How to make char16_t acceptable as a template parameter to basic_ifstream?

Asked Aug 09 '20 at 00:02

Active Aug 09 '20 at 00:38

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I am using C++17 on macOS and char16_t is not acceptable as a template parameter as follow:

basic_ifstream<char16_t> file("c:\\file.txt", ios_base::ate);
streamsize size = file.tellg();
file.seekg(0, ios_base::beg);
u16string str(size/2, 0);
file.read(reinterpret_cast<char16_t*>(&str[0]), size);
file.close();

The previous code is working on windows but it doesn't work on macOS.

Also, there are indirect error implicit instantiation of undefined template std::__1::ctype<char16_t> appears in "istream.h", "__locale.h" and when change char16_t to something else that error disappear.

Is there a solution to that problem or it's like the other poor things that in c++?

edited Aug 09 '20 at 00:38

asked Aug 09 '20 at 00:02

Lion King

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A C++ implementation may provide a specialization for `char16_t`, but is not required to do so. If a particular C++ implementation does not provide a `char16_t` specialization, that's pretty much the end of the story. – Sam Varshavchik Aug 09 '20 at 00:04
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It what way does it not work? – jkb Aug 09 '20 at 00:06
Can you declare the type yourself in a common header in your project? `typedef uint16_t char16_t` – Seth Aug 09 '20 at 00:17
@jkb: I don't understand what do you mean? – Lion King Aug 09 '20 at 00:30
1

Are you getting a compiler error, or does it not behave properly at runtime? Add details so we understand what isn't working when you say "doesn't work". – 1201ProgramAlarm Aug 09 '20 at 00:31
@1201ProgramAlarm: I have updated my question and added something about that point. – Lion King Aug 09 '20 at 00:41

How to make char16_t acceptable as a template parameter to basic_ifstream?

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