Previously we only have an extension that warn void pointer deferencing
in C++, but for C we did nothing.
C2x 6.5.3.2p4 says The unary * operator denotes indirection. If it points
to an object, the result is an lvalue designating the object. However, there
is no way to form an lvalue designating an object of an incomplete type as
6.3.2.1p1 says "an lvalue is an expression (with an object type other than
void)", so the behavior is undefined.
Fixes https://github.com/llvm/llvm-project/issues/53631
Signed-off-by: Jun Zhang <jun@junz.org>
Differential Revision: https://reviews.llvm.org/D134461
- This is designed to make it obvious that %clang_cc1 is a "test variable"
which is substituted. It is '%clang_cc1' instead of '%clang -cc1' because it
can be useful to redefine what gets run as 'clang -cc1' (for example, to set
a default target).
llvm-svn: 91446
Neil, can you point me to the place in the C99 spec that says this is allowed? I thought Expr::isLvalue() conformed to the spec, which says "C99 6.3.2.1: an lvalue is an expression with an object type or an incomplete type other than void.". Please advise.
llvm-svn: 46917
Remove diagnostics from Sema::CheckIndirectionOperand(). C89/C99 allow dereferencing an incomplete type. clang appears to be emulating some incorrect gcc behavior (see below).
void
foo (void)
{
struct b;
struct b* x = 0;
struct b* y = &*x; // gcc produces an error ("dereferencing pointer to incomplete type")
}
With this patch, the above is now allowed.
Bug/Patch by Eli Friedman!
llvm-svn: 45933
Jun Zhang