59 lines
1.7 KiB
ReStructuredText
59 lines
1.7 KiB
ReStructuredText
.. title:: clang-tidy - performance-avoid-endl
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performance-avoid-endl
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============================
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Checks for uses of ``std::endl`` on streams and suggests using the newline
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character ``'\n'`` instead.
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Rationale:
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Using ``std::endl`` on streams can be less efficient than using the newline
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character ``'\n'`` because ``std::endl`` performs two operations: it writes a
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newline character to the output stream and then flushes the stream buffer.
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Writing a single newline character using ``'\n'`` does not trigger a flush,
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which can improve performance. In addition, flushing the stream buffer can
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cause additional overhead when working with streams that are buffered.
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Example:
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Consider the following code:
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.. code-block:: c++
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#include <iostream>
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int main() {
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std::cout << "Hello" << std::endl;
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}
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Which gets transformed into:
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.. code-block:: c++
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#include <iostream>
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int main() {
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std::cout << "Hello" << '\n';
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}
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This code writes a single newline character to the ``std::cout`` stream without
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flushing the stream buffer.
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Additionally, it is important to note that the standard C++ streams (like
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``std::cerr``, ``std::wcerr``, ``std::clog`` and ``std::wclog``)
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always flush after a write operation, unless ``std::ios_base::sync_with_stdio``
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is set to ``false``. regardless of whether ``std::endl`` or ``'\n'`` is used.
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Therefore, using ``'\n'`` with these streams will not
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result in any performance gain, but it is still recommended to use
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``'\n'`` for consistency and readability.
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If you do need to flush the stream buffer, you can use ``std::flush``
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explicitly like this:
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.. code-block:: c++
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#include <iostream>
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int main() {
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std::cout << "Hello\n" << std::flush;
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}
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