64 lines
1.9 KiB
ReStructuredText
64 lines
1.9 KiB
ReStructuredText
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.. title:: clang-tidy - bugprone-stringview-nullptr
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bugprone-stringview-nullptr
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===========================
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Checks for various ways that the ``const CharT*`` constructor of
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``std::basic_string_view`` can be passed a null argument and replaces them
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with the default constructor in most cases. For the comparison operators,
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braced initializer list does not compile so instead a call to ``.empty()``
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or the empty string literal are used, where appropriate.
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This prevents code from invoking behavior which is unconditionally undefined.
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The single-argument ``const CharT*`` constructor does not check for the null
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case before dereferencing its input. The standard is slated to add an
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explicitly-deleted overload to catch some of these cases: wg21.link/p2166
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To catch the additional cases of ``NULL`` (which expands to ``__null``) and
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``0``, first run the ``modernize-use-nullptr`` check to convert the callers to
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``nullptr``.
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.. code-block:: c++
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std::string_view sv = nullptr;
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sv = nullptr;
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bool is_empty = sv == nullptr;
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bool isnt_empty = sv != nullptr;
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accepts_sv(nullptr);
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accepts_sv({{}}); // A
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accepts_sv({nullptr, 0}); // B
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is translated into...
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.. code-block:: c++
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std::string_view sv = {};
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sv = {};
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bool is_empty = sv.empty();
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bool isnt_empty = !sv.empty();
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accepts_sv("");
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accepts_sv(""); // A
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accepts_sv({nullptr, 0}); // B
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.. note::
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The source pattern with trailing comment "A" selects the ``(const CharT*)``
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constructor overload and then value-initializes the pointer, causing a null
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dereference. It happens to not include the ``nullptr`` literal, but it is
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still within the scope of this ClangTidy check.
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.. note::
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The source pattern with trailing comment "B" selects the
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``(const CharT*, size_type)`` constructor which is perfectly valid, since the
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length argument is ``0``. It is not changed by this ClangTidy check.
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