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[clang] Fix const eval of constexpr-unknown relational comparisons. #150088

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Merged
merged 3 commits into from
Jul 24, 2025
Merged

[clang] Fix const eval of constexpr-unknown relational comparisons. #150088

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51b5621
[clang] Fix const eval of constexpr-unknown relational comparisons.
efriedma-quic Jul 22, 2025
9a9e326
Fix test so it's actually checking constexpr-unknown.
efriedma-quic Jul 22, 2025
2715f36
Fix crash on relational comparison with null.
efriedma-quic Jul 24, 2025
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6 changes: 4 additions & 2 deletions clang/lib/AST/ExprConstant.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -14632,7 +14632,9 @@ EvaluateComparisonBinaryOperator(EvalInfo &Info, const BinaryOperator *E,
if (!LHSDesignator.Invalid && !RHSDesignator.Invalid && IsRelational) {
bool WasArrayIndex;
unsigned Mismatch = FindDesignatorMismatch(
getType(LHSValue.Base), LHSDesignator, RHSDesignator, WasArrayIndex);
LHSValue.Base.isNull() ? QualType()
: getType(LHSValue.Base).getNonReferenceType(),
LHSDesignator, RHSDesignator, WasArrayIndex);
// At the point where the designators diverge, the comparison has a
// specified value if:
// - we are comparing array indices
Expand Down Expand Up @@ -14676,7 +14678,7 @@ EvaluateComparisonBinaryOperator(EvalInfo &Info, const BinaryOperator *E,
// compare pointers within the object in question; otherwise, the result
// depends on where the object is located in memory.
if (!LHSValue.Base.isNull() && IsRelational) {
QualType BaseTy = getType(LHSValue.Base);
QualType BaseTy = getType(LHSValue.Base).getNonReferenceType();
if (BaseTy->isIncompleteType())
return Error(E);
CharUnits Size = Info.Ctx.getTypeSizeInChars(BaseTy);
Expand Down
14 changes: 14 additions & 0 deletions clang/test/SemaCXX/constant-expression-p2280r4.cpp
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Expand Up @@ -383,3 +383,17 @@ namespace enable_if_2 {
}
}
}

namespace GH150015 {
extern int (& c)[8]; // interpreter-note {{declared here}}
constexpr int x = c <= c+8; // interpreter-error {{constexpr variable 'x' must be initialized by a constant expression}} \
// interpreter-note {{initializer of 'c' is unknown}}

struct X {};
struct Y {};
struct Z : X, Y {};
extern Z &z; // interpreter-note{{declared here}}
constexpr int bases = (void*)(X*)&z <= (Y*)&z; // expected-error {{constexpr variable 'bases' must be initialized by a constant expression}} \
// nointerpreter-note {{comparison of addresses of subobjects of different base classes has unspecified value}} \
// interpreter-note {{initializer of 'z' is unknown}}
}