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[clang][bytecode] Fix CXXConstructExpr for multidim arrays #164760

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Merged
tbaederr merged 1 commit into from
Oct 24, 2025
Merged

[clang][bytecode] Fix CXXConstructExpr for multidim arrays #164760

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49 changes: 29 additions & 20 deletions clang/lib/AST/ByteCode/Compiler.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3274,34 +3274,43 @@ bool Compiler<Emitter>::VisitCXXConstructExpr(const CXXConstructExpr *E) {
}

if (T->isArrayType()) {
const ConstantArrayType *CAT =
Ctx.getASTContext().getAsConstantArrayType(E->getType());
if (!CAT)
return false;

size_t NumElems = CAT->getZExtSize();
const Function *Func = getFunction(E->getConstructor());
if (!Func)
return false;

// FIXME(perf): We're calling the constructor once per array element here,
// in the old intepreter we had a special-case for trivial constructors.
for (size_t I = 0; I != NumElems; ++I) {
if (!this->emitConstUint64(I, E))
return false;
if (!this->emitArrayElemPtrUint64(E))
return false;
if (!this->emitDupPtr(E))
return false;

// Constructor arguments.
for (const auto *Arg : E->arguments()) {
if (!this->visit(Arg))
return false;
std::function<bool(QualType)> initArrayDimension;
initArrayDimension = [&](QualType T) -> bool {
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@shafik shafik Nov 15, 2025

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Why not just initialize initArrayDimension directly?

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@tbaederr tbaederr Nov 17, 2025

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I don't thinkt that works if it calls itself.

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@shafik shafik Nov 18, 2025 •
edited
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I completely missed that aspect but that is what Deducing This is for, you pass in this auto &self.

Edit: never mind, not available in C++17 except as an extension :-(

if (!T->isArrayType()) {
// Constructor arguments.
for (const auto *Arg : E->arguments()) {
if (!this->visit(Arg))
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@shafik shafik Nov 15, 2025

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Does this if statement and it's body get tested by the tests? It does not look like it but maybe I misunderstand.

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@tbaederr tbaederr Nov 17, 2025

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The return false case is hit when direct expression evaluation fails or when we hit the size limit of the bytecode emitter. It's not tested in the here attached test case I think, but at least the expression case is tested in an existing test.

return false;
}

return this->emitCall(Func, 0, E);
}

if (!this->emitCall(Func, 0, E))
const ConstantArrayType *CAT =
Ctx.getASTContext().getAsConstantArrayType(T);
if (!CAT)
return false;
}
return true;
QualType ElemTy = CAT->getElementType();
unsigned NumElems = CAT->getZExtSize();
for (size_t I = 0; I != NumElems; ++I) {
if (!this->emitConstUint64(I, E))
return false;
if (!this->emitArrayElemPtrUint64(E))
return false;
if (!initArrayDimension(ElemTy))
return false;
}
return this->emitPopPtr(E);
};

return initArrayDimension(E->getType());
}

return false;
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11 changes: 11 additions & 0 deletions clang/test/AST/ByteCode/arrays.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -820,3 +820,14 @@ namespace FAM {
return 1;
}
}

namespace MultiDimConstructExpr {
struct a {
a *p = this;
};
struct b {
a m[3][3];
};
constexpr b d;
static_assert(d.m[2][1].p == &d.m[2][1]);
}