Re: Ada testsuite failures

[Joel Brobecker <brobecker at adacore dot com>]

> (gdb) ptype bar.empty
> No definition of "bar.empty" in current context.

Thanks for sending me your objfiles. I know what's going on, now.
Once I understood the source of this issue, it was actually fairly
simple to reproduce the problem with a C program. Consider:

    struct empty {};
    struct not_empty { long long a; };
    
    int
    main (void)
    {
      struct empty e = {};
      struct not_empty n = { 1 };
    
      n.a = (long long) &e;
    
      return 0;
    }

The heart of the problem is that struct empty is a struct that does
not have any children. We have some guards in dwarf2read.c for both
partial symbols and full symbols readers that make GDB ignore the
DW_TAG_structure DIEs for type empty:

    add_partial_symbol (...)
    {
        case DW_TAG_structure_type:
          /* Skip aggregate types without children, these are external
             references.  */
          /* NOTE: carlton/2003-10-07: See comment in new_symbol about
             static vs. global.  */
 !!!->    if (pdi->has_children == 0)
            return;
          add_psymbol_to_list (actual_name, strlen (actual_name),

Same for full symbols:

    process_structure_scope (...)
    {
    [...]
      if (die->child != NULL && ! die_is_declaration (die, cu))
        new_symbol (die, die->type, cu);

What saves us with our version of GNAT Pro is that the compiler
also creates a DW_TAG_typedef DIE associated to this struct.
This is this DIE that allows GDB to create a symbol for this type.

With the C example above, where the language allows me to control
whether typedefs are emitted or not, I can reproduce with the compiler
I use the same problem as yours.

The guards cited above have been there since version 1.1 of dwarf2read.c.
I don't know how relevant they are now - presumably today's compilers
would rather use a declaration attribute rather than empty structs.
Strictly speaking, the guard as implemented is wrong. So I propose to
simply remove it.

2006-02-03  Joel Brobecker  <brobecker@adacore.com>

        * dwarf2read.c (add_partial_symbol): Update copyright year.
        Do not skip struct, union and enum types with no children.

2006-02-03  Joel Brobecker  <brobecker@adacore.com>

        * gdb.base/nofield.c: New file.
        * gdb.base/nofield.exp: New testcase.

Tested on x86_64-linux. No regression. Nofield.exp has two FAILs before
the patch, and is all PASS after.

OK to apply?

(It should fix the problem you are seeing, but I am unable to verify
this, because I can't run your program on my machine. It was compiled
with the shared version of the GNAT runtime (libgnat-4.0.so). Next
time I'll make sure to ask to add -bargs -static. Can you verify that
your FAIL is gone with this patch? - Thank you!)

-- 
Joel

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