[PATCH] [gdb/ada] Fix assert in ada_is_unconstrained_packed_array_type

[Joel Brobecker]

Hi TomDV,

On Mon, Dec 06, 2021 at 12:31:31PM +0100, Tom de Vries wrote:
> On openSUSE Leap 42.3, with system compiler gcc 4.8.5 I run into:
> ...
> (gdb) print u_one_two_three^M
> src/gdb/gdbtypes.h:1050: internal-error: field: \
>  Assertion `idx >= 0 && idx < num_fields ()' failed.^M
> ...
> 
> We run into trouble while doing this in
> ada_is_unconstrained_packed_array_type:
> ...
> 1953          return TYPE_FIELD_BITSIZE (type, 0) > 0;
> ...
> which tries to get field 0 from a type without fields:
> ...
> (gdb) p type->num_fields ()
> $6 = 0
> ...
> which is the case because the type is a typedef:
> ...
> (gdb) p type->code ()
> $7 = TYPE_CODE_TYPEDEF
> ...
> 
> Fix this by using the type referenced by the typedef instead.
> 
> Tested on x86_64-linux.
> 
> Bug: https://sourceware.org/bugzilla/show_bug.cgi?id=28323

Thanks for the patch. This looks OK to me.

>  gdb/ada-lang.c | 2 ++
>  1 file changed, 2 insertions(+)
> 
> diff --git a/gdb/ada-lang.c b/gdb/ada-lang.c
> index f8ba05b4276..336d950ec1d 100644
> --- a/gdb/ada-lang.c
> +++ b/gdb/ada-lang.c
> @@ -1949,6 +1949,8 @@ ada_is_unconstrained_packed_array_type (struct type *type)
>        /* The structure's first field is a pointer to an array, so this
>  	 fetches the array type.  */
>        type = TYPE_TARGET_TYPE (type->field (0).type ());
> +      if (type->code () == TYPE_CODE_TYPEDEF)
> +	type = ada_typedef_target_type (type);
>        /* Now we can see if the array elements are packed.  */
>        return TYPE_FIELD_BITSIZE (type, 0) > 0;
>      }
> 
> base-commit: 2427f3b09eb23e7949878cdc0b366fb605df568f
> -- 
> 2.31.1
> 

-- 
Joel