[analyzer] Make it a noop when initializing a field of empty record #138594
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
…cord. Previously, Static Analyzer initializes empty type fields with zeroes. This can cause problems when those fields have no unique addresses. For example, llvm#137252. rdar://146753089
llvmbot
added
clang
Member
|
@llvm/pr-subscribers-clang @llvm/pr-subscribers-clang-static-analyzer-1 Author: Ziqing Luo (ziqingluo-90) ChangesPreviously, Static Analyzer initializes empty type fields with zeroes. This can cause problems when those fields have no unique addresses. For example, #137252. rdar://146753089 Full diff: https://github.com/llvm/llvm-project/pull/138594.diff 2 Files Affected:
diff --git a/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp b/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
index 92ce3fa2225c8..219d7b4d2278c 100644
--- a/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
+++ b/clang/lib/StaticAnalyzer/Core/ExprEngineCXX.cpp
@@ -10,6 +10,7 @@
//
//===----------------------------------------------------------------------===//
+#include "clang/AST/ASTContext.h"
#include "clang/AST/AttrIterator.h"
#include "clang/AST/DeclCXX.h"
#include "clang/AST/ParentMap.h"
@@ -700,6 +701,7 @@ void ExprEngine::handleConstructor(const Expr *E,
if (CE) {
// FIXME: Is it possible and/or useful to do this before PreStmt?
StmtNodeBuilder Bldr(DstPreVisit, PreInitialized, *currBldrCtx);
+ ASTContext &Ctx = LCtx->getAnalysisDeclContext()->getASTContext();
for (ExplodedNode *N : DstPreVisit) {
ProgramStateRef State = N->getState();
if (CE->requiresZeroInitialization()) {
@@ -715,7 +717,11 @@ void ExprEngine::handleConstructor(const Expr *E,
// actually make things worse. Placement new makes this tricky as well,
// since it's then possible to be initializing one part of a multi-
// dimensional array.
- State = State->bindDefaultZero(Target, LCtx);
+ const CXXRecordDecl *TargetHeldRecord =
+ Target.getType(Ctx)->getPointeeCXXRecordDecl();
+
+ if (!TargetHeldRecord || !TargetHeldRecord->isEmpty())
+ State = State->bindDefaultZero(Target, LCtx);
}
Bldr.generateNode(CE, N, State, /*tag=*/nullptr,
diff --git a/clang/test/Analysis/issue-137252.cpp b/clang/test/Analysis/issue-137252.cpp
new file mode 100644
index 0000000000000..8064e3f54d9fd
--- /dev/null
+++ b/clang/test/Analysis/issue-137252.cpp
@@ -0,0 +1,45 @@
+// RUN: %clang_analyze_cc1 -analyzer-checker=cplusplus -verify %s
+// RUN: %clang_analyze_cc1 -analyzer-checker=cplusplus -verify %s -DEMPTY_CLASS
+
+// expected-no-diagnostics
+
+// This test reproduces the issue that previously the static analyzer
+// initialized an [[__no_unique_address__]] empty field to zero,
+// over-writing a non-empty field with the same offset.
+
+namespace std {
+#ifdef EMPTY_CLASS
+
+ template <typename T>
+ class default_delete {
+ T dump();
+ static T x;
+ };
+ template <class _Tp, class _Dp = default_delete<_Tp> >
+#else
+
+ struct default_delete {};
+ template <class _Tp, class _Dp = default_delete >
+#endif
+ class unique_ptr {
+ [[__no_unique_address__]] _Tp * __ptr_;
+ [[__no_unique_address__]] _Dp __deleter_;
+
+ public:
+ explicit unique_ptr(_Tp* __p) noexcept
+ : __ptr_(__p),
+ __deleter_() {}
+
+ ~unique_ptr() {
+ delete __ptr_;
+ }
+ };
+}
+
+struct X {};
+
+int main()
+{
+ std::unique_ptr<X> a(new X()); // previously leak falsely reported
+ return 0;
+}
|
Contributor
Author
|
CC: @dtarditi |
isuckatcs
reviewed
May 6, 2025
steakhal
requested changes
May 6, 2025
Contributor
steakhal
left a comment
steakhal
left a comment
There was a problem hiding this comment.
Thank you for your contribution, and debugging the case.
Left a couple of comments inline.
steakhal
reviewed
May 7, 2025
Contributor
|
LGTM. @ziqingluo-90 thank you for fixing this problem! |
steakhal
changed the title
steakhal
approved these changes
May 7, 2025
Contributor
steakhal
left a comment
steakhal
left a comment
There was a problem hiding this comment.
Indeed, it looks great now. Thank you!
Let's merge this.
Collaborator
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/144/builds/24534 Here is the relevant piece of the build log for the reference |
Member
|
Sorry for the post-merge comment, but can we please wait for the CI to finish before merging a patch, so that we can check if everything is fine? Apparently, we broke the trunk. |
isuckatcs
reviewed
May 7, 2025
Comment on lines
+719
to
+720
| const CXXRecordDecl *TargetHeldRecord = | ||
| cast<CXXRecordDecl>(CE->getType()->getAsRecordDecl()); |
Member
There was a problem hiding this comment.
This cast can actually fail. See the broken testcase:
llvm-project/llvm/include/llvm/Support/Casting.h:109: static bool llvm::isa_impl_cl<To, const From*>::doit(const From*) [with To = clang::CXXRecordDecl; From = clang::RecordDecl]: Assertion `Val && "isa<> used on a null pointer"' failed.
It happened in an Objective-C test though.
struct raw_pair {
int p1;
int p2;
};
void testArrayNew() {
raw_pair *p = new raw_pair[2]();
clang_analyzer_eval(p[0].p1 == 0); // expected-warning{{TRUE}}
clang_analyzer_eval(p[0].p2 == 0); // expected-warning{{TRUE}}
clang_analyzer_eval(p[1].p1 == 0); // expected-warning{{TRUE}}
clang_analyzer_eval(p[1].p2 == 0); // expected-warning{{TRUE}}
}
Contributor
Author
There was a problem hiding this comment.
Thanks for the heads up. I re-landed the commit: b756c82
steakhal
added a commit
that referenced
this pull request
May 7, 2025
…record" (#138951) Reverts #138594 Crashes, see: https://lab.llvm.org/buildbot/#/builders/144/builds/24534
llvm-sync bot
pushed a commit
to arm/arm-toolchain
that referenced
this pull request
May 7, 2025
…d of empty record" (#138951) Reverts llvm/llvm-project#138594 Crashes, see: https://lab.llvm.org/buildbot/#/builders/144/builds/24534
Contributor
Author
|
Re-landed: b756c82 |
Collaborator
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/60/builds/26748 Here is the relevant piece of the build log for the reference |
Collaborator
|
LLVM Buildbot has detected a new failure on builder Full details are available at: https://lab.llvm.org/buildbot/#/builders/56/builds/25255 Here is the relevant piece of the build log for the reference |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
6 participants
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Previously, Static Analyzer initializes empty type fields with zeroes. This can cause problems when those fields have no unique addresses. For example, #137252.
rdar://146753089