[clang] Reapply "[clang analysis][thread-safety] Handle return-by-reference..… (PR #68572)
Clement Courbet via cfe-commits
cfe-commits at lists.llvm.org
Mon Oct 16 23:58:53 PDT 2023
https://github.com/legrosbuffle updated https://github.com/llvm/llvm-project/pull/68572
>From 11f5286f426d082f7fbcb578c0c6cabcd3660453 Mon Sep 17 00:00:00 2001
From: Clement Courbet <courbet at google.com>
Date: Mon, 9 Oct 2023 10:20:12 +0200
Subject: [PATCH] =?UTF-8?q?Reapply=20"[clang=20analysis][thread-safety]=20?=
=?UTF-8?q?Handle=20return-by-reference..=E2=80=A6=20(#68394)"?=
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The new warnings are now under a separate flag `-Wthread-safety-reference-return`. The plan is:
- Start with a period where people can opt into the new warnings with `-Wthread-safety-reference-return` or `-Wthread-safety-beta`. This allows downstream to test the new warnings without having to roll the implementation back and forth.
- Make `-Wthread-safety-reference-return` part of `-Wthread-safety-reference`. People can opt out via `-Wthread-safety-reference -Wnothread-safety-reference-return`.
- (maybe) delete `-Wthread-safety-reference-return` after some time ?
This reverts commit 859f2d032386632562521a99db20923217d98988.
---
.../clang/Analysis/Analyses/ThreadSafety.h | 8 +-
clang/include/clang/Basic/DiagnosticGroups.td | 12 +--
.../clang/Basic/DiagnosticSemaKinds.td | 10 ++-
clang/lib/Analysis/ThreadSafety.cpp | 80 +++++++++++++------
clang/lib/Sema/AnalysisBasedWarnings.cpp | 12 +++
.../SemaCXX/warn-thread-safety-analysis.cpp | 79 ++++++++++++++++++
6 files changed, 168 insertions(+), 33 deletions(-)
diff --git a/clang/include/clang/Analysis/Analyses/ThreadSafety.h b/clang/include/clang/Analysis/Analyses/ThreadSafety.h
index 1808d1d71e05d2c..0866b09bab2995e 100644
--- a/clang/include/clang/Analysis/Analyses/ThreadSafety.h
+++ b/clang/include/clang/Analysis/Analyses/ThreadSafety.h
@@ -47,7 +47,13 @@ enum ProtectedOperationKind {
POK_PassByRef,
/// Passing a pt-guarded variable by reference.
- POK_PtPassByRef
+ POK_PtPassByRef,
+
+ /// Returning a guarded variable by reference.
+ POK_ReturnByRef,
+
+ /// Returning a pt-guarded variable by reference.
+ POK_PtReturnByRef,
};
/// This enum distinguishes between different kinds of lock actions. For
diff --git a/clang/include/clang/Basic/DiagnosticGroups.td b/clang/include/clang/Basic/DiagnosticGroups.td
index 0b09c002191848a..a71afdd710c3bf4 100644
--- a/clang/include/clang/Basic/DiagnosticGroups.td
+++ b/clang/include/clang/Basic/DiagnosticGroups.td
@@ -1061,11 +1061,13 @@ def Most : DiagGroup<"most", [
]>;
// Thread Safety warnings
-def ThreadSafetyAttributes : DiagGroup<"thread-safety-attributes">;
-def ThreadSafetyAnalysis : DiagGroup<"thread-safety-analysis">;
-def ThreadSafetyPrecise : DiagGroup<"thread-safety-precise">;
-def ThreadSafetyReference : DiagGroup<"thread-safety-reference">;
-def ThreadSafetyNegative : DiagGroup<"thread-safety-negative">;
