Context form error reporting in sys:capture-cont.

* unwind.c (sys_capture_cont_s): New variable.
(uw_capture_cont): Second argument is now a context
form rather than a symbol; eval_error is used for error
reporting. The form's operator symbol si used in the
error message, or else sys:capture-cont if the
context argument is null or missing.
(uw_late_init): Initialize sys_capture_cont_s.

* unwind.h (uw_capture_cont): Declaration updated.

* txr.1: Documented.

1 files changed, 9 insertions, 6 deletions

diff --git a/unwind.c b/unwind.c
index 0202f4e4..fe3c68b6 100644
--- a/unwind.c
+++ b/unwind.c
@@ -51,6 +51,7 @@ static uw_frame_t *uw_exit_point;
 static uw_frame_t toplevel_env;
 
 static val unhandled_hook_s, types_s, jump_s, sys_cont_s;
+static val sys_capture_cont_s;
 
 static val frame_type, catch_frame_type, handle_frame_type;
 
@@ -746,7 +747,7 @@ static val capture_cont(val tag, uw_frame_t *block)
   return result;
 }
 
-val uw_capture_cont(val tag, val ctx)
+val uw_capture_cont(val tag, val ctx_form)
 {
   uw_frame_t *fr;
 
@@ -757,12 +758,13 @@ val uw_capture_cont(val tag, val ctx)
   }
 
   if (!fr) {
+    uses_or2;
+    val sym = or2(car(default_bool_arg(ctx_form)), sys_capture_cont_s);
+
     if (tag)
-      uw_throwf(error_s, lit("~s: no block ~s is visible"),
-                ctx, tag, nao);
+      eval_error(ctx_form, lit("~s: no block ~s is visible"), sym, tag, nao);
     else
-      uw_throwf(error_s, lit("~s: no anonymous block is visible"),
-                ctx, nao);
+      eval_error(ctx_form, lit("~s: no anonymous block is visible"), sym, nao);
     abort();
   }
 
@@ -812,5 +814,6 @@ void uw_late_init(void)
   reg_fun(intern(lit("find-frame"), user_package), func_n2o(uw_find_frame, 0));
   reg_fun(intern(lit("invoke-catch"), user_package),
           func_n2v(uw_invoke_catch));
-  reg_fun(intern(lit("capture-cont"), system_package), func_n2(uw_capture_cont));
+  reg_fun(sys_capture_cont_s = intern(lit("capture-cont"), system_package),
+          func_n2o(uw_capture_cont, 1));
 }