d3cfe19d7e
Co-authored-by: Marco Borgeaud <89914223+marco-antognini-sonarsource@users.noreply.github.com>
49 lines
1.7 KiB
Plaintext
49 lines
1.7 KiB
Plaintext
== Why is this an issue?
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The class `std::optional<T>` either stores a value of type `T` or is empty.
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One way to access the value of a non-empty optional is the ``++operator*++``. But using the dereference operator gives the optional appearance of a pointer when it is not: it models an object. Additionally, attempting to call the ``++operator*++`` on an empty optional will result in undefined behavior.
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Another way to access the value of a non-empty optional is the function `value()`. But assigning a value to the optional object through this function will throw an exception (`std::bad_optional_access`) if the optional has no value, and the assignment will not happen.
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For the assignment of an optional to happen correctly, whatever its state, it is better to:
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* assign the value directly with the `operator=`: e.g. `myOptionalInteger = 3;`
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* use the `emplace` function (for example, when the move or copy operation is expensive or forbidden).
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== How to fix it
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The rule raises an issue when the ``++operator*++`` or the `value()` function are used to assign a new value to an optional.
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=== Code examples
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==== Noncompliant code example
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[source,cpp,diff-id=1,diff-type=noncompliant]
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----
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void g(std::optional<int> &val, bool b) {
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if (b) {
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*val = 314; // Noncompliant; the behavior is undefined if the optional is empty.
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} else {
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val.value() = 42; // Noncompliant; it will throw if the optional is empty.
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}
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}
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----
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==== Compliant solution
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[source,cpp,diff-id=1,diff-type=compliant]
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----
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void g(std::optional<int> &val, bool b) {
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if (b) {
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val = 314; // Compliant
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} else {
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val = 42; // Compliant
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}
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}
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----
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== Resources
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* {cpp} reference - https://en.cppreference.com/w/cpp/utility/optional[std::optional]
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