Re: Dwarf information about a symbol

[Keith Walker <keith dot walker at arm dot com>]

At 01:26 15/10/2003 -0700, ankit thukral wrote:

> for instance,if a variable ,which is in a
> register during early stages of the program,ceases to
> be in the register (due to less usage) and is stored
> in memory,then the symbol Dwarf information should
> change from DW_OP_regx to
> DW_OP_fbreg.

Yes this can be described in DWARF-2 (and DWARF-3)

The actual location (ie. the register, memory address, etc) is described by 
a Location Expression.     This is sufficient to describe an item if it's 
location does not vary.

The ability to vary the location of an item is then described by a Location 
List.    A Location List is a list of <PC address range and associated 
Location Expression>.     Using a Location List therefore allows the 
actual  location to vary depending on the current PC value.

Support for Location Lists has only recently been implemented and made 
available in gdb 6.0

Obviously this does rely on the compiler generating the relevant Location 
List information in the first place for the debugger to use.

Keith


Keith Walker           Tel:+44 (1628) 427732
ARM Ltd, Liberty House, Moorbridge Road, Maidenhead, SL6 8LT UK

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