On 04/08/14 01:39, Mark Wielaard wrote:
Of course it doesn't need to use a DW_AT_start_scope, it can also use a
location list, generate an extra narrower lexical block that owns the
data object DIE, or maybe not generate any of that at all. The point was
that the intention of what the valid ranges of the default entry are in
cases when such attributes are generated are clearly documented.
There is no relationship between scope and the address ranges in a
location expression or location list.
If you persist in confabulating that these interact in ways which are
not described in the DWARF specification, you will continue to make
incorrect assumptions.
One may assume that debugger developers have an understanding of the
calling sequence for a function and that they are aware that locations
which are described as being on a stack frame are not valid until the
frame is created.
It is not just when the stack frame is created but also when which stack
slots are seeded with the actual values (and a compiler using shrink
wrapping might sprinkle the frame setup and allocations throughout the
function). That is precisely why a DWARF producer can use attributes
like DW_AT_start_scope, use an lexical block with narrower scope or use
location lists to indicate over which address range a location
expression is valid. I just want to make it clear how these attributes,
when used by a producer to guide a consumer, interact with the default
entry proposal.
Scope defines where a name is known withing a program and what object
it is bound to: http://en.wikipedia.org/wiki/Scope_%28computer_science%29
There is no interaction between scope and lifetime of an object in DWARF.
--
Michael Eager ea...@eagercon.com
1960 Park Blvd., Palo Alto, CA 94306 650-325-8077
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