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[clang][ExprConst] Don't diagnose a non-existent init as not constant #124575

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Jan 28, 2025
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[clang][ExprConst] Don't diagnose a non-existent init as not constant #124575

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c0cee82
[clang][ExprConst] Don't diagnose a non-existent init as not constant
tbaederr Jan 27, 2025
5d99160
Use existing Init variable
tbaederr Jan 28, 2025
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8 changes: 6 additions & 2 deletions clang/lib/AST/ExprConstant.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -3600,8 +3600,12 @@ static bool evaluateVarDeclInit(EvalInfo &Info, const Expr *E,
VD->mightBeUsableInConstantExpressions(Info.Ctx)) ||
((Info.getLangOpts().CPlusPlus || Info.getLangOpts().OpenCL) &&
!Info.getLangOpts().CPlusPlus11 && !VD->hasICEInitializer(Info.Ctx))) {
Info.CCEDiag(E, diag::note_constexpr_var_init_non_constant, 1) << VD;
NoteLValueLocation(Info, Base);
if (Init) {
Info.CCEDiag(E, diag::note_constexpr_var_init_non_constant, 1) << VD;
NoteLValueLocation(Info, Base);
} else {
Info.CCEDiag(E);
}
}

// Never use the initializer of a weak variable, not even for constant
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8 changes: 4 additions & 4 deletions clang/test/SemaCXX/constant-expression-cxx11.cpp
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Expand Up @@ -1462,7 +1462,7 @@ namespace InstantiateCaseStmt {

namespace ConvertedConstantExpr {
extern int &m;
extern int &n; // expected-note 2{{declared here}}
extern int &n; // pre-cxx23-note 2{{declared here}}

constexpr int k = 4;
int &m = const_cast<int&>(k);
Expand All @@ -1471,9 +1471,9 @@ namespace ConvertedConstantExpr {
// useless note and instead just point to the non-constant subexpression.
enum class E {
em = m,
en = n, // cxx23-note {{initializer of 'n' is not a constant expression}} expected-error {{enumerator value is not a constant expression}} cxx11_20-note {{initializer of 'n' is unknown}}
eo = (m + // expected-error {{not a constant expression}}
n // cxx23-note {{initializer of 'n' is not a constant expression}} cxx11_20-note {{initializer of 'n' is unknown}}
en = n, // expected-error {{enumerator value is not a constant expression}} cxx11_20-note {{initializer of 'n' is unknown}}
eo = (m + // pre-cxx23-error {{not a constant expression}}
n // cxx11_20-note {{initializer of 'n' is unknown}} cxx23-error {{not a constant expression}}
),
eq = reinterpret_cast<long>((int*)0) // expected-error {{not a constant expression}} expected-note {{reinterpret_cast}}
};
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3 changes: 1 addition & 2 deletions clang/test/SemaCXX/constant-expression-p2280r4.cpp
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Expand Up @@ -47,11 +47,10 @@ void splash(Swim& swam) {
}

extern Swim dc;
extern Swim& trident; // expected-note {{declared here}}
extern Swim& trident;

constexpr auto& sandeno = typeid(dc); // ok: can only be typeid(Swim)
constexpr auto& gallagher = typeid(trident); // expected-error {{constexpr variable 'gallagher' must be initialized by a constant expression}}
// expected-note@-1 {{initializer of 'trident' is not a constant expression}}

namespace explicitThis {
struct C {
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