+def ThreadSafetyAttributes : DiagGroup<"thread-safety-attributes">;
+def ThreadSafetyAnalysis : DiagGroup<"thread-safety-analysis">;
+def ThreadSafetyPrecise : DiagGroup<"thread-safety-precise">;
+def ThreadSafetyReferenceReturn : DiagGroup<"thread-safety-reference-return">;
+def ThreadSafetyReference : DiagGroup<"thread-safety-reference",
+ [ThreadSafetyReferenceReturn]>;
+def ThreadSafetyNegative : DiagGroup<"thread-safety-negative">;
def ThreadSafety : DiagGroup<"thread-safety",
[ThreadSafetyAttributes,
ThreadSafetyAnalysis,
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index b211680a0e9b6e9..c777d73dd4a769b 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -3864,7 +3864,7 @@ def warn_fun_requires_negative_cap : Warning<
"calling function %0 requires negative capability '%1'">,
InGroup<ThreadSafetyAnalysis>, DefaultIgnore;
-// Thread safety warnings on pass by reference
+// Thread safety warnings on pass/return by reference
def warn_guarded_pass_by_reference : Warning<
"passing variable %1 by reference requires holding %0 "
"%select{'%2'|'%2' exclusively}3">,
@@ -3873,6 +3873,14 @@ def warn_pt_guarded_pass_by_reference : Warning<
"passing the value that %1 points to by reference requires holding %0 "
"%select{'%2'|'%2' exclusively}3">,
InGroup<ThreadSafetyReference>, DefaultIgnore;
+def warn_guarded_return_by_reference : Warning<
+ "returning variable %1 by reference requires holding %0 "
+ "%select{'%2'|'%2' exclusively}3">,
+ InGroup<ThreadSafetyReferenceReturn>, DefaultIgnore;
+def warn_pt_guarded_return_by_reference : Warning<
+ "returning the value that %1 points to by reference requires holding %0 "
+ "%select{'%2'|'%2' exclusively}3">,
+ InGroup<ThreadSafetyReferenceReturn>, DefaultIgnore;
// Imprecise thread safety warnings
def warn_variable_requires_lock : Warning<
diff --git a/clang/lib/Analysis/ThreadSafety.cpp b/clang/lib/Analysis/ThreadSafety.cpp
index 58dd7113665b132..54d0e95c6bd79a2 100644
--- a/clang/lib/Analysis/ThreadSafety.cpp
+++ b/clang/lib/Analysis/ThreadSafety.cpp
@@ -1008,7 +1008,7 @@ class ThreadSafetyAnalyzer {
threadSafety::SExprBuilder SxBuilder;
ThreadSafetyHandler &Handler;
- const CXXMethodDecl *CurrentMethod = nullptr;
+ const FunctionDecl *CurrentFunction;
LocalVariableMap LocalVarMap;
FactManager FactMan;
std::vector<CFGBlockInfo> BlockInfo;
@@ -1243,10 +1243,10 @@ bool ThreadSafetyAnalyzer::inCurrentScope(const CapabilityExpr &CapE) {
// Members are in scope from methods of the same class.
if (const auto *P = dyn_cast<til::Project>(SExp)) {
- if (!CurrentMethod)
+ if (!isa_and_nonnull<CXXMethodDecl>(CurrentFunction))
return false;
const ValueDecl *VD = P->clangDecl();
- return VD->getDeclContext() == CurrentMethod->getDeclContext();
+ return VD->getDeclContext() == CurrentFunction->getDeclContext();
}
return false;
@@ -1541,6 +1541,8 @@ class BuildLockset : public ConstStmtVisitor<BuildLockset> {
ThreadSafetyAnalyzer *Analyzer;
FactSet FSet;
+ // The fact set for the function on exit.
