debugger: initial backtrace support.

* debug.c (debug_state): Switch to unsigned, since this is now
a bitmask.
(sys_print_backtrace_s): New symbol variable.
(dbg_clear, dbg_set, dbg_restore): New static functions.
(debug_init): Initialize sys_print_backtrace_s. Register
dbg-clear, dbg-set, dbg-restore intrinsics. Register
dbg-enable, dbg-step, dbg-backtrace and dbg-all bitmask
variables, Lisp equivalents of DBG_ENABLE, DBG_SETP,
DBG_BACKTRACE and DBG_ALL.
(debug_dump_backtrace): New function.

* debug.h (opt_debugger): Declaration removed.
(debug_state): Declaration updated.
(DBG_ENABLE, DBG_STEP, DBG_BACKTRACE, DBG_ALL): New
preprocessor symbols.
(debug_set_state): Inline function removed.
(debug_clear, debug_set, debug_restore): New inline functions.
(dbg_backtrace, dbg_fcall_begin, dbg_fcall_end): New macros.
(debug_dump_backtrace): Declared.

* eval.c (error_trace): Invoke debug_dump_backtrace if support
is compiled in and backtraces are enabled.

* lib.c (do_generic_funcall): New function, copy of
generic_funcall.
(generic_funcall): Now a wrapper for do_generic_funcall which
registers fcall frames if backtrace support is enabled.
(funcall, funcall1, funcall2, funcall3, funcall4): Route to
slow generic_funcall path if backtraces are enabled.

* lisplib.c (debugger_instantiate, debugger_set_entries):
New static functions.
(lisplib_init): Autload support for debug module via above
new functions.
(lisplib_try_load): Save and restore debugger state in new
way using debug_set and debug_restore, with specific mask
values.

* parser.y (parse_once): Disable debugging in new way.

* share/txr/stdlib/debug.tl New file.

* sighal.h (EJ_DBG_MEMB, EJ_DBG_SAVE, EJ_DBG_REST): New
macros for saving/restoring debug state.
(EJ_OPT_MEMB, EJ_OPT_SAVE, EJ_OPT_REST): Reference the above
macros to include debug state in extended jump context.

* txr.c (help): Document --backtrace and that that -d
implies --backtrace.
(txr_main): Enable debugger using debug_set.
Provide new --backtrace option to enable backtraces only.

* unwind.c (args_s): New symbol variable.
(fcall_frame_type): New static variable.
(unwind_to_exit_point): Save pointer to original frame stack
and restore it when calling error_trace.  This is so that
error_trace can walk the stack to collect a backtrace.
(uw_find_frames_by_mask, uw_push_fcall): New functions.
(uw_late_init): Initialize args_s and fcall_frame_type.
gc-protect fcall_frame_type. Register uw-* variables
corresponding to the UW_* frame types.

* unwind.h (uw_frtype_t): New enum constant UW_FCALL.
(struct uw_fcall): New frame structure.
(union uw_frame): New member fc.
(uw_push_fcall, uw_find_frames_by_mask): Declared.

1 files changed, 47 insertions, 6 deletions

diff --git a/debug.h b/debug.h
index 61ce6a6f..4eb042e2 100644
--- a/debug.h
+++ b/debug.h
@@ -25,24 +25,65 @@
  * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  */
 
-extern int opt_debugger;
 
-int debug_state;
+#define DBG_ENABLE      1
+#define DBG_STEP        2
+#define DBG_BACKTRACE   4
+#define DBG_ALL         7
 
 #if CONFIG_DEBUG_SUPPORT
 
+extern unsigned debug_state;
+
 void debug_init(void);
 
-INLINE int debug_set_state(int state)
+INLINE unsigned debug_clear(unsigned mask)
 {
   int ret = debug_state;
-  debug_state = state;
+  debug_state &= ~mask;
   return ret;
 }
 
+INLINE unsigned debug_set(unsigned mask)
+{
+  int ret = debug_state;
+  debug_state |= mask;
+  return ret;
+}
+
+INLINE void debug_restore(unsigned state)
+{
+  debug_state = state;
+}
+
+void debug_dump_backtrace(val stream, val prefix);
+
+#define dbg_backtrace (debug_state & DBG_BACKTRACE)
+
+#define dbg_fcall_begin(fun, args)      \
+  {                                     \
+    uw_frame_t uw_fc;                   \
+    args_decl(args_cp, args->argc);     \
+    args_copy(args_cp, args);           \
+    uw_push_fcall(&uw_fc, fun, args_cp)
+
+#define dbg_fcall_end                   \
+    uw_pop_frame(&uw_fc);               \
+  }
+
 #else
 
-#define debug_init() ((void) 0)
-#define debug_set_state(S) 0
+#define debug_clear(mask) 0
+#define debug_set(mask) 0
+#define debug_restore(state) ((void) 0)
+#define debug_dump_backtrace(stream, prefix) ((void) 0)
+
+#define dbg_backtrace 0
+
+#define dbg_fcall_begin(fun, args)      \
+  {
+
+#define dbg_fcall_end                   \
+  }
 
 #endif