Streamlining exception handling macros a little bit.

* eval.c (op_unwind_protect): Use uw_simple_catch_begin,
and remove the uw_catch (exsym, exvals) clause. Put
explicit braces around the unwind code even though it
is only one statement.

* match.c (do_txeval): Got rid of empty uw_unwind clause.
This is not needed any longer.
(v_try): Got rid of explicit uw_do_unwind calls.

* unwind.h (uw_simple_catch_begin): New macro.
(uw_do_unwind): Macro removed.
(uw_catch): Added goto uw_unwind_label at the front.
This way if the previous clause falls through,
control goes to the unwind logic.
(uw_unwind): Got rid of initial break. Previous
clause should fall through to unwind logic,
whether it is the main clause, or one of the catches.
(uw_catch_end): Default case aborts, because
we don't expect this.

4 files changed, 39 insertions, 13 deletions

diff --git a/ChangeLog b/ChangeLog
index c5851292..f486688c 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,29 @@
 2011-12-20  Kaz Kylheku  <kaz@kylheku.com>
 
+	Streamlining exception handling macros a little bit.
+
+	* eval.c (op_unwind_protect): Use uw_simple_catch_begin,
+	and remove the uw_catch (exsym, exvals) clause. Put
+	explicit braces around the unwind code even though it
+	is only one statement.
+
+	* match.c (do_txeval): Got rid of empty uw_unwind clause.
+	This is not needed any longer.
+	(v_try): Got rid of explicit uw_do_unwind calls. 
+
+	* unwind.h (uw_simple_catch_begin): New macro.
+	(uw_do_unwind): Macro removed.
+	(uw_catch): Added goto uw_unwind_label at the front.
+	This way if the previous clause falls through,
+	control goes to the unwind logic.
+	(uw_unwind): Got rid of initial break. Previous
+	clause should fall through to unwind logic,
+	whether it is the main clause, or one of the catches.
+	(uw_catch_end): Default case aborts, because
+	we don't expect this.
+
+2011-12-20  Kaz Kylheku  <kaz@kylheku.com>
+
 	Critical regression. Hash lookup was crashing on some platforms
 	due to negative hashing values being reduced modulo table size
 	to a negative array index.
diff --git a/eval.c b/eval.c
index f67b21af..e7475f9b 100644
--- a/eval.c
+++ b/eval.c
@@ -668,16 +668,13 @@ static val op_unwind_protect(val form, val env)
   val cleanup_forms = rest(rest(form));
   val result = nil;
 
-  uw_catch_begin(nil, exsym, exvals);
+  uw_simple_catch_begin;
 
   result = eval(prot_form, env, prot_form);
 
-  uw_do_unwind;
-
-  uw_catch (exsym, exvals);
-
-  uw_unwind
+  uw_unwind {
     eval_progn(cleanup_forms, env, cleanup_forms);
+  }
 
   uw_catch_end;
 
diff --git a/match.c b/match.c
index 09d34dec..4e060df0 100644
--- a/match.c
+++ b/match.c
@@ -1366,6 +1366,8 @@ static val do_txeval(val spec, val form, val bindings, val allow_unbound)
 
       sem_error(spec, lit("~a"), exc, nao);
     }
+
+    uw_unwind { }
   }
   uw_catch_end;
 
@@ -2748,7 +2750,6 @@ static val v_try(match_files_ctx *c)
     uw_catch_begin(catch_syms, exsym, exvals);
 
     result = match_files(mf_spec(*c, try_clause));
-    uw_do_unwind;
 
     uw_catch(exsym, exvals) {
       {
@@ -2807,7 +2808,6 @@ static val v_try(match_files_ctx *c)
           }
         }
       }
-      uw_do_unwind;
     }
 
     uw_unwind {
diff --git a/unwind.h b/unwind.h
index 4dea9469..98b965e7 100644
--- a/unwind.h
+++ b/unwind.h
@@ -133,6 +133,13 @@ noreturn val type_mismatch(val, ...);
     uw_pop_frame(&uw_env);              \
   } while (0)
 
+#define uw_simple_catch_begin           \
+  do {                                  \
+    uw_frame_t uw_catch;                \
+    uw_push_catch(&uw_catch, nil);      \
+    switch (setjmp(uw_catch.ca.jb)) {   \
+    case 0:
+
 #define uw_catch_begin(MATCHES, SYMVAR, \
                        EXCVAR)          \
   obj_t *SYMVAR = nil;                  \
@@ -143,23 +150,21 @@ noreturn val type_mismatch(val, ...);
     switch (setjmp(uw_catch.ca.jb)) {   \
     case 0:
 
-#define uw_do_unwind                    \
-      goto uw_unwind_label
-
 #define uw_catch(SYMVAR, EXCVAR)        \
+    goto uw_unwind_label;               \
       break;                            \
     case 2:                             \
       EXCVAR = uw_catch.ca.exception;   \
       SYMVAR = uw_catch.ca.sym;
 
 #define uw_unwind                       \
-      break;                            \
     uw_unwind_label:                    \
     case 1:
 
 #define uw_catch_end                    \
-    default:                            \
       break;                            \
+    default:                            \
+      abort();                          \
     }                                   \
     if (uw_catch.ca.cont)               \
       uw_continue(&uw_catch,            \