llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-temporal-safety
Author: Utkarsh Saxena (usx95)
<details>
<summary>Changes</summary>
```cpp
// This pattern was previously flagged as a lifetime violation
for (auto it = my_map.begin(); it != my_map.end(); ) {
if (should_delete(*it)) {
my_map.erase(it++); // Safe in map, but flagged as invalidating 'it'
} else {
++it;
}
}
```
---
Full diff: https://github.com/llvm/llvm-project/pull/181216.diff
3 Files Affected:
- (modified) clang/lib/Analysis/LifetimeSafety/LifetimeAnnotations.cpp (+24-2)
- (modified) clang/test/Sema/Inputs/lifetime-analysis.h (+1)
- (modified) clang/test/Sema/warn-lifetime-safety-invalidations.cpp (+15)
``````````diff
diff --git a/clang/lib/Analysis/LifetimeSafety/LifetimeAnnotations.cpp
b/clang/lib/Analysis/LifetimeSafety/LifetimeAnnotations.cpp
index 01666f4ac271c..67d06f17ffd74 100644
--- a/clang/lib/Analysis/LifetimeSafety/LifetimeAnnotations.cpp
+++ b/clang/lib/Analysis/LifetimeSafety/LifetimeAnnotations.cpp
@@ -317,12 +317,33 @@ bool isContainerInvalidationMethod(const CXXMethodDecl
&MD) {
if (!MD.getIdentifier())
return false;
+
+ StringRef MethodName = MD.getName();
+
+ // Special handling for 'erase':
+ // It invalidates the whole container (effectively) for contiguous/flat
+ // storage, but is safe for other iterators in node-based containers.
+ if (MethodName == "erase") {
+ static const llvm::StringSet<> NodeBasedContainers = {"map",
+ "set",
+ "multimap",
+ "multiset",
+ "unordered_map",
+ "unordered_set",
+ "unordered_multimap",
+
"unordered_multiset"};
+
+ // 'erase' invalidates for non node-based containers (vector, deque,
string,
+ // flat_map).
+ return !NodeBasedContainers.contains(ContainerName);
+ }
+
static const llvm::StringSet<> InvalidatingMembers = {
// Basic Insertion/Emplacement
"push_front", "push_back", "emplace_front", "emplace_back", "insert",
"emplace", "push",
// Basic Removal/Clearing
- "pop_front", "pop_back", "pop", "erase", "clear",
+ "pop_front", "pop_back", "pop", "clear",
// Memory Management
"reserve", "resize", "shrink_to_fit",
// Assignment (Named)
@@ -331,6 +352,7 @@ bool isContainerInvalidationMethod(const CXXMethodDecl &MD)
{
"append", "replace",
// Modern C++ (C++17/23)
"extract", "try_emplace", "insert_range", "append_range",
"assign_range"};
- return InvalidatingMembers.contains(MD.getName());
+
+ return InvalidatingMembers.contains(MethodName);
}
} // namespace clang::lifetimes
diff --git a/clang/test/Sema/Inputs/lifetime-analysis.h
b/clang/test/Sema/Inputs/lifetime-analysis.h
index f1c84ff0a3f68..a5b6d1c34d82f 100644
--- a/clang/test/Sema/Inputs/lifetime-analysis.h
+++ b/clang/test/Sema/Inputs/lifetime-analysis.h
@@ -90,6 +90,7 @@ struct unordered_map {
T& operator[](const Key& key);
iterator begin();
iterator end();
+ iterator erase(iterator);
};
template<typename T>
diff --git a/clang/test/Sema/warn-lifetime-safety-invalidations.cpp
b/clang/test/Sema/warn-lifetime-safety-invalidations.cpp
index d90c952e26e5d..d23894e68fcb0 100644
--- a/clang/test/Sema/warn-lifetime-safety-invalidations.cpp
+++ b/clang/test/Sema/warn-lifetime-safety-invalidations.cpp
@@ -148,6 +148,21 @@ void IteratorInvalidationInAWhileLoop(std::vector<int> v) {
}
}
+void NoIteratorInvalidationInAWhileLoopErase(std::unordered_map<int, int> mp) {
+ auto it = mp.begin();
+ while (it != std::end(mp)) {
+ if (Bool()) {
+ auto next = it;
+ ++next;
+ mp.erase(it); // Ok. 'next' remains valid.
+ it = next;
+ }
+ else {
+ ++it;
+ }
+ }
+}
+
void IteratorInvalidationInAForeachLoop(std::vector<int> v) {
for (int& x : v) { // expected-warning {{object whose reference is captured
is later invalidated}} \
// expected-note {{later used here}}
``````````
</details>
https://github.com/llvm/llvm-project/pull/181216
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