[clang] Diagnose use of VLAs in a coroutine (PR #70341)
Aaron Ballman via cfe-commits
cfe-commits at lists.llvm.org
Thu Oct 26 08:47:45 PDT 2023
https://github.com/AaronBallman updated https://github.com/llvm/llvm-project/pull/70341
>From f068b471efa81d60d1d6e2c98da56be58958a015 Mon Sep 17 00:00:00 2001
From: Aaron Ballman <aaron at aaronballman.com>
Date: Thu, 26 Oct 2023 10:53:06 -0400
Subject: [PATCH 1/2] Diagnose use of VLAs in a coroutine
Fixes https://github.com/llvm/llvm-project/issues/65858
---
.../clang/Basic/DiagnosticSemaKinds.td | 2 ++
clang/include/clang/Sema/ScopeInfo.h | 8 +++++
clang/lib/Sema/SemaCoroutine.cpp | 5 ++++
clang/lib/Sema/SemaType.cpp | 18 ++++++++----
clang/test/SemaCXX/coroutine-vla.cpp | 29 +++++++++++++++++++
5 files changed, 56 insertions(+), 6 deletions(-)
create mode 100644 clang/test/SemaCXX/coroutine-vla.cpp
diff --git a/clang/include/clang/Basic/DiagnosticSemaKinds.td b/clang/include/clang/Basic/DiagnosticSemaKinds.td
index a673ce726d6c220..453bd8a9a340425 100644
--- a/clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -166,6 +166,8 @@ def ext_vla_folded_to_constant : ExtWarn<
InGroup<GNUFoldingConstant>;
def err_vla_unsupported : Error<
"variable length arrays are not supported for %select{the current target|'%1'}0">;
+def err_vla_in_coroutine_unsupported : Error<
+ "variable length arrays in a coroutine are not supported">;
def note_vla_unsupported : Note<
"variable length arrays are not supported for the current target">;
diff --git a/clang/include/clang/Sema/ScopeInfo.h b/clang/include/clang/Sema/ScopeInfo.h
index 02b22af89ff035d..b2f6e3289f41fce 100644
--- a/clang/include/clang/Sema/ScopeInfo.h
+++ b/clang/include/clang/Sema/ScopeInfo.h
@@ -189,6 +189,9 @@ class FunctionScopeInfo {
/// First SEH '__try' statement in the current function.
SourceLocation FirstSEHTryLoc;
+ /// First use of a VLA within the current function.
+ SourceLocation FirstVLALoc;
+
private:
/// Used to determine if errors occurred in this function or block.
DiagnosticErrorTrap ErrorTrap;
@@ -473,6 +476,11 @@ class FunctionScopeInfo {
FirstSEHTryLoc = TryLoc;
}
+ void setHasVLA(SourceLocation VLALoc) {
+ if (FirstVLALoc.isInvalid())
+ FirstVLALoc = VLALoc;
+ }
+
bool NeedsScopeChecking() const {
return !HasDroppedStmt && (HasIndirectGoto || HasMustTail ||
(HasBranchProtectedScope && HasBranchIntoScope));
diff --git a/clang/lib/Sema/SemaCoroutine.cpp b/clang/lib/Sema/SemaCoroutine.cpp
index d2b0922a4bb9c4c..e1f3b5acb3cadec 100644
--- a/clang/lib/Sema/SemaCoroutine.cpp
+++ b/clang/lib/Sema/SemaCoroutine.cpp
@@ -1198,6 +1198,11 @@ void Sema::CheckCompletedCoroutineBody(FunctionDecl *FD, Stmt *&Body) {
if (FD->hasAttr<AlwaysInlineAttr>())
Diag(FD->getLocation(), diag::warn_always_inline_coroutine);
+ // We don't allow use of VLAs within a coroutine, so diagnose if we've seen
+ // a VLA in the body of this function.
+ if (Fn->FirstVLALoc.isValid())
+ Diag(Fn->FirstVLALoc, diag::err_vla_in_coroutine_unsupported);
+
// [stmt.return.coroutine]p1:
// A coroutine shall not enclose a return statement ([stmt.return]).
if (Fn->FirstReturnLoc.isValid()) {
diff --git a/clang/lib/Sema/SemaType.cpp b/clang/lib/Sema/SemaType.cpp
index 28b81c1768a3004..dea77fae4cadb59 100644
--- a/clang/lib/Sema/SemaType.cpp
+++ b/clang/lib/Sema/SemaType.cpp
@@ -2706,12 +2706,18 @@ QualType Sema::BuildArrayType(QualType T, ArrayType::ArraySizeModifier ASM,
}
}
- if (T->isVariableArrayType() && !Context.getTargetInfo().isVLASupported()) {
- // CUDA device code and some other targets don't support VLAs.
