https://github.com/tbaederr created
https://github.com/llvm/llvm-project/pull/120107
We're supposed to let them through and then later diagnose reading from them,
but returning dead pointers is fine.
>From 18b850cd8e6dfce416f7ab40feff3aad9c21a5bf Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Timm=20B=C3=A4der?= <tbae...@redhat.com>
Date: Mon, 16 Dec 2024 16:56:10 +0100
Subject: [PATCH] [clang][bytecode] Don't check returned pointers for liveness
---
clang/lib/AST/ByteCode/Interp.h | 12 ------------
clang/test/AST/ByteCode/functions.cpp | 16 ++++++----------
2 files changed, 6 insertions(+), 22 deletions(-)
diff --git a/clang/lib/AST/ByteCode/Interp.h b/clang/lib/AST/ByteCode/Interp.h
index f085f96fdf5391..2a6ea69475f787 100644
--- a/clang/lib/AST/ByteCode/Interp.h
+++ b/clang/lib/AST/ByteCode/Interp.h
@@ -318,18 +318,6 @@ template <PrimType Name, class T = typename
PrimConv<Name>::T>
bool Ret(InterpState &S, CodePtr &PC) {
const T &Ret = S.Stk.pop<T>();
- // Make sure returned pointers are live. We might be trying to return a
- // pointer or reference to a local variable.
- // Just return false, since a diagnostic has already been emitted in Sema.
- if constexpr (std::is_same_v<T, Pointer>) {
- // FIXME: We could be calling isLive() here, but the emitted diagnostics
- // seem a little weird, at least if the returned expression is of
- // pointer type.
- // Null pointers are considered live here.
- if (!Ret.isZero() && !Ret.isLive())
- return false;
- }
-
assert(S.Current);
assert(S.Current->getFrameOffset() == S.Stk.size() && "Invalid frame");
if (!S.checkingPotentialConstantExpression() || S.Current->Caller)
diff --git a/clang/test/AST/ByteCode/functions.cpp
b/clang/test/AST/ByteCode/functions.cpp
index b00f59a8d8d433..10bea3a0d017e2 100644
--- a/clang/test/AST/ByteCode/functions.cpp
+++ b/clang/test/AST/ByteCode/functions.cpp
@@ -303,21 +303,17 @@ namespace ReturnLocalPtr {
return &a; // both-warning {{address of stack memory}}
}
- /// GCC rejects the expression below, just like the new interpreter. The
current interpreter
- /// however accepts it and only warns about the function above returning an
address to stack
- /// memory. If we change the condition to 'p() != nullptr', it even succeeds.
- static_assert(p() == nullptr, ""); // ref-error {{static assertion failed}} \
- // expected-error {{not an integral
constant expression}}
-
- /// FIXME: The current interpreter emits diagnostics in the reference case
below, but the
- /// new one does not.
+ /// FIXME: Both interpreters should diagnose this. We're returning a pointer
to a local
+ /// variable.
+ static_assert(p() == nullptr, ""); // both-error {{static assertion failed}}
+
constexpr const int &p2() {
- int a = 12; // ref-note {{declared here}}
+ int a = 12; // both-note {{declared here}}
return a; // both-warning {{reference to stack memory associated with
local variable}}
}
static_assert(p2() == 12, ""); // both-error {{not an integral constant
expression}} \
- // ref-note {{read of variable whose lifetime
has ended}}
+ // both-note {{read of variable whose
lifetime has ended}}
}
namespace VoidReturn {
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