llvmbot wrote:
<!--LLVM PR SUMMARY COMMENT-->
@llvm/pr-subscribers-clang-analysis
@llvm/pr-subscribers-clang-temporal-safety
Author: Utkarsh Saxena (usx95)
<details>
<summary>Changes</summary>
Fix lifetime tracking for pointer-like methods on non-owner types
Modified the `shouldTrackImplicitObjectArg` function to only track pointer-like
return types when the function object parameter is a GSL owner type. This
prevents incorrectly tracking methods on view types like
`std::string_view::begin()`.
Also updated a test case to remove an expected warning that is no longer
applicable, and added a comment explaining why we can't catch certain bugs with
view type accessors.
The current implementation was incorrectly tracking pointer-like return types
for all GSL pointer types, including view types. This change makes the tracking
more precise by only tracking pointer-like return types when the function
object parameter is a GSL owner type, which better aligns with the intended
behavior of the lifetime safety analysis.
This resolves false-positives like
```cpp
const char* p;
{
std::string_view a = getSomeView();
p = a.data(); // 'a' does not live long enough (false-positive).
}
use(p);
```
This also introduces a false-negative in the pre-existing analysis which
special cased this
```cpp
const char *trackThroughMultiplePointer() {
return
std::basic_string_view<char>(std::basic_string<char>()).begin();
}
```
---
Full diff: https://github.com/llvm/llvm-project/pull/174741.diff
2 Files Affected:
- (modified) clang/lib/Analysis/LifetimeSafety/LifetimeAnnotations.cpp (+2-1)
- (modified) clang/test/Sema/warn-lifetime-analysis-nocfg.cpp (+3-1)
``````````diff
diff --git a/clang/lib/Analysis/LifetimeSafety/LifetimeAnnotations.cpp
b/clang/lib/Analysis/LifetimeSafety/LifetimeAnnotations.cpp
index 2772fe20de19b..f6afc43843a82 100644
--- a/clang/lib/Analysis/LifetimeSafety/LifetimeAnnotations.cpp
+++ b/clang/lib/Analysis/LifetimeSafety/LifetimeAnnotations.cpp
@@ -99,7 +99,8 @@ bool shouldTrackImplicitObjectArg(const CXXMethodDecl
*Callee) {
if (!isGslPointerType(Callee->getFunctionObjectParameterType()) &&
!isGslOwnerType(Callee->getFunctionObjectParameterType()))
return false;
- if (isPointerLikeType(Callee->getReturnType())) {
+ if (isPointerLikeType(Callee->getReturnType()) &&
+ isGslOwnerType(Callee->getFunctionObjectParameterType())) {
if (!Callee->getIdentifier())
return false;
return llvm::StringSwitch<bool>(Callee->getName())
diff --git a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
index 7634dbf2f6733..b04ed86cd8abd 100644
--- a/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
+++ b/clang/test/Sema/warn-lifetime-analysis-nocfg.cpp
@@ -249,8 +249,10 @@ int &doNotFollowReferencesForLocalOwner() {
return p; // ok
}
+// It is not possible to annotate accessors of view types
+// (like std::string_view::begin()) to catch bugs like the following:
const char *trackThroughMultiplePointer() {
- return std::basic_string_view<char>(std::basic_string<char>()).begin(); //
expected-warning {{returning address of local temporary object}}
+ return std::basic_string_view<char>(std::basic_string<char>()).begin();
}
struct X {
``````````
</details>
https://github.com/llvm/llvm-project/pull/174741
_______________________________________________
cfe-commits mailing list
[email protected]
https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
