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[clang][bytecode] Handle reads on zero-size arrays #152706

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Merged
merged 1 commit into from
Aug 8, 2025
Merged

[clang][bytecode] Handle reads on zero-size arrays #152706

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4 changes: 1 addition & 3 deletions clang/lib/AST/ByteCode/Interp.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -518,7 +518,7 @@ bool CheckNull(InterpState &S, CodePtr OpPC, const Pointer &Ptr,

bool CheckRange(InterpState &S, CodePtr OpPC, const Pointer &Ptr,
AccessKinds AK) {
if (!Ptr.isOnePastEnd())
if (!Ptr.isOnePastEnd() && !Ptr.isZeroSizeArray())
return true;
if (S.getLangOpts().CPlusPlus) {
const SourceInfo &Loc = S.Current->getSource(OpPC);
Expand Down Expand Up @@ -829,8 +829,6 @@ bool CheckFinalLoad(InterpState &S, CodePtr OpPC, const Pointer &Ptr) {
return false;
if (!CheckExtern(S, OpPC, Ptr))
return false;
if (!CheckRange(S, OpPC, Ptr, AK_Read))
return false;
if (!CheckActive(S, OpPC, Ptr, AK_Read))
return false;
if (!CheckLifetime(S, OpPC, Ptr.getLifetime(), AK_Read))
Expand Down
17 changes: 17 additions & 0 deletions clang/test/AST/ByteCode/arrays.cpp
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Expand Up @@ -779,3 +779,20 @@ namespace DiscardedSubScriptExpr {
return true;
}
}

namespace ZeroSizeArrayRead {
constexpr char str[0] = {};
constexpr unsigned checksum(const char *s) {
unsigned result = 0;
for (const char *p = s; *p != '\0'; ++p) { // both-note {{read of dereferenced one-past-the-end pointer}}
result += *p;
}
return result;
}
constexpr unsigned C = checksum(str); // both-error {{must be initialized by a constant expression}} \
// both-note {{in call to}}

constexpr const char *p1 = &str[0];
constexpr const char *p2 = &str[1]; // both-error {{must be initialized by a constant expression}} \
// both-note {{cannot refer to element 1 of array of 0 elements in a constant expression}}
}