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[clang][bytecode] Check for unknown size array pointers in InitField* #154689

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Merged
merged 1 commit into from
Aug 21, 2025
Merged

[clang][bytecode] Check for unknown size array pointers in InitField* #154689

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22 changes: 20 additions & 2 deletions clang/lib/AST/ByteCode/Interp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -1640,6 +1640,9 @@ bool InitField(InterpState &S, CodePtr OpPC, uint32_t I) {
const Pointer &Ptr = S.Stk.peek<Pointer>();
if (!CheckRange(S, OpPC, Ptr, CSK_Field))
return false;
if (!CheckArray(S, OpPC, Ptr))
return false;

const Pointer &Field = Ptr.atField(I);
Field.deref<T>() = Value;
Field.initialize();
Expand All @@ -1652,6 +1655,9 @@ bool InitFieldActivate(InterpState &S, CodePtr OpPC, uint32_t I) {
const Pointer &Ptr = S.Stk.peek<Pointer>();
if (!CheckRange(S, OpPC, Ptr, CSK_Field))
return false;
if (!CheckArray(S, OpPC, Ptr))
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@shafik shafik Aug 21, 2025

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I feel like CheckArray is really DiagnoseIfArrayOfUnknownSize a mouthful for sure.

return false;

const Pointer &Field = Ptr.atField(I);
Field.deref<T>() = Value;
Field.activate();
Expand All @@ -1663,7 +1669,13 @@ template <PrimType Name, class T = typename PrimConv<Name>::T>
bool InitBitField(InterpState &S, CodePtr OpPC, const Record::Field *F) {
assert(F->isBitField());
const T &Value = S.Stk.pop<T>();
const Pointer &Field = S.Stk.peek<Pointer>().atField(F->Offset);
const Pointer &Ptr = S.Stk.peek<Pointer>();
if (!CheckRange(S, OpPC, Ptr, CSK_Field))
return false;
if (!CheckArray(S, OpPC, Ptr))
return false;

const Pointer &Field = Ptr.atField(F->Offset);

if constexpr (needsAlloc<T>()) {
T Result = S.allocAP<T>(Value.bitWidth());
Expand All @@ -1689,7 +1701,13 @@ bool InitBitFieldActivate(InterpState &S, CodePtr OpPC,
const Record::Field *F) {
assert(F->isBitField());
const T &Value = S.Stk.pop<T>();
const Pointer &Field = S.Stk.peek<Pointer>().atField(F->Offset);
const Pointer &Ptr = S.Stk.peek<Pointer>();
if (!CheckRange(S, OpPC, Ptr, CSK_Field))
return false;
if (!CheckArray(S, OpPC, Ptr))
return false;

const Pointer &Field = Ptr.atField(F->Offset);

if constexpr (needsAlloc<T>()) {
T Result = S.allocAP<T>(Value.bitWidth());
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20 changes: 20 additions & 0 deletions clang/test/AST/ByteCode/arrays.cpp
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Expand Up @@ -800,3 +800,23 @@ namespace ZeroSizeArrayRead {
static_assert(s[0] == '0', ""); // both-error {{not an integral constant expression}} \
// both-note {{read of dereferenced one-past-the-end pointer}}
}

namespace FAM {
char *strchr(const char *, int);

struct A {
char n, a[2];
};
struct B {
int n;
struct A a[]; // both-note {{here}}
};

const struct B b = {0, {{1, {2, 3}}, {4, {5, 6}}}};
void foo(void) { int sch = 0 != strchr(b.a[1].a, '\0'); }

int foo2() {
struct B b = {0, {{1, {2, 3}}, {4, {5, 6}}}}; // both-error {{initialization of flexible array member is not allowed}}
return 1;
}
}