http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53927
--- Comment #6 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2013-01-31 22:34:02 UTC --- > The idea is you can determine which instance by computing the static link, > then unwind the stack and look for the corresponding CFA. > The test case here is supposed to confound simplistic approaches to this > by having multiple instances of 'nestee' on the stack. Yes, but you can do something useful even with this value of DW_AT_static_link, albeit not exactly what DWARF means. In the GDB released by AdaCore, we do use this value of DW_AT_static_link to deal with up-level references; you can ask Joel for the details. > Note also that if the nested function doesn't refer to any variables from > the outer scope, then GCC seems not to emit DW_AT_static_link at all. > I guess this is an optimization; but it is a little unfortunate since > it makes debugging less obvious. Indeed, that's why in AdaCore's version of the compiler, we always generate DW_AT_static_link at -O0, and we even force the static chain onto the stack in this case (as there are no location lists at -O0).
