================
@@ -0,0 +1,48 @@
+.. title:: clang-tidy - bugprone-loop-variable-copied-then-modified
+
+bugprone-loop-variable-copied-then-modified
+===========================================
+
+Detects when a loop variable is copied and then subsequently (possibly)
modified
+and suggests replacing with a reference or an explicit copy.
+
+This pattern is considered bugprone because, frequently, programmers do not
+realize that they are modifying a *copy* rather than an underlying value,
+resulting in subtly erroneous code.
+
+For instance, the following code attempts to null out a value in a map, but
only
+succeeds in nulling out a value in a *copy* of the map:
+
+.. code-block:: c++
+
+ for (auto target : target_map) {
+ target.value = nullptr;
+ }
+
+The programmer is likely to have intended this code instead:
+
+.. code-block:: c++
+
+ for (auto& target : target_map) {
+ target.value = nullptr;
+ }
+
+This code can be fixed in one of two ways:
+ - In cases where the programmer did not intend to create a copy, they can
+ convert the loop variable to a reference or a ``const`` reference. A fix-it
+ message will provide a naive suggestion of how to achieve this, which works
+ in most cases.
+ - In cases where the intent is in fact to modify a copy, they may perform the
+ copy explicitly, inside the body of the loop, and perform whatever
+ operations they like on that copy.
+
+This is a conservative check: in cases where it cannot be determined at compile
+time whether or not a particular function modifies the variable, it assumes a
+modification has ocurred and warns accordingly. However, in such cases, the
+warning can still be suppressed by doing one of the actions described above.
+
+.. option:: IgnoreInexpensiveVariables
----------------
EugeneZelenko wrote:
```suggestion
Options
-------
.. option:: IgnoreInexpensiveVariables
```
https://github.com/llvm/llvm-project/pull/157213
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