[clang] [coroutines] Detect lifetime issues with coroutine lambda captures (PR #77066)
Utkarsh Saxena via cfe-commits
cfe-commits at lists.llvm.org
Fri Jan 5 02:39:52 PST 2024
https://github.com/usx95 updated https://github.com/llvm/llvm-project/pull/77066
>From 3e0d0ab6c4fc6cba68285816a95e423bc18e8e55 Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena <usx at google.com>
Date: Fri, 5 Jan 2024 10:11:20 +0100
Subject: [PATCH 1/2] [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
>From 0d8d78e30dff896880e674240c8bf47b13c527f5 Mon Sep 17 00:00:00 2001
From: Utkarsh Saxena <usx at google.com>
Date: Fri, 5 Jan 2024 11:39:41 +0100
Subject: [PATCH 2/2] add more test
---
clang/lib/Sema/SemaInit.cpp | 4 ++--
clang/test/SemaCXX/coro-lifetimebound.cpp | 17 +++++++++++++++--
2 files changed, 17 insertions(+), 4 deletions(-)
diff --git a/clang/lib/Sema/SemaInit.cpp b/clang/lib/Sema/SemaInit.cpp
index c100bf11454786..1aa6be826699bb 100644
--- a/clang/lib/Sema/SemaInit.cpp
+++ b/clang/lib/Sema/SemaInit.cpp
@@ -7586,8 +7586,8 @@ static void visitLifetimeBoundArguments(IndirectLocalPath &Path, Expr *Call,
if (ObjectArg) {
bool CheckCoroObjArg = CheckCoroCall;
- // Ignore `__promise.get_return_object()` as it not lifetimebound.
- if (Callee->getDeclName().isIdentifier() &&
+ // Ignore `__promise.get_return_object()` as it is not lifetimebound.
+ if (CheckCoroObjArg && Callee->getDeclName().isIdentifier() &&
Callee->getName() == "get_return_object")
CheckCoroObjArg = false;
// Coroutine lambda objects with empty capture list are not lifetimebound.
diff --git a/clang/test/SemaCXX/coro-lifetimebound.cpp b/clang/test/SemaCXX/coro-lifetimebound.cpp
index 319134450e4b6f..b61013ec057381 100644
--- a/clang/test/SemaCXX/coro-lifetimebound.cpp
+++ b/clang/test/SemaCXX/coro-lifetimebound.cpp
@@ -102,6 +102,10 @@ Co<int> lambda_captures() {
int res = co_await [a](int x, const int& y) -> Co<int> {
co_return x + y + a;
}(1, a);
+ // Lambda object on stack should be fine.
+ auto lamb2 = [a]() -> Co<int> { co_return a; };
+ auto on_stack = lamb2();
+ auto res2 = co_await on_stack;
co_return 1;
}
} // namespace lambdas
@@ -111,7 +115,7 @@ Co<int> lambda_captures() {
// =============================================================================
namespace member_coroutines{
struct S {
- Co<int> member(const int& a) { co_return a; }
+ Co<int> member(const int& a) { co_return a; }
};
Co<int> use() {
@@ -129,6 +133,15 @@ Co<int> use() {
}
} // member_coroutines
+// =============================================================================
+// Safe usage when parameters are value
+// =============================================================================
+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 by_value
+
// =============================================================================
// Lifetime bound but not a Coroutine Return Type: No analysis.
// =============================================================================
@@ -158,7 +171,7 @@ CoNoCRT<int> bar(int a) {
namespace disable_lifetimebound {
Co<int> foo(int x) { co_return x; }
-[[clang::coro_wrapper, clang::coro_disable_lifetimebound]]
+[[clang::coro_wrapper, clang::coro_disable_lifetimebound]]
Co<int> foo_wrapper(const int& x) { return foo(x); }
[[clang::coro_wrapper]] Co<int> caller() {
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