+ const FactSet &FunctionExitFSet;
/// Maps constructed objects to `this` placeholder prior to initialization.
llvm::SmallDenseMap<const Expr *, til::LiteralPtr *> ConstructedObjects;
LocalVariableMap::Context LVarCtx;
@@ -1566,9 +1568,11 @@ class BuildLockset : public ConstStmtVisitor<BuildLockset> {
bool SkipFirstParam = false);
public:
- BuildLockset(ThreadSafetyAnalyzer *Anlzr, CFGBlockInfo &Info)
+ BuildLockset(ThreadSafetyAnalyzer *Anlzr, CFGBlockInfo &Info,
+ const FactSet &FunctionExitFSet)
: ConstStmtVisitor<BuildLockset>(), Analyzer(Anlzr), FSet(Info.EntrySet),
- LVarCtx(Info.EntryContext), CtxIndex(Info.EntryIndex) {}
+ FunctionExitFSet(FunctionExitFSet), LVarCtx(Info.EntryContext),
+ CtxIndex(Info.EntryIndex) {}
void VisitUnaryOperator(const UnaryOperator *UO);
void VisitBinaryOperator(const BinaryOperator *BO);
@@ -1577,6 +1581,7 @@ class BuildLockset : public ConstStmtVisitor<BuildLockset> {
void VisitCXXConstructExpr(const CXXConstructExpr *Exp);
void VisitDeclStmt(const DeclStmt *S);
void VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *Exp);
+ void VisitReturnStmt(const ReturnStmt *S);
};
} // namespace
@@ -1758,6 +1763,8 @@ void ThreadSafetyAnalyzer::checkPtAccess(const FactSet &FSet, const Expr *Exp,
// Pass by reference warnings are under a different flag.
ProtectedOperationKind PtPOK = POK_VarDereference;
if (POK == POK_PassByRef) PtPOK = POK_PtPassByRef;
+ if (POK == POK_ReturnByRef)
+ PtPOK = POK_PtReturnByRef;
const ValueDecl *D = getValueDecl(Exp);
if (!D || !D->hasAttrs())
@@ -2142,6 +2149,25 @@ void BuildLockset::VisitMaterializeTemporaryExpr(
}
}
+void BuildLockset::VisitReturnStmt(const ReturnStmt *S) {
+ if (Analyzer->CurrentFunction == nullptr)
+ return;
+ const Expr *RetVal = S->getRetValue();
+ if (!RetVal)
+ return;
+
+ // If returning by reference, check that the function requires the appropriate
+ // capabilities.
+ const QualType ReturnType =
+ Analyzer->CurrentFunction->getReturnType().getCanonicalType();
+ if (ReturnType->isLValueReferenceType()) {
+ Analyzer->checkAccess(
+ FunctionExitFSet, RetVal,
+ ReturnType->getPointeeType().isConstQualified() ? AK_Read : AK_Written,
+ POK_ReturnByRef);
+ }
+}
+
/// Given two facts merging on a join point, possibly warn and decide whether to
/// keep or replace.
///
@@ -2251,8 +2277,7 @@ void ThreadSafetyAnalyzer::runAnalysis(AnalysisDeclContext &AC) {
CFG *CFGraph = walker.getGraph();
const NamedDecl *D = walker.getDecl();
- const auto *CurrentFunction = dyn_cast<FunctionDecl>(D);
- CurrentMethod = dyn_cast<CXXMethodDecl>(D);
+ CurrentFunction = dyn_cast<FunctionDecl>(D);
if (D->hasAttr<NoThreadSafetyAnalysisAttr>())
return;
@@ -2278,7 +2303,7 @@ void ThreadSafetyAnalyzer::runAnalysis(AnalysisDeclContext &AC) {
PostOrderCFGView::CFGBlockSet VisitedBlocks(CFGraph);
CFGBlockInfo &Initial = BlockInfo[CFGraph->getEntry().getBlockID()];
- CFGBlockInfo &Final = BlockInfo[CFGraph->getExit().getBlockID()];
+ CFGBlockInfo &Final = BlockInfo[CFGraph->getExit().getBlockID()];
// Mark entry block as reachable
Initial.Reachable = true;
@@ -2348,6 +2373,25 @@ void ThreadSafetyAnalyzer::runAnalysis(AnalysisDeclContext &AC) {
}
}
+ // Compute the expected exit set.
+ // By default, we expect all locks held on entry to be held on exit.
+ FactSet ExpectedFunctionExitSet = Initial.EntrySet;
+
+ // Adjust the expected exit set by adding or removing locks, as declared
+ // by *-LOCK_FUNCTION and UNLOCK_FUNCTION. The intersect below will then
+ // issue the appropriate warning.
