Author: Marco Elver Date: 2025-02-26T16:34:33+01:00 New Revision: 3c8c0d4d8d9bbc160d160e683f7a74fd28574dc6
URL: https://github.com/llvm/llvm-project/commit/3c8c0d4d8d9bbc160d160e683f7a74fd28574dc6 DIFF: https://github.com/llvm/llvm-project/commit/3c8c0d4d8d9bbc160d160e683f7a74fd28574dc6.diff LOG: Thread Safety Analysis: Handle address-of followed by dereference Correctly analyze expressions where the address of a guarded variable is taken and immediately dereferenced, such as (*(type-specifier *)&x). Previously, such patterns would result in false negatives. Pull Request: https://github.com/llvm/llvm-project/pull/127396 Added: Modified: clang/lib/Analysis/ThreadSafety.cpp clang/test/Sema/warn-thread-safety-analysis.c Removed: ################################################################################ diff --git a/clang/lib/Analysis/ThreadSafety.cpp b/clang/lib/Analysis/ThreadSafety.cpp index bfaf1a0e7c7ff..1bad4eac23c68 100644 --- a/clang/lib/Analysis/ThreadSafety.cpp +++ b/clang/lib/Analysis/ThreadSafety.cpp @@ -1765,6 +1765,8 @@ void ThreadSafetyAnalyzer::checkAccess(const FactSet &FSet, const Expr *Exp, void ThreadSafetyAnalyzer::checkPtAccess(const FactSet &FSet, const Expr *Exp, AccessKind AK, ProtectedOperationKind POK) { + // Strip off paren- and cast-expressions, checking if we encounter any other + // operator that should be delegated to checkAccess() instead. while (true) { if (const auto *PE = dyn_cast<ParenExpr>(Exp)) { Exp = PE->getSubExpr(); @@ -1783,6 +1785,15 @@ void ThreadSafetyAnalyzer::checkPtAccess(const FactSet &FSet, const Expr *Exp, break; } + if (const auto *UO = dyn_cast<UnaryOperator>(Exp)) { + if (UO->getOpcode() == UO_AddrOf) { + // Pointer access via pointer taken of variable, so the dereferenced + // variable is not actually a pointer. + checkAccess(FSet, UO->getSubExpr(), AK, POK); + return; + } + } + // Pass by reference warnings are under a diff erent flag. ProtectedOperationKind PtPOK = POK_VarDereference; if (POK == POK_PassByRef) PtPOK = POK_PtPassByRef; diff --git a/clang/test/Sema/warn-thread-safety-analysis.c b/clang/test/Sema/warn-thread-safety-analysis.c index 73b4e4798f644..46495ad4889b4 100644 --- a/clang/test/Sema/warn-thread-safety-analysis.c +++ b/clang/test/Sema/warn-thread-safety-analysis.c @@ -24,6 +24,9 @@ __attribute__ ((shared_locks_required(__VA_ARGS__))) #define NO_THREAD_SAFETY_ANALYSIS __attribute__ ((no_thread_safety_analysis)) +#define __READ_ONCE(x) (*(const volatile __typeof__(x) *)&(x)) +#define __WRITE_ONCE(x, val) do { *(volatile __typeof__(x) *)&(x) = (val); } while (0) + // Define the mutex struct. // Simplified only for test purpose. struct LOCKABLE Mutex {}; @@ -142,9 +145,25 @@ int main(void) { (void)(get_value(b_) == 1); mutex_unlock(foo_.mu_); + a_ = 0; // expected-warning{{writing variable 'a_' requires holding mutex 'foo_.mu_'}} + __WRITE_ONCE(a_, 0); // expected-warning{{writing variable 'a_' requires holding mutex 'foo_.mu_'}} + (void)(a_ == 0); // expected-warning{{reading variable 'a_' requires holding mutex 'foo_.mu_'}} + (void)(__READ_ONCE(a_) == 0); // expected-warning{{reading variable 'a_' requires holding mutex 'foo_.mu_'}} + *b_ = 0; // expected-warning{{writing the value pointed to by 'b_' requires holding mutex 'foo_.mu_' exclusively}} + __WRITE_ONCE(*b_, 0); // expected-warning{{writing the value pointed to by 'b_' requires holding mutex 'foo_.mu_' exclusively}} + (void)(*b_ == 0); // expected-warning{{reading the value pointed to by 'b_' requires holding mutex 'foo_.mu_'}} + (void)(__READ_ONCE(*b_) == 0); // expected-warning{{reading the value pointed to by 'b_' requires holding mutex 'foo_.mu_'}} c_ = 0; // expected-warning{{writing variable 'c_' requires holding any mutex exclusively}} (void)(*d_ == 0); // expected-warning{{reading the value pointed to by 'd_' requires holding any mutex}} mutex_exclusive_lock(foo_.mu_); + a_ = 0; + __WRITE_ONCE(a_, 0); + (void)(a_ == 0); + (void)(__READ_ONCE(a_) == 0); + *b_ = 0; + __WRITE_ONCE(*b_, 0); + (void)(*b_ == 0); + (void)(__READ_ONCE(*b_) == 0); c_ = 1; (void)(*d_ == 1); mutex_unlock(foo_.mu_); _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
