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, 37 insertions, 4 deletions

diff --git a/debug.c b/debug.c
index f2cacfe5..26a2572b 100644
--- a/debug.c
+++ b/debug.c
@@ -38,17 +38,50 @@
 #include "unwind.h"
 #include "stream.h"
 #include "parser.h"
+#include "struct.h"
 #include "eval.h"
+#include "arith.h"
 #include "txr.h"
 #include "debug.h"
 
 int opt_debugger;
-int debug_state;
+unsigned debug_state;
 
-#if __STDC_VERSION__ >= 199901L
-int debug_set_state(int state);
-#endif
+static val sys_print_backtrace_s;
+
+static val dbg_clear(val mask)
+{
+  return unum(debug_clear(c_unum(mask)));
+}
+
+static val dbg_set(val mask)
+{
+  return unum(debug_set(c_unum(mask)));
+}
+
+static val dbg_restore(val state)
+{
+  debug_restore(c_unum(state));
+  return nil;
+}
 
 void debug_init(void)
 {
+  sys_print_backtrace_s = intern(lit("print-backtrace"), system_package);
+  reg_varl(intern(lit("dbg-enable"), system_package), num_fast(DBG_ENABLE));
+  reg_varl(intern(lit("dbg-step"), system_package), num_fast(DBG_STEP));
+  reg_varl(intern(lit("dbg-backtrace"), system_package), num_fast(DBG_BACKTRACE));
+  reg_varl(intern(lit("dbg-all"), system_package), num_fast(DBG_ALL));
+  reg_fun(intern(lit("dbg-clear"), system_package), func_n1(dbg_clear));
+  reg_fun(intern(lit("dbg-set"), system_package), func_n1(dbg_set));
+  reg_fun(intern(lit("dbg-restore"), system_package), func_n1(dbg_restore));
+}
+
+void debug_dump_backtrace(val stream, val prefix)
+{
+  val fb = lookup_fun(nil, sys_print_backtrace_s);
+  if (fb)
+    funcall2(cdr(fb), stream, prefix);
+  else
+    format(nil, lit("~s: no function binding"), sys_print_backtrace_s, nao);
 }