+ // FIXME: the location here is not quite right.
+ for (const auto &Lock : ExclusiveLocksAcquired)
+ ExpectedFunctionExitSet.addLock(
+ FactMan, std::make_unique<LockableFactEntry>(Lock, LK_Exclusive,
+ D->getLocation()));
+ for (const auto &Lock : SharedLocksAcquired)
+ ExpectedFunctionExitSet.addLock(
+ FactMan,
+ std::make_unique<LockableFactEntry>(Lock, LK_Shared, D->getLocation()));
+ for (const auto &Lock : LocksReleased)
+ ExpectedFunctionExitSet.removeLock(FactMan, Lock);
+
for (const auto *CurrBlock : *SortedGraph) {
unsigned CurrBlockID = CurrBlock->getBlockID();
CFGBlockInfo *CurrBlockInfo = &BlockInfo[CurrBlockID];
@@ -2407,7 +2451,7 @@ void ThreadSafetyAnalyzer::runAnalysis(AnalysisDeclContext &AC) {
if (!CurrBlockInfo->Reachable)
continue;
- BuildLockset LocksetBuilder(this, *CurrBlockInfo);
+ BuildLockset LocksetBuilder(this, *CurrBlockInfo, ExpectedFunctionExitSet);
// Visit all the statements in the basic block.
for (const auto &BI : *CurrBlock) {
@@ -2483,24 +2527,8 @@ void ThreadSafetyAnalyzer::runAnalysis(AnalysisDeclContext &AC) {
if (!Final.Reachable)
return;
- // By default, we expect all locks held on entry to be held on exit.
- FactSet ExpectedExitSet = Initial.EntrySet;
-
- // Adjust the expected exit set by adding or removing locks, as declared
- // by *-LOCK_FUNCTION and UNLOCK_FUNCTION. The intersect below will then
- // issue the appropriate warning.
- // FIXME: the location here is not quite right.
- for (const auto &Lock : ExclusiveLocksAcquired)
- ExpectedExitSet.addLock(FactMan, std::make_unique<LockableFactEntry>(
- Lock, LK_Exclusive, D->getLocation()));
- for (const auto &Lock : SharedLocksAcquired)
- ExpectedExitSet.addLock(FactMan, std::make_unique<LockableFactEntry>(
- Lock, LK_Shared, D->getLocation()));
- for (const auto &Lock : LocksReleased)
- ExpectedExitSet.removeLock(FactMan, Lock);
-
// FIXME: Should we call this function for all blocks which exit the function?
- intersectAndWarn(ExpectedExitSet, Final.ExitSet, Final.ExitLoc,
+ intersectAndWarn(ExpectedFunctionExitSet, Final.ExitSet, Final.ExitLoc,
LEK_LockedAtEndOfFunction, LEK_NotLockedAtEndOfFunction);
Handler.leaveFunction(CurrentFunction);
diff --git a/clang/lib/Sema/AnalysisBasedWarnings.cpp b/clang/lib/Sema/AnalysisBasedWarnings.cpp
index 77bb560eb6288f7..0947e8b0f526a3b 100644
--- a/clang/lib/Sema/AnalysisBasedWarnings.cpp
+++ b/clang/lib/Sema/AnalysisBasedWarnings.cpp
@@ -1983,6 +1983,12 @@ class ThreadSafetyReporter : public clang::threadSafety::ThreadSafetyHandler {
case POK_PtPassByRef:
DiagID = diag::warn_pt_guarded_pass_by_reference;
break;
+ case POK_ReturnByRef:
+ DiagID = diag::warn_guarded_return_by_reference;
+ break;
+ case POK_PtReturnByRef:
+ DiagID = diag::warn_pt_guarded_return_by_reference;
+ break;
}
PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID) << Kind
<< D
@@ -2013,6 +2019,12 @@ class ThreadSafetyReporter : public clang::threadSafety::ThreadSafetyHandler {
case POK_PtPassByRef:
