https://github.com/usx95 created https://github.com/llvm/llvm-project/pull/77066
This came up in the discussion with seastar folks on RFC Fixes https://github.com/llvm/llvm-project/issues/76995 >From 3e0d0ab6c4fc6cba68285816a95e423bc18e8e55 Mon Sep 17 00:00:00 2001 From: Utkarsh Saxena <u...@google.com> Date: Fri, 5 Jan 2024 10:11:20 +0100 Subject: [PATCH] [coroutines] Detect lifetime issues with coroutine lambda captures --- clang/lib/Sema/SemaInit.cpp | 20 +++++-- clang/test/SemaCXX/coro-lifetimebound.cpp | 64 +++++++++++++++++++++-- 2 files changed, 76 insertions(+), 8 deletions(-) diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp index 60c0e3e74204ec..c100bf11454786 100644 --- a/clang/lib/Sema/SemaInit.cpp +++ b/clang/lib/Sema/SemaInit.cpp @@ -12,6 +12,7 @@ #include "clang/AST/ASTContext.h" #include "clang/AST/DeclObjC.h" +#include "clang/AST/Expr.h" #include "clang/AST/ExprCXX.h" #include "clang/AST/ExprObjC.h" #include "clang/AST/ExprOpenMP.h" @@ -33,6 +34,7 @@ #include "llvm/ADT/SmallString.h" #include "llvm/ADT/SmallVector.h" #include "llvm/ADT/StringExtras.h" +#include "llvm/Support/Casting.h" #include "llvm/Support/ErrorHandling.h" #include "llvm/Support/raw_ostream.h" @@ -7575,15 +7577,27 @@ static void visitLifetimeBoundArguments(IndirectLocalPath &Path, Expr *Call, Path.pop_back(); }; - if (ObjectArg && implicitObjectParamIsLifetimeBound(Callee)) - VisitLifetimeBoundArg(Callee, ObjectArg); - bool CheckCoroCall = false; if (const auto *RD = Callee->getReturnType()->getAsRecordDecl()) { CheckCoroCall = RD->hasAttr<CoroLifetimeBoundAttr>() && RD->hasAttr<CoroReturnTypeAttr>() && !Callee->hasAttr<CoroDisableLifetimeBoundAttr>(); } + + if (ObjectArg) { + bool CheckCoroObjArg = CheckCoroCall; + // Ignore `__promise.get_return_object()` as it not lifetimebound. + if (Callee->getDeclName().isIdentifier() && + Callee->getName() == "get_return_object") + CheckCoroObjArg = false; + // Coroutine lambda objects with empty capture list are not lifetimebound. + if (auto *LE = dyn_cast<LambdaExpr>(ObjectArg->IgnoreImplicit()); + LE && LE->captures().empty()) + CheckCoroObjArg = false; + if (implicitObjectParamIsLifetimeBound(Callee) || CheckCoroObjArg) + VisitLifetimeBoundArg(Callee, ObjectArg); + } + for (unsigned I = 0, N = std::min<unsigned>(Callee->getNumParams(), Args.size()); I != N; ++I) { diff --git a/clang/test/SemaCXX/coro-lifetimebound.cpp b/clang/test/SemaCXX/coro-lifetimebound.cpp index 3fc7ca70a14a12..319134450e4b6f 100644 --- a/clang/test/SemaCXX/coro-lifetimebound.cpp +++ b/clang/test/SemaCXX/coro-lifetimebound.cpp @@ -64,6 +64,10 @@ Co<int> bar_coro(const int &b, int c) { : bar_coro(0, 1); // expected-warning {{returning address of local temporary object}} } +// ============================================================================= +// Lambdas +// ============================================================================= +namespace lambdas { void lambdas() { auto unsafe_lambda = [] [[clang::coro_wrapper]] (int b) { return foo_coro(b); // expected-warning {{address of stack memory associated with parameter}} @@ -84,15 +88,47 @@ void lambdas() { co_return x + co_await foo_coro(b); }; } + +Co<int> lambda_captures() { + int a = 1; + // Temporary lambda object dies. + auto lamb = [a](int x, const int& y) -> Co<int> { // expected-warning {{temporary whose address is used as value of local variable 'lamb'}} + co_return x + y + a; + }(1, a); + // Object dies but it has no capture. + auto no_capture = []() -> Co<int> { co_return 1; }(); + auto bad_no_capture = [](const int& a) -> Co<int> { co_return a; }(1); // expected-warning {{temporary}} + // Temporary lambda object with lifetime extension under co_await. + int res = co_await [a](int x, const int& y) -> Co<int> { + co_return x + y + a; + }(1, a); + co_return 1; +} +} // namespace lambdas + // ============================================================================= -// Safe usage when parameters are value +// Member coroutines // ============================================================================= -namespace by_value { -Co<int> value_coro(int b) { co_return co_await foo_coro(b); } -[[clang::coro_wrapper]] Co<int> wrapper1(int b) { return value_coro(b); } -[[clang::coro_wrapper]] Co<int> wrapper2(const int& b) { return value_coro(b); } +namespace member_coroutines{ +struct S { + Co<int> member(const int& a) { co_return a; } +}; + +Co<int> use() { + S s; + int a = 1; + auto test1 = s.member(1); // expected-warning {{temporary whose address is used as value of local variable}} + auto test2 = s.member(a); + auto test3 = S{}.member(a); // expected-warning {{temporary whose address is used as value of local variable}} + co_return 1; } +[[clang::coro_wrapper]] Co<int> wrapper(const int& a) { + S s; + return s.member(a); // expected-warning {{address of stack memory}} +} +} // member_coroutines + // ============================================================================= // Lifetime bound but not a Coroutine Return Type: No analysis. // ============================================================================= @@ -129,4 +165,22 @@ Co<int> foo_wrapper(const int& x) { return foo(x); } // The call to foo_wrapper is wrapper is safe. return foo_wrapper(1); } + +struct S{ +[[clang::coro_wrapper, clang::coro_disable_lifetimebound]] +Co<int> member(const int& x) { return foo(x); } +}; + +Co<int> use() { + S s; + int a = 1; + auto test1 = s.member(1); // param is not flagged. + auto test2 = S{}.member(a); // 'this' is not flagged. + co_return 1; +} + +[[clang::coro_wrapper]] Co<int> return_stack_addr(const int& a) { + S s; + return s.member(a); // return of stack addr is not flagged. +} } // namespace disable_lifetimebound _______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
