================
@@ -0,0 +1,66 @@
+.. title:: clang-tidy - bugprone-tagged-union-member-count
+
+bugprone-tagged-union-member-count
+==================================
+
+Gives warnings for tagged unions, where the number of tags is
+different from the number of data members inside the union.
+
+A struct or a class is considered to be a tagged union if it has
+exactly one union data member and exactly one enum data member and
+any number of other data members that are neither unions or enums.
+
+Example
+-------
+
+.. code-block:: c++
+
+ enum tags2 {
+ tag1,
+ tag2,
+ };
+
+ struct taggedunion { // warning: Tagged union has more data members than
tags! Data members: 3 Tags: 2 [bugprone-tagged-union-member-count]
+ enum tags2 kind;
+ union {
+ int i;
+ float f;
+ char *str;
+ } data;
+ };
+
+ enum tags4 {
+ tag1,
+ tag2,
+ tag3,
+ tag4,
+ };
+
+ struct taggedunion { // warning: Tagged union has more fewer members than
tags! Data members: 3 Tags: 4 [bugprone-tagged-union-member-count]
+ enum tags4 kind;
+ union {
+ int i;
+ float f;
+ char *str;
+ } data;
+ };
+
+Counting enum constant heuristic
+--------------------------------
+
+Some programmers use enums in such a way, where the value of the last enum
+constant is used to keep track of how many enum constants have been declared.
+
+.. code-block:: c++
+
+ enum tags_with_counter {
+ tag1, // is 0
+ tag2, // is 1
+ tag3, // is 2
+ tags_count, // is 3
+ };
+
+The checker detects this usage pattern heuristically and does not include
----------------
EugeneZelenko wrote:
```suggestion
The check detects this usage pattern heuristically and does not include
```
https://github.com/llvm/llvm-project/pull/89925
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