DiagID = diag::warn_pt_guarded_pass_by_reference;
break;
+ case POK_ReturnByRef:
+ DiagID = diag::warn_guarded_return_by_reference;
+ break;
+ case POK_PtReturnByRef:
+ DiagID = diag::warn_pt_guarded_return_by_reference;
+ break;
}
PartialDiagnosticAt Warning(Loc, S.PDiag(DiagID) << Kind
<< D
diff --git a/clang/test/SemaCXX/warn-thread-safety-analysis.cpp b/clang/test/SemaCXX/warn-thread-safety-analysis.cpp
index 8e312e589d81160..205cfa284f6c9c9 100644
--- a/clang/test/SemaCXX/warn-thread-safety-analysis.cpp
+++ b/clang/test/SemaCXX/warn-thread-safety-analysis.cpp
@@ -5580,6 +5580,85 @@ class Bar {
}
};
+class Return {
+ Mutex mu;
+ Foo foo GUARDED_BY(mu);
+ Foo* foo_ptr PT_GUARDED_BY(mu);
+
+ Foo returns_value_locked() {
+ MutexLock lock(&mu);
+ return foo;
+ }
+
+ Foo returns_value_locks_required() EXCLUSIVE_LOCKS_REQUIRED(mu) {
+ return foo;
+ }
+
+ Foo returns_value_releases_lock_after_return() UNLOCK_FUNCTION(mu) {
+ MutexLock lock(&mu, true);
+ return foo;
+ }
+
+ Foo returns_value_aquires_lock() EXCLUSIVE_LOCK_FUNCTION(mu) {
+ mu.Lock();
+ return foo;
+ }
+
+ Foo returns_value_not_locked() {
+ return foo; // expected-warning {{reading variable 'foo' requires holding mutex 'mu'}}
+ }
+
+ Foo returns_value_releases_lock_before_return() UNLOCK_FUNCTION(mu) {
+ mu.Unlock();
+ return foo; // expected-warning {{reading variable 'foo' requires holding mutex 'mu'}}
+ }
+
+ Foo &returns_ref_not_locked() {
+ return foo; // expected-warning {{returning variable 'foo' by reference requires holding mutex 'mu'}}
+ }
+
+ Foo &returns_ref_locked() {
+ MutexLock lock(&mu);
+ return foo; // expected-warning {{returning variable 'foo' by reference requires holding mutex 'mu'}}
+ }
+
+ Foo &returns_ref_shared_locks_required() SHARED_LOCKS_REQUIRED(mu) {
+ return foo; // expected-warning {{returning variable 'foo' by reference requires holding mutex 'mu' exclusively}}
+ }
+
+ Foo &returns_ref_exclusive_locks_required() EXCLUSIVE_LOCKS_REQUIRED(mu) {
+ return foo;
+ }
+
+ Foo &returns_ref_releases_lock_after_return() UNLOCK_FUNCTION(mu) {
+ MutexLock lock(&mu, true);
+ return foo; // expected-warning {{returning variable 'foo' by reference requires holding mutex 'mu' exclusively}}
+ }
+
+ Foo& returns_ref_releases_lock_before_return() UNLOCK_FUNCTION(mu) {
+ mu.Unlock();
+ return foo; // // expected-warning {{returning variable 'foo' by reference requires holding mutex 'mu' exclusively}}
+ }
+
+ Foo &returns_ref_aquires_lock() EXCLUSIVE_LOCK_FUNCTION(mu) {
+ mu.Lock();
+ return foo;
+ }
+
+ const Foo &returns_constref_shared_locks_required() SHARED_LOCKS_REQUIRED(mu) {
+ return foo;
+ }
+
+ Foo *returns_ptr() {
+ return &foo; // FIXME -- Do we want to warn on this ?
+ }
+
+ Foo &returns_ref2() {
+ return *foo_ptr; // expected-warning {{returning the value that 'foo_ptr' points to by reference requires holding mutex 'mu' exclusively}}
+ }
+
+};
+
} // end namespace PassByRefTest
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