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[clang][bytecode] Fix null Descriptor dereference in ArrayElemPtrPop #163386

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Merged
merged 3 commits into from
Oct 16, 2025
Merged

[clang][bytecode] Fix null Descriptor dereference in ArrayElemPtrPop #163386

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7e74074
[clang][Interp] Fix null Descriptor dereference in ArrayElemPtrPop
term-est Oct 14, 2025
0076d68
[clang][Interp] Add regression test for crash with typeid pointers
term-est Oct 15, 2025
dae76b1
[clang][Interp] ArrayElemPtr should also do null check on the descriptor
term-est Oct 15, 2025
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6 changes: 4 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 @@ -3096,7 +3096,8 @@ inline bool ArrayElemPtr(InterpState &S, CodePtr OpPC) {
}

if (Offset.isZero()) {
if (Ptr.getFieldDesc()->isArray() && Ptr.getIndex() == 0) {
if (const Descriptor *Desc = Ptr.getFieldDesc();
Desc && Desc->isArray() && Ptr.getIndex() == 0) {
S.Stk.push<Pointer>(Ptr.atIndex(0).narrow());
return true;
}
Expand Down Expand Up @@ -3126,7 +3127,8 @@ inline bool ArrayElemPtrPop(InterpState &S, CodePtr OpPC) {
}

if (Offset.isZero()) {
if (Ptr.getFieldDesc()->isArray() && Ptr.getIndex() == 0) {
if (const Descriptor *Desc = Ptr.getFieldDesc();
Desc && Desc->isArray() && Ptr.getIndex() == 0) {
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You need to do the same change in ArrayElemPtr above.

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added with dae76b1

Do you think we need this kind of check for each use of getFieldDesc? Or the other uses are not supposed to be null
If so, I think we need some assertions

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No it's fine.

S.Stk.push<Pointer>(Ptr.atIndex(0).narrow());
return true;
}
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10 changes: 10 additions & 0 deletions clang/test/AST/ByteCode/typeid.cpp
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Expand Up @@ -59,3 +59,13 @@ namespace TypeidPtrInEvaluationResult {
consteval const std::type_info *ftype_info() { return &typeid(c); }
const std::type_info *T1 = ftype_info();
}

// Regression test for crash in ArrayElemPtrPop with typeid pointers. GH-163127
namespace TypeidPtrRegression {
void dontcrash() {
// this should just be an error and not an ICE
constexpr auto res = ((void**)&typeid(int))[0]; // both-error {{must be initialized by a constant expression}} \
// both-note {{cast that performs the conversions of a reinterpret_cast is not allowed in a constant expression}}
}
}