[RFA/commit] GDB hangs when printing null multi-dimensional array

[Joel Brobecker <brobecker at adacore dot com>]

Hello,

We noticed that GDB was hanging when printing multi-dimensional arrays
were one of the dimensions is null.  You would think that this case
makes little sense, and that's probably why we hadn't heard of it
until now. But an array of empty strings made us aware of the issue...

This has been reduced to:

   type Matrix is array (1 .. 10, 1 .. 0) of Character;
   type Wrapper is record
      M : Matrix;
   end record;
   My_Matrix : Wrapper := (M => (others => (others => 'a')));

If you try to print My_Matrix, GDB hangs.

The problem is that we were doing a division by zero when trying
to compute the number of elements in our array in val_print_array_elements:

   len = TYPE_LENGTH (type) / eltlen;

This is because val_print_array_elements wasn't prepared to deal with
arrays of zero-size elements.

2008-05-16  Joel Brobecker  <brobecker@adacore.com>

        * valprint.h (get_array_bounds): Renames get_array_low_bound.
        * valprint.c (get_array_bounds): Renames get_array_low_bound.
        Return the proper bound value if the array index type is an
        enumerated type. Compute the high bound if requested.
        (val_print_array_elements): Handle the case when the array
        element has a null size.
        * ada-valprint.c (print_optional_low_bound): Add handling
        for empty arrays or arrays of zero-size elements.
        (ada_val_print_array): New function, extracted out from
        ada_val_print_1 case TYPE_CODE_ARRAY, and enhanced to
        handle empty arrays and arrays of zero-size elements.
        (ada_val_print_1)[case TYPE_CODE_ARRAY]: Replace extracted-out
        code by call to ada_val_print_array.
        (ada_value_print): Remove handling of null array.  The handling
        was incomplete and is now better handled by ada_val_print_array.

2008-05-16  Joel Brobecker  <brobecker@adacore.com>

        * gdb.ada/null_array/foo.adb: Add multi-dimensional array
        of zero-size elements.
        * gdb.ada/null_array.exp: Test printing this new array.

Tested on x86-linux. I will commit in a week unless someone has
some comments on the patch.

-- 
Joel

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