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[clang-tidy] performance-unnecessary-copy-initialization: Create opti…
…on to exclude container types from triggering the check.
Add string list option of type names analagous to `AllowedTypes` which lets
users specify a list of ExcludedContainerTypes.
Types matching this list will not trigger the check when an expensive variable
is copy initialized from a const accessor method they provide, i.e.:
```
ExcludedContainerTypes = 'ExcludedType'
void foo() {
ExcludedType<ExpensiveToCopy> Container;
const ExpensiveToCopy NecessaryCopy = Container.get();
}
```
Even though an expensive to copy variable is copy initialized the check does not
trigger because the container type is excluded.
This is useful for container types that don't own their data, such as view types
where modification of the returned references in other places cannot be reliably
tracked, or const incorrect types.
Differential Revision: https://reviews.llvm.org/D106173
Reviewed-by: ymandel- Loading branch information
Felix Berger
committed
Jul 22, 2021
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60 changes: 60 additions & 0 deletions
60
...ng-tidy/checkers/performance-unnecessary-copy-initialization-excluded-container-types.cpp
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,60 @@ | ||
| // RUN: %check_clang_tidy %s performance-unnecessary-copy-initialization %t -- -config="{CheckOptions: [{key: performance-unnecessary-copy-initialization.ExcludedContainerTypes, value: 'ns::ViewType$;::ConstInCorrectType$'}]}" -- | ||
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| namespace ns { | ||
| template <typename T> | ||
| struct ViewType { | ||
| ViewType(const T &); | ||
| const T &view() const; | ||
| }; | ||
| } // namespace ns | ||
|
|
||
| template <typename T> | ||
| struct ViewType { | ||
| ViewType(const T &); | ||
| const T &view() const; | ||
| }; | ||
|
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||
| struct ExpensiveToCopy { | ||
| ~ExpensiveToCopy(); | ||
| void constMethod() const; | ||
| }; | ||
|
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| struct ConstInCorrectType { | ||
| const ExpensiveToCopy &secretlyMutates() const; | ||
| }; | ||
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| using NSVTE = ns::ViewType<ExpensiveToCopy>; | ||
| typedef ns::ViewType<ExpensiveToCopy> FewType; | ||
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| void positiveViewType() { | ||
| ExpensiveToCopy E; | ||
| ViewType<ExpensiveToCopy> V(E); | ||
| const auto O = V.view(); | ||
| // CHECK-MESSAGES: [[@LINE-1]]:14: warning: the const qualified variable 'O' is copy-constructed | ||
| // CHECK-FIXES: const auto& O = V.view(); | ||
| O.constMethod(); | ||
| } | ||
|
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| void excludedViewTypeInNamespace() { | ||
| ExpensiveToCopy E; | ||
| ns::ViewType<ExpensiveToCopy> V(E); | ||
| const auto O = V.view(); | ||
| O.constMethod(); | ||
| } | ||
|
|
||
| void excludedViewTypeAliased() { | ||
| ExpensiveToCopy E; | ||
| NSVTE V(E); | ||
| const auto O = V.view(); | ||
| O.constMethod(); | ||
|
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||
| FewType F(E); | ||
| const auto P = F.view(); | ||
| P.constMethod(); | ||
| } | ||
|
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| void excludedConstIncorrectType() { | ||
| ConstInCorrectType C; | ||
| const auto E = C.secretlyMutates(); | ||
| E.constMethod(); | ||
| } |