On Jan 12, 2008 11:14 PM, Eli Friedman <[EMAIL PROTECTED]> wrote:
> Take the following two testcases:
>
> void
> foo (void)
> {
> struct b;
> struct b* x = 0;
> struct b* y = &*x;
> }
>
> void foo2 (void)
> {
> typedef int (*arrayptr)[];
> arrayptr x = 0;
> arrayptr y = &*x;
> }
>
> Currently, clang rejects both of these.
> Here is another test:
> void foo3 (void)
> {
> void* x = 0;
> void* y = &*x;
> }
Attached is a patch which makes all of these testcases work correctly
(as far as I can tell). Essentially, this just removes the error for
a completely legal construct and fixes up the void* case to work per
C99.
-Eli
Index: Sema/SemaExpr.cpp
===================================================================
--- Sema/SemaExpr.cpp (revision 45920)
+++ Sema/SemaExpr.cpp (working copy)
@@ -1618,6 +1626,18 @@
/// Note: The usual conversions are *not* applied to the operand of the &
/// operator (C99 6.3.2.1p[2-4]), and its result is never an lvalue.
QualType Sema::CheckAddressOfOperand(Expr *op, SourceLocation OpLoc) {
+ if (getLangOptions().C99) {
+ // Implement C99-only parts of addressof rules
+ if (UnaryOperator* uOp = dyn_cast<UnaryOperator>(op)) {
+ if (uOp->getOpcode() == UnaryOperator::Deref)
+ // Per C99 6.5.3.2, the address of a deref always returns a valid
result
+ // (assuming the deref expression is valid)
+ return uOp->getSubExpr()->getType();
+ }
+ // Technically, there should be a check for array subscript
+ // expressions here, but the result of one is always an lvalue anyway
+ }
+
Decl *dcl = getPrimaryDeclaration(op);
Expr::isLvalueResult lval = op->isLvalue();
@@ -1652,17 +1672,11 @@
if (const PointerType *PT = qType->getAsPointerType()) {
QualType ptype = PT->getPointeeType();
- // C99 6.5.3.2p4. "if it points to an object,...".
- if (ptype->isIncompleteType()) { // An incomplete type is not an object
- // GCC compat: special case 'void *' (treat as extension, not error).
- if (ptype->isVoidType()) {
- Diag(OpLoc,
diag::ext_typecheck_deref_ptr_to_void,op->getSourceRange());
- } else {
- Diag(OpLoc, diag::err_typecheck_deref_incomplete_type,
- ptype.getAsString(), op->getSourceRange());
- return QualType();
- }
- }
+ // Note that per both C89 and C99, this is always legal, even
+ // if ptype is an incomplete type or void.
+ // It would be possible to warn about dereferencing a
+ // void pointer, but it's completely well-defined,
+ // and such a warning is unlikely to catch any mistakes.
return ptype;
}
Diag(OpLoc, diag::err_typecheck_indirection_requires_pointer,
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