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Fix rejects-valid on constexpr function that accesses a not-yet-defined 'extern 

const' variable. That variable might be defined as 'constexpr', so we cannot
prove that a use of it could never be a constant expression.

llvm-svn: 270774
This commit is contained in:
Richard Smith 2016-05-25 22:06:25 +00:00
parent dca7651d59
commit c0d04a2567
2 changed files with 22 additions and 3 deletions
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11
clang/lib/AST/ExprConstant.cpp
View File

@ -2706,7 +2706,11 @@ static CompleteObject findCompleteObject(EvalInfo &Info, const Expr *E,
}
} else {
// FIXME: Allow folding of values of any literal type in all languages.
if (Info.getLangOpts().CPlusPlus11) {
if (Info.checkingPotentialConstantExpression() &&
VD->getType().isConstQualified() && !VD->hasDefinition(Info.Ctx)) {
// The definition of this variable could be constexpr. We can't
// access it right now, but may be able to in future.
} else if (Info.getLangOpts().CPlusPlus11) {
Info.Diag(E, diag::note_constexpr_ltor_non_constexpr, 1) << VD;
Info.Note(VD->getLocation(), diag::note_declared_at);
} else {
@ -5456,8 +5460,9 @@ bool RecordExprEvaluator::VisitInitListExpr(const InitListExpr *E) {
}
auto *CXXRD = dyn_cast<CXXRecordDecl>(RD);
Result = APValue(APValue::UninitStruct(), CXXRD ? CXXRD->getNumBases() : 0,
std::distance(RD->field_begin(), RD->field_end()));
if (Result.isUninit())
Result = APValue(APValue::UninitStruct(), CXXRD ? CXXRD->getNumBases() : 0,
std::distance(RD->field_begin(), RD->field_end()));
unsigned ElementNo = 0;
bool Success = true;

14
clang/test/SemaCXX/constant-expression-cxx11.cpp
View File

@ -1181,6 +1181,20 @@ namespace ExternConstexpr {
constexpr int j = 0;
constexpr int k; // expected-error {{default initialization of an object of const type}}
}
extern const int q;
constexpr int g() { return q; }
constexpr int q = g();
static_assert(q == 0, "zero-initialization should precede static initialization");
extern int r; // expected-note {{here}}
constexpr int h() { return r; } // expected-error {{never produces a constant}} expected-note {{read of non-const}}
struct S { int n; };
extern const S s;
constexpr int x() { return s.n; }
constexpr S s = {x()};
static_assert(s.n == 0, "zero-initialization should precede static initialization");
}
namespace ComplexConstexpr {