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 > rule." 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 dwfl_attach_state. Cheers, Mark
