英文:
C++ {fmt} fmt::vformat with wide-string and fmt::make_wformat_args fails to compile
问题
此代码无法编译。(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;
}
然而,这段代码可以成功编译。
#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;
}
我正在使用 {fmt} 10.0.0 并包括 xchar.h,fmt::format
与宽字符串一起按预期工作,似乎只有 fmt::vformat
出现了问题。
我尝试过在不同配置下包含不同的独立 fmt 头文件(fmt/core.h,fmt/format.h,fmt/xchar.h)。这似乎毫无意义,因为 xchar.h 包含其他库的头文件。
虽然我专门使用 MSVC,但我尝试过并在 GCC 上遇到了相同的问题。
我尝试过使用 fmt::make_format_args
。
我还尝试过为 fmt::make_wformat_args
指定 fmt::wformat_context
模板参数。
我的具体用例要求我使用来自磁盘的本地化文件,因此我无法在编译时知道格式字符串。
英文:
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.
答案1
得分: 5
你不应该在自己没有编写格式化函数的情况下使用 fmt::vformat
。在运行时才知道的格式字符串的正确传递方式是将其包装在 fmt::runtime
中,并调用 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;
}
https://godbolt.org/z/4WKd575o7
英文:
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;
}
答案2
得分: 1
vformat
的第一个参数是一个字符串视图。似乎<fmt/xchar.h>
添加了一个重载,如下:
template<typename Char>
std::basic_string<Char> fmt::vformat(fmt::basic_string_view<Char>, basic_format_args<some_non_deduced_context>);
因此,Char
无法从 std::basic_string<wchar_t>
推断出来,你需要一个实际的 fmt::basic_string_view
:
std::wstring test = fmt::vformat(fmt::wstring_view(format), fmt::make_wformat_args(arg_1));
英文:
vformat
's first argument is a string view. Seems like <fmt/xchar.h>
adds an overload like:
template<typename Char>
std::basic_string<Char> fmt::vformat(fmt::basic_string_view<Char>, basic_format_args<some_non_deduced_context>);
So Char
can't be deduced from std::basic_string<wchar_t>
, and you need an actual fmt::basic_string_view
:
std::wstring test = fmt::vformat(fmt::wstring_view(format), fmt::make_wformat_args(arg_1));
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