[Bug gdb/28480] pretty printing getting confused

["simark at simark dot ca" <sourceware-bugzilla@sourceware.org>]

https://sourceware.org/bugzilla/show_bug.cgi?id=28480

--- Comment #14 from Simon Marchi <simark at simark dot ca> ---
(In reply to Jonathan Wakely from comment #12)
> Aha, the std::tuple case is more like this:
> 
> struct X
> {
>   int i = 0x1;
> };
> 
> struct Y
> {
>   struct S { };
>   [[no_unique_address]] S i;
> };
> 
> struct XX : X { };
> 
> struct Z : Y, XX { };
> 
> int main()
> {
>   Z z;
>   return 0;
> }

I think you can get rid of XX (make Z directly inherit from X) and it still
reproduces.

> 
> Here z.i is ambiguous, but GDB doesn't diagnose it.
> 
> And GDB 10 returns z.X::i but GDB 11 returns z.Y::i

If I try to use z.i in the program, it doesn't compile:

test.cpp: In function ‘int main()’:
test.cpp:17:12: error: request for member ‘i’ is ambiguous
   17 |   return z.i;
      |            ^
test.cpp:3:7: note: candidates are: ‘int X::i’
    3 |   int i = 0x1;
      |       ^
test.cpp:9:27: note:                 ‘Y::S Y::i’
    9 |   [[no_unique_address]] S i;
      |                           ^

So I agree, it makes sense for GDB to not accept the expression.  It looks like
the intent is to reject and (and print the "request is ambiguous" message), but
that the no_unique_address tag confuses GDB.

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