Wed May 1 23:02:00 GMT 2019
On Wed, May 01, 2019 at 05:08:15PM +0000, Sasha Da Rocha Pinheiro wrote:
> yes, I did use dwarf_frame_register(), I believe I mentioned that :).
Sorry, I missed that.
> In the case I brought up you're saying it was an elfutils' libdw
> decision to provide negative number as DW_OP_plus_uconst (unsigned
> constant)? So there would be no harm to cast it to a signed int??
Yes, since I don't believe there is a better representation.
There is no DW_OP_plus_sconst for example.
> Do you know if the rules to find the registers will always have only
> another one register associated to it? Because libdwarf function
> dwarf_get_fde_info_for_reg3() returns a register_num, which is
> described as: "Argument register_num should point to a location
> which will hold the register number associated with the register
I am not familiar with libdwarf, so don't know how to answer this question
> elfutils only gives us a location description in an array of
> Dwarf_Op. Does it provide methods to "execute" it so we can get the
> result of the expressions? Or it delegates it to the consumer?
It doesn't have a generic location description "executor". It really
should have. But to make it generic it needs a lot of context.
libdwfl does contain a partial operator interpreter for unwinding. See
expr_eval in libdwfl/frame_unwind.c. To turn that into something more
generic we would need some way to provide it with things like memory
accessors and register values. libdwfl provides some of that through
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