r175326 - Rework the visibility computation algorithm in preparation

[John McCall]

On Feb 26, 2013, at 8:39 AM, Rafael Espíndola <rafael.espindola at gmail.com> wrote:
>> I found one more bug, with problem (1). It looks like the first
>> declaration of a type must be marked visible, not just any declaration
>> before an instantiation with that type:
> 
> The problem comes from the template using the canonical (first) decl
> for the arguments. Some extra examples:
> 
> template <typename T>
> struct __attribute__((visibility("default"))) barT {
>  static void zed() {}
> };
> class foo;
> class __attribute__((visibility("default"))) foo;
> template struct barT<foo>;
> 
> template <int* I>
> struct __attribute__((visibility("default"))) barI {
>  static void zed() {}
> };
> extern int I;
> extern int I __attribute__((visibility("default")));
> template struct barI<&I>;
> 
> typedef void (*fType)(void);
> template<fType F>
> struct __attribute__((visibility("default"))) barF {
>  static void zed() {}
> };
> void F();
> void F() __attribute__((visibility("default")));;
> template struct barF<F>;
> 
> This is somewhat easy to hack in the visibility computation (see
> attached patch), but what should we do for cases like:
> 
> 
> template <typename T>
> struct __attribute__((visibility("default"))) barT {
>  static void zed() {}
> };
> class foo;
> template struct barT<foo>;
> class __attribute__((visibility("default"))) foo;
> 
> 
> With this patch we print a hidden visibility. But for
> 
> emplate <int* I>
> struct __attribute__((visibility("default"))) barI {
>  static void zed() {}
> };
> extern int I;
> void use() {
>  barI<&I>::zed();
> }
> extern int I __attribute__((visibility("default")));
> 
> We produce a default one unless the last line is commented. Should the
> template instantiation point to the last decl available when it is
> created?

In these cases, templates point to types, not declarations.
But the declaration stored in the type is the first declaration until
we see a definition, at which point it's always that.

This patch seems fine.

John.