1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
|
.. _implementation-defined-behavior:
===============================
Implementation-defined behavior
===============================
Contains the implementation details of the implementation-defined behavior in
libc++. Implementation-defined is mandated to be documented by the Standard.
.. note:
This page is far from complete.
Implementation-defined behavior
===============================
Updating the Time Zone Database
-------------------------------
The Standard allows implementations to automatically update the
*remote time zone database*. Libc++ opts not to do that. Instead calling
- ``std::chrono::remote_version()`` will update the version information of the
*remote time zone database*,
- ``std::chrono::reload_tzdb()``, if needed, will update the entire
*remote time zone database*.
This offers a way for users to update the *remote time zone database* and
give them full control over the process.
`[ostream.formatted.print]/3 <http://eel.is/c++draft/ostream.formatted.print#3>`_ A terminal capable of displaying Unicode
--------------------------------------------------------------------------------------------------------------------------
The Standard specifies that the manner in which a stream is determined to refer
to a terminal capable of displaying Unicode is implementation-defined. This is
used for ``std::print`` and similar functions taking an ``ostream&`` argument.
Libc++ determines that a stream is Unicode-capable terminal by:
* First it determines whether the stream's ``rdbuf()`` has an underlying
``FILE*``. This is ``true`` in the following cases:
* The stream is ``std::cout``, ``std::cerr``, or ``std::clog``.
* A ``std::basic_filebuf<CharT, Traits>`` derived from ``std::filebuf``.
* The way to determine whether this ``FILE*`` refers to a terminal capable of
displaying Unicode is the same as specified for `void vprint_unicode(FILE*
stream, string_view fmt, format_args args);
<http://eel.is/c++draft/print.fun#7>`_. This function is used for other
``std::print`` overloads that don't take an ``ostream&`` argument.
Listed in the index of implementation-defined behavior
======================================================
The order of the entries matches the entries in the
`draft of the Standard <http://eel.is/c++draft/impldefindex>`_.
|
