[cfe-dev] [PATCH] fix for bug 7857 - incomplete type as array parameter in C mode

[Francois Pichet]

>   if (T->isFunctionType()) {
>
> The getCurScope()->isFunctionPrototypeScope() check doesn't ensure that this is the type of a parameter; it only means that we're within a parameter list. For example, this would allow something like:

I am not sure what the goal of T->isFunctionType() is. At this point,
T is the type on which the array is built on. We want to check if it
is an incomplete struct not if it is a function type.

>        typedef struct X X;
>        template<typename T> struct A { };
>        void f(A<X[]>);
>
> which we don't want.

The code will only be executed while compiling C code.

>
> I am okay with the general direction of downgrading this to a warning for function declarations (not definitions), but only in the narrow case of a parameter of array type.
>

Any reason why that warning shoudn't apply to function definitions? I
did some testing and both msvc and gcc will accept an incomplete
struct array type even on a function definition parameter. As long you
don't use it in way that requires the definition.

For example you can write

typedef struct Type TYPE;
void bar(TYPE a[]);
void foo(TYPE a[])
{
    bar(a);
}

But even if we wanted to emit the warning just for function
prototypes, I don't think it is easily possible with the current
design. The check to determine that we are parsing a function
definition is only done after the whole declarator has been parsed. I
couldn't find a way to check that the prototype is part of definition
at the point where the Array type is being built.