[Bug c/47939] Missing DW_TAG_typedef for qualified types

["joseph at codesourcery dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=47939

--- Comment #6 from joseph at codesourcery dot com <joseph at codesourcery dot com> 2011-03-01 16:52:37 UTC ---
On Tue, 1 Mar 2011, rguenth at gcc dot gnu.org wrote:

> The patch bootstrapped and tested ok.  Removing
> 
>   if (!flag_gen_aux_info && (TYPE_QUALS (element_type)))
>     type = TYPE_MAIN_VARIANT (type);
> 
> unconditionally breaks gcc.dg/array-quals-2.c (but nothing else).

The point of the logic removing qualifiers here is as described in the 
comment

  /* Now figure out the structure of the declarator proper.
     Descend through it, creating more complex types, until we reach
     the declared identifier (or NULL_TREE, in an absolute declarator).
     At each stage we maintain an unqualified version of the type
     together with any qualifiers that should be applied to it with
     c_build_qualified_type; this way, array types including
     multidimensional array types are first built up in unqualified
     form and then the qualified form is created with
     TYPE_MAIN_VARIANT pointing to the unqualified form.  */

to ensure consistency in TYPE_MAIN_VARIANT for array types; see 
<http://gcc.gnu.org/ml/gcc-patches/2005-01/msg02180.html>.

> Probably a better general approach would be to make c_build_qualified_type
> also take a desired name as argument instead of using TYPE_NAME.

In general it's a desired name for an intermediate type at some level of 
array derivation, not for the type being constructed by 
c_build_qualified_type.  I suppose you could pass both the name and the 
particular type that should have that name, or otherwise indicate the 
qualifiers and level of array nesting where the name should be used if 
possible.

If you have

typedef const int T[1];
T array[2][3];

then "const" is being applied to "int [2][3][1]", and it's the 
intermediate type "const int [1]" that you'd like to get the name T.