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Accept parenthesized expressions like ((void*)0) and (void*)(0) as null pointer 

constants.

llvm-svn: 39493
This commit is contained in:
Chris Lattner 2007-05-24 01:23:49 +00:00
parent a5490953d1
commit 7eef919d82
1 changed files with 29 additions and 24 deletions
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53
clang/AST/Expr.cpp
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@ -266,32 +266,37 @@ bool Expr::isConstantExpr(bool isIntConst, SourceLocation &loc) const {
}
}
// C99 6.3.2.3p3: FIXME: If we have an integer constant expression, we need
// to *evaluate* it and test for the value 0. The current code is too
// simplistic...it only allows for the integer literal "0".
// For example, the following is valid code:
//
// void test1() { *(n ? p : (void *)(7-7)) = 1; }
//
/// isNullPointerConstant - C99 6.3.2.3p3 - Return true if this is either an
/// integer constant expression with the value zero, or if this is one that is
/// cast to void*.
bool Expr::isNullPointerConstant() const {
const IntegerLiteral *constant = 0;
switch (getStmtClass()) {
case IntegerLiteralClass:
constant = cast<IntegerLiteral>(this);
break;
case CastExprClass:
const CastExpr *cExpr = cast<CastExpr>(this);
if (const PointerType *p = dyn_cast<PointerType>(cExpr->getDestType())) {
QualType t = p->getPointeeType();
// the type needs to be "void *" (no qualifiers are permitted)
if (!t.getQualifiers() && t->isVoidType())
constant = dyn_cast<IntegerLiteral>(cExpr->getSubExpr());
// Strip off a cast to void*, if it exists.
if (const CastExpr *CE = dyn_cast<CastExpr>(this)) {
// Check that it is a cast to void*.
if (const PointerType *PT = dyn_cast<PointerType>(CE->getType())) {
QualType Pointee = PT->getPointeeType();
if (Pointee.getQualifiers() == 0 && Pointee->isVoidType() && // to void*
CE->getSubExpr()->getType()->isIntegerType()) // from int.
return CE->getSubExpr()->isNullPointerConstant();
}
break;
default:
return false;
} else if (const ParenExpr *PE = dyn_cast<ParenExpr>(this)) {
// Accept ((void*)0) as a null pointer constant, as many other
// implementations do.
return PE->getSubExpr()->isNullPointerConstant();
}
return constant && constant->getValue() == 0;
// This expression must be an integer type.
if (!getType()->isIntegerType())
return false;
// FIXME: If we have an integer constant expression, we need
// to *evaluate* it and test for the value 0. The current code is too
// simplistic...it only allows for the integer literal "0".
// For example, the following is valid code:
//
// void test1() { *(n ? p : (void *)(7-7)) = 1; }
//
if (const IntegerLiteral *C = dyn_cast<IntegerLiteral>(this))
return C->getValue() == 0;
return false;
}