[Bug other/15000] Support setting the default symbol visibility for ELF

[s_gccbugzilla at nedprod dot com]

------- Additional Comments From s_gccbugzilla at nedprod dot com  2004-05-05 20:38 -------
> The old patch also works "inside outwards".

You're absolutely right. However I had hoped that because we get called at more 
opportunities than the new patch I could find some method. However, at the end 
of work last night I came to the realisation that the same method will be needed 
by other, therefore the newer is to be preferred.

> One reason for that, I think, is that attributes can come at the end of a
> declaration, like this example from the documentation:

My reading of this actually is that GCC needs to know the sizeof() things before 
it does much else. To know the size of a class requires parsing it from the most 
nested class outwards. I don't think this can be changed.

> it would not be possible to know the outer class visibility when processing
> foo::bar.

Agreed.

> 1. Say that the visibility attribute can only be at the beginning of a
> class/struct declaration, and arrange to handle that attribute _before_ we 
begin
> parsing class members.  I don't think there is any existing mechanism for
> handling attributes at this stage, so we'd have to create something new.
> 
> 2. Recursively reset DECL_VISIBILITY for members of inner classes once we 
reach
> the end of a top-level class definition.

Out of these two, the second seems to me the less work and the least intrusive. 
I tried the second last night, but there's a problem - the bit which parses and 
applies the attributes lives in C land which of course knows nothing about C++ 
and so can't have the class stack available (which makes things much easier). I 
tried an extern function, but I think they live in different binaries anyway so 
no good.

This means the only realistic solution is for handle_visibility_attribute() to 
see if it's being applied to a class/struct and if so, to traverse all children 
nodes to see if they are class/struct and if and only if they haven't had a 
visibility specified for them, overwrite that with the enclosing class 
visibility. For this we'll need visibility_specified back in the decl structure 
I think as I couldn't get C land to work with attributes in the TYPE_NAME(tree) 
when within handle_visibility_attribute(). But then I am very much out of my 
depth - I really am not sure of the mechanics underneath :(

BTW I have your pragma working fine, you can push and pop state from an internal 
stack too. I'll make a patch based on your new one with everything except nested 
class visibility setting and post it here, hopefully tonight.

Cheers,
Niall


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15000