1.. title:: clang-tidy - abseil-upgrade-duration-conversions
2
3abseil-upgrade-duration-conversions
4===================================
5
6Finds calls to ``absl::Duration`` arithmetic operators and factories whose
7argument needs an explicit cast to continue compiling after upcoming API
8changes.
9
10The operators ``*=``, ``/=``, ``*``, and ``/`` for ``absl::Duration`` currently
11accept an argument of class type that is convertible to an arithmetic type. Such
12a call currently converts the value to an ``int64_t``, even in a case such as
13``std::atomic<float>`` that would result in lossy conversion.
14
15Additionally, the ``absl::Duration`` factory functions (``absl::Hours``,
16``absl::Minutes``, etc) currently accept an ``int64_t`` or a floating-point
17type. Similar to the arithmetic operators, calls with an argument of class type
18that is convertible to an arithmetic type go through the ``int64_t`` path.
19
20These operators and factories will be changed to only accept arithmetic types to
21prevent unintended behavior. After these changes are released, passing an
22argument of class type will no longer compile, even if the type is implicitly
23convertible to an arithmetic type.
24
25Here are example fixes created by this check:
26
27.. code-block:: c++
28
29  std::atomic<int> a;
30  absl::Duration d = absl::Milliseconds(a);
31  d *= a;
32
33becomes
34
35.. code-block:: c++
36
37  std::atomic<int> a;
38  absl::Duration d = absl::Milliseconds(static_cast<int64_t>(a));
39  d *= static_cast<int64_t>(a);
40
41Note that this check always adds a cast to ``int64_t`` in order to preserve the
42current behavior of user code. It is possible that this uncovers unintended
43behavior due to types implicitly convertible to a floating-point type.
44