- bool IsCUDADevice = (getLangOpts().CUDA && getLangOpts().CUDAIsDevice);
- targetDiag(Loc,
- IsCUDADevice ? diag::err_cuda_vla : diag::err_vla_unsupported)
- << (IsCUDADevice ? CurrentCUDATarget() : 0);
+ if (T->isVariableArrayType()) {
+ if (!Context.getTargetInfo().isVLASupported()) {
+ // CUDA device code and some other targets don't support VLAs.
+ bool IsCUDADevice = (getLangOpts().CUDA && getLangOpts().CUDAIsDevice);
+ targetDiag(Loc,
+ IsCUDADevice ? diag::err_cuda_vla : diag::err_vla_unsupported)
+ << (IsCUDADevice ? CurrentCUDATarget() : 0);
+ } else if (sema::FunctionScopeInfo *FSI = getCurFunction()) {
+ // VLAs are supported on this target, but we may need to do delayed
+ // checking that the VLA is not being used within a coroutine.
+ FSI->setHasVLA(Loc);
+ }
}
// If this is not C99, diagnose array size modifiers on non-VLAs.
diff --git a/clang/test/SemaCXX/coroutine-vla.cpp b/clang/test/SemaCXX/coroutine-vla.cpp
new file mode 100644
index 000000000000000..176e35f346e2b45
--- /dev/null
+++ b/clang/test/SemaCXX/coroutine-vla.cpp
@@ -0,0 +1,29 @@
+// RUN: %clang_cc1 %s -std=c++20 -fsyntax-only -Wno-vla-cxx-extension -verify
+#include "Inputs/std-coroutine.h"
+
+struct promise;
+
+struct coroutine : std::coroutine_handle<promise> {
+ using promise_type = ::promise;
+};
+
+struct promise
+{
+ coroutine get_return_object();
+ std::suspend_always initial_suspend() noexcept;
+ std::suspend_always final_suspend() noexcept;
+ void return_void();
+ void unhandled_exception();
+};
+
+coroutine foo(int n) {
+ int array[n]; // expected-error {{variable length arrays in a coroutine are not supported}}
+ co_return;
+}
+
+void lambda() {
+ [](int n) -> coroutine {
+ int array[n]; // expected-error {{variable length arrays in a coroutine are not supported}}
+ co_return;
+ }(10);
+}
>From 123789ebe3a3c01db54e77ed7c95f47775375f53 Mon Sep 17 00:00:00 2001
From: Aaron Ballman <aaron at aaronballman.com>
Date: Thu, 26 Oct 2023 11:47:17 -0400
Subject: [PATCH 2/2] Update comment + add release note
---
clang/docs/ReleaseNotes.rst | 4 ++++
clang/lib/Sema/SemaCoroutine.cpp | 4 ++--
2 files changed, 6 insertions(+), 2 deletions(-)
diff --git a/clang/docs/ReleaseNotes.rst b/clang/docs/ReleaseNotes.rst
index c0514e5b70783b6..3af16e40a96b79d 100644
--- a/clang/docs/ReleaseNotes.rst
+++ b/clang/docs/ReleaseNotes.rst
@@ -629,6 +629,10 @@ Bug Fixes to C++ Support
(`#46200 <https://github.com/llvm/llvm-project/issues/46200>`_)
(`#57812 <https://github.com/llvm/llvm-project/issues/57812>`_)
+- Diagnose use of a variable-length array in a coroutine. The design of
+ coroutines is such that it is not possible to support VLA use. Fixes:
+ (`#65858 <https://github.com/llvm/llvm-project/issues/65858>`_)
+
Bug Fixes to AST Handling
^^^^^^^^^^^^^^^^^^^^^^^^^
- Fixed an import failure of recursive friend class template.
diff --git a/clang/lib/Sema/SemaCoroutine.cpp b/clang/lib/Sema/SemaCoroutine.cpp
index e1f3b5acb3cadec..cfaa93fbea4dd37 100644
--- a/clang/lib/Sema/SemaCoroutine.cpp
+++ b/clang/lib/Sema/SemaCoroutine.cpp
@@ -1198,8 +1198,8 @@ void Sema::CheckCompletedCoroutineBody(FunctionDecl *FD, Stmt *&Body) {
if (FD->hasAttr<AlwaysInlineAttr>())
Diag(FD->getLocation(), diag::warn_always_inline_coroutine);
- // We don't allow use of VLAs within a coroutine, so diagnose if we've seen
- // a VLA in the body of this function.
+ // The design of coroutines means we cannot allow use of VLAs within one, so
+ // diagnose if we've seen a VLA in the body of this function.
if (Fn->FirstVLALoc.isValid())
Diag(Fn->FirstVLALoc, diag::err_vla_in_coroutine_unsupported);
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