https://sourceware.org/bugzilla/show_bug.cgi?id=30085
--- Comment #2 from Mark Wielaard <mark at klomp dot org> ---
I asked around and John DelSignore came up with the following fortran example:
= array.f95 =
program f_prog
integer*4, allocatable, target, dimension (:,:) :: big_array
integer, dimension (:,:), pointer :: neg_array
allocate (big_array(2000,1000))
neg_array => big_array(2000:1:-1,1000:1:-1)
end program f_prog
So, neg_array is a pointer to an array section where the elements of big_array
are reversed. That is, neg_array(x,y) references big_array(2000-x+1,1000-y+1).
In this example, the stride makes us go "backwards" into the array.
But note that gfortran -g array.f95 produces DW_FORM_exprlocs for the
DW_AT_byte_stride because almost all attributes of the array are dynamic at
runtime:
[ c9] array_type abbrev: 10
ordering (data1) col_major (1)
data_location (exprloc)
[ 0] push_object_address
[ 1] deref
allocated (exprloc)
[ 0] push_object_address
[ 1] deref
[ 2] lit0
[ 3] ne
type (ref4) [ 72]
sibling (ref4) [ 106]
[ db] subrange_type abbrev: 1
lower_bound (exprloc)
[ 0] push_object_address
[ 1] plus_uconst 48
[ 3] deref
upper_bound (exprloc)
[ 0] push_object_address
[ 1] plus_uconst 56
[ 3] deref
byte_stride (exprloc)
[ 0] push_object_address
[ 1] plus_uconst 40
[ 3] deref
[ 4] push_object_address
[ 5] plus_uconst 32
[ 7] deref
[ 8] mul
[ f0] subrange_type abbrev: 1
lower_bound (exprloc)
[ 0] push_object_address
[ 1] plus_uconst 72
[ 3] deref
upper_bound (exprloc)
[ 0] push_object_address
[ 1] plus_uconst 80
[ 3] deref
byte_stride (exprloc)
[ 0] push_object_address
[ 1] plus_uconst 64
[ 3] deref
[ 4] push_object_address
[ 5] plus_uconst 32
[ 7] deref
[ 8] mul
[ 106] array_type abbrev: 11
ordering (data1) col_major (1)
data_location (exprloc)
[ 0] push_object_address
[ 1] deref
associated (exprloc)
[ 0] push_object_address
[ 1] deref
[ 2] lit0
[ 3] ne
type (ref4) [ 72]
[ 114] subrange_type abbrev: 1
lower_bound (exprloc)
[ 0] push_object_address
[ 1] plus_uconst 48
[ 3] deref
upper_bound (exprloc)
[ 0] push_object_address
[ 1] plus_uconst 56
[ 3] deref
byte_stride (exprloc)
[ 0] push_object_address
[ 1] plus_uconst 40
[ 3] deref
[ 4] push_object_address
[ 5] plus_uconst 32
[ 7] deref
[ 8] mul
[ 129] subrange_type abbrev: 1
lower_bound (exprloc)
[ 0] push_object_address
[ 1] plus_uconst 72
[ 3] deref
upper_bound (exprloc)
[ 0] push_object_address
[ 1] plus_uconst 80
[ 3] deref
byte_stride (exprloc)
[ 0] push_object_address
[ 1] plus_uconst 64
[ 3] deref
[ 4] push_object_address
[ 5] plus_uconst 32
[ 7] deref
[ 8] mul
Something dwarf_aggregate_size doesn't handle. And even if it could handle the
expression, it doesn't know the object address or how to deref memory...
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