main() {
int arg_1 = 12;
std::wstring format = L"Hello {}";
std::wstring test = fmt::vformat(format, fmt::make_wformat_args(arg_1));
std::wcout << test;
return 0;
}
However, this code successfully compiles.
#include <fmt/xchar.h>
#include <string>
#include <iostream>
int main() {
int arg_1 = 12;
std::string format = "Hello {}";
std::string test = fmt::vformat(format, fmt::make_format_args(arg_1));
std::cout << test;
return 0;
}
I am using {fmt} 10.0.0 and including xchar.h, fmt::format works as I would expect with wide strings, it seems I am facing this problem with only fmt::vformat.
I have tried including various separate fmt header files in different configurations (fmt/core.h, fmt/format.h, fmt/xchar.h). This seems pointless as xchar.h includes the other libraries header files.
While I specifically use MSVC, I have tried and have had the same issue on GCC.
I have tried using fmt::make_format_args instead.
I have also tried specifying the fmt::wformat_context template parameter for fmt::make_wformat_args.
My specific use case has me using localization files from disk, so I cannot know the format strings at compile time.
You shouldn't be using fmt::vformat except when writing a formatting function yourself. A proper way to pass a format string only known at runtime is by wrapping it in fmt::runtime and calling fmt::format:
#include <fmt/xchar.h>
#include <iostream>
int main() {
int arg_1 = 12;
std::wstring format = L"Hello {}";
std::wstring test = fmt::format(fmt::runtime(format), arg_1);
std::wcout << test;
}