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constexpr: initialization of a union from an empty initializer-list should 

zero-initialize the first union member. Also fix a bug where initializing an
array of types compatible with wchar_t from a wide string literal failed in C,
and fortify the C++ tests in this area. This part can't be tested without a code
change to enable array evaluation in C (where an existing test fails).

llvm-svn: 148035
This commit is contained in:
Richard Smith 2012-01-12 18:54:33 +00:00
parent 0014e38a8b
commit 9eae723c18
3 changed files with 49 additions and 8 deletions
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31
clang/lib/AST/ExprConstant.cpp
View File

@ -3015,14 +3015,20 @@ bool RecordExprEvaluator::VisitInitListExpr(const InitListExpr *E) {
const ASTRecordLayout &Layout = Info.Ctx.getASTRecordLayout(RD);
if (RD->isUnion()) {
Result = APValue(E->getInitializedFieldInUnion());
if (!E->getNumInits())
const FieldDecl *Field = E->getInitializedFieldInUnion();
Result = APValue(Field);
if (!Field)
return true;
// If the initializer list for a union does not contain any elements, the
// first element of the union is value-initialized.
ImplicitValueInitExpr VIE(Field->getType());
const Expr *InitExpr = E->getNumInits() ? E->getInit(0) : &VIE;
LValue Subobject = This;
HandleLValueMember(Info, E->getInit(0), Subobject,
E->getInitializedFieldInUnion(), &Layout);
HandleLValueMember(Info, InitExpr, Subobject, Field, &Layout);
return EvaluateConstantExpression(Result.getUnionValue(), Info,
Subobject, E->getInit(0));
Subobject, InitExpr);
}
assert((!isa<CXXRecordDecl>(RD) || !cast<CXXRecordDecl>(RD)->getNumBases()) &&
@ -3065,6 +3071,10 @@ bool RecordExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E) {
const CXXConstructorDecl *FD = E->getConstructor();
bool ZeroInit = E->requiresZeroInitialization();
if (CheckTrivialDefaultConstructor(Info, E->getExprLoc(), FD, ZeroInit)) {
// If we've already performed zero-initialization, we're already done.
if (!Result.isUninit())
return true;
if (ZeroInit)
return ZeroInitialization(E);
@ -3391,7 +3401,7 @@ bool ArrayExprEvaluator::VisitInitListExpr(const InitListExpr *E) {
// C++11 [dcl.init.string]p1: A char array [...] can be initialized by [...]
// an appropriately-typed string literal enclosed in braces.
if (E->getNumInits() == 1 && CAT->getElementType()->isAnyCharacterType() &&
if (E->getNumInits() == 1 && E->getInit(0)->isGLValue() &&
Info.Ctx.hasSameUnqualifiedType(E->getType(), E->getInit(0)->getType())) {
LValue LV;
if (!EvaluateLValue(E->getInit(0), LV, Info))
@ -3446,7 +3456,9 @@ bool ArrayExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E) {
if (!CAT)
return Error(E);
Result = APValue(APValue::UninitArray(), 0, CAT->getSize().getZExtValue());
bool HadZeroInit = !Result.isUninit();
if (!HadZeroInit)
Result = APValue(APValue::UninitArray(), 0, CAT->getSize().getZExtValue());
if (!Result.hasArrayFiller())
return true;
@ -3454,6 +3466,9 @@ bool ArrayExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E) {
bool ZeroInit = E->requiresZeroInitialization();
if (CheckTrivialDefaultConstructor(Info, E->getExprLoc(), FD, ZeroInit)) {
if (HadZeroInit)
return true;
if (ZeroInit) {
LValue Subobject = This;
Subobject.addArray(Info, E, CAT);
@ -3485,7 +3500,7 @@ bool ArrayExprEvaluator::VisitCXXConstructExpr(const CXXConstructExpr *E) {
LValue Subobject = This;
Subobject.addArray(Info, E, CAT);
if (ZeroInit) {
if (ZeroInit && !HadZeroInit) {
ImplicitValueInitExpr VIE(CAT->getElementType());
if (!EvaluateConstantExpression(Result.getArrayFiller(), Info, Subobject,
&VIE))

12
clang/test/CXX/dcl.decl/dcl.init/dcl.init.string/p1.cpp
View File

@ -5,3 +5,15 @@ extern char x1[6];
char x2[] = "hello";
extern char x2[6];
char x3[] = { "hello" };
extern char x3[6];
wchar_t x4[](L"hello");
extern wchar_t x4[6];
wchar_t x5[] = L"hello";
extern wchar_t x5[6];
wchar_t x6[] = { L"hello" };
extern wchar_t x6[6];

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

@ -357,6 +357,8 @@ constexpr int MangleChars(const Char *p) {
}
static_assert(MangleChars("constexpr!") == 1768383, "");
static_assert(MangleChars(u8"constexpr!") == 1768383, "");
static_assert(MangleChars(L"constexpr!") == 1768383, "");
static_assert(MangleChars(u"constexpr!") == 1768383, "");
static_assert(MangleChars(U"constexpr!") == 1768383, "");
@ -404,6 +406,12 @@ static_assert(t.c[4] == 0, "");
static_assert(t.c[5] == 0, "");
static_assert(t.c[6] == 0, ""); // expected-error {{constant expression}} expected-note {{one-past-the-end}}
struct U {
wchar_t chars[6];
int n;
} constexpr u = { { L"test" }, 0 };
static_assert(u.chars[2] == L's', "");
}
namespace Array {
@ -726,6 +734,12 @@ static_assert((&u[1].b)[1] == 2, ""); // expected-error {{constant expression}}
static_assert(*(&(u[1].b) + 1 + 1) == 3, ""); // expected-error {{constant expression}} expected-note {{cannot refer to element 2 of non-array object}}
static_assert((&(u[1]) + 1 + 1)->b == 3, "");
constexpr U v = {};
static_assert(v.a == 0, "");
union Empty {};
constexpr Empty e = {};
// Make sure we handle trivial copy constructors for unions.
constexpr U x = {42};
constexpr U y = x;