frame-instruction-pointer is absolute; rewrite (system vm coverage)
* libguile/frames.c (scm_frame_source): Instead of assuming that
scm_frame_procedure is correct, use the IP to get the source.
(scm_frame_instruction_pointer): Return an absolute value instead of
assuming that slot 0 is correct. (It isn't, when preparing for a tail
call.)
* libguile/programs.h:
* libguile/programs.c (scm_find_source_for_addr): New internal helper.
* module/system/repl/debug.scm (print-registers): Readably print
absolute instruction pointers.
* module/system/vm/coverage.scm: Complete rewrite to use absolute IP's.
We can't assume that frame-procedure is cheap if it is correct, or
correct if it is cheap. Anyway using the address is better anyway.
(coverage-data->lcov): Disable per-function info temporarily.
(loaded-modules, module-procedures, closest-source-line)
(closed-over-procedures): Remove these. Instead of going from
procedures to source info, now we go from ELF image to source info.
* module/system/vm/debug.scm (debug-context-length): New interface.
* module/system/vm/program.scm (source-for-addr): New internal helper.