ruby-core


>>>>> "matz" == Yukihiro Matsumoto <matz@ruby-lang.org> writes:

    matz> Hi, Good question.  But it needs a few spare days to
    matz> inspect.  Sorry for my weak memory.

    ctm> I wrote some code that creates a continuation in a process,
    ctm> forks and trys to call the continuation.  It fails with a
    ctm> "continuation called across trap" Runtime error, due to--I
    ctm> believe--a combination of rb_protect in rb_f_fork (process.c)
    ctm> and the test at the beginning of rb_cont_call (eval.c).

Cool.  It's definitely super low-priority.

Before you replied, I had already written and tested the attached
patch.  I've also attached a test program.  Without the patch it will
fail, with the patch it (and my more practical program) will run.

-- 
Cliff Matthews <ctm@ardi.com>

Attachments (2)

fork_cont.patch (2.31 KB, text/x-diff)

diff -ruN ruby-1.8.5.orig/eval.c ruby-1.8.5/eval.c
--- ruby-1.8.5.orig/eval.c	2006-08-06 21:43:39.000000000 -0600
+++ ruby-1.8.5/eval.c	2006-10-02 12:24:57.000000000 -0600
@@ -5410,21 +5410,24 @@
 
 static VALUE cont_protect;
 
-VALUE
-rb_protect(proc, data, state)
+static VALUE
+rb_protect_helper(proc, data, state, need_new_cont_protect)
     VALUE (*proc) _((VALUE));
     VALUE data;
     int *state;
+    int need_new_cont_protect;
 {
     VALUE result = Qnil;	/* OK */
     int status;
 
     PUSH_TAG(PROT_NONE);
-    cont_protect = (VALUE)rb_node_newnode(NODE_MEMO, cont_protect, 0, 0);
+    if (need_new_cont_protect)
+	cont_protect = (VALUE)rb_node_newnode(NODE_MEMO, cont_protect, 0, 0);
     if ((status = EXEC_TAG()) == 0) {
 	result = (*proc)(data);
     }
-    cont_protect = ((NODE *)cont_protect)->u1.value;
+    if (need_new_cont_protect)
+        cont_protect = ((NODE *)cont_protect)->u1.value;
     POP_TAG();
     if (state) {
 	*state = status;
@@ -5437,6 +5440,25 @@
 }
 
 VALUE
+rb_protect(proc, data, state)
+    VALUE (*proc) _((VALUE));
+    VALUE data;
+    int *state;
+{
+  return rb_protect_helper(proc, data, state, Qtrue);
+}
+
+VALUE
+rb_protect_fork(proc, data, state)
+    VALUE (*proc) _((VALUE));
+    VALUE data;
+    int *state;
+{
+  return rb_protect_helper(proc, data, state, Qfalse);
+}
+
+
+VALUE
 rb_ensure(b_proc, data1, e_proc, data2)
     VALUE (*b_proc)();
     VALUE data1;
diff -ruN ruby-1.8.5.orig/intern.h ruby-1.8.5/intern.h
--- ruby-1.8.5.orig/intern.h	2006-05-15 18:25:18.000000000 -0600
+++ ruby-1.8.5/intern.h	2006-10-02 12:25:22.000000000 -0600
@@ -185,6 +185,7 @@
 VALUE rb_f_lambda _((void));
 VALUE rb_proc_new _((VALUE (*)(ANYARGS/* VALUE yieldarg[, VALUE procarg] */), VALUE));
 VALUE rb_protect _((VALUE (*)(VALUE), VALUE, int*));
+VALUE rb_protect_fork _((VALUE (*)(VALUE), VALUE, int*));
 void rb_set_end_proc _((void (*)(VALUE), VALUE));
 void rb_mark_end_proc _((void));
 void rb_exec_end_proc _((void));
diff -ruN ruby-1.8.5.orig/process.c ruby-1.8.5/process.c
--- ruby-1.8.5.orig/process.c	2006-08-15 20:46:10.000000000 -0600
+++ ruby-1.8.5/process.c	2006-10-02 12:25:33.000000000 -0600
@@ -1284,7 +1284,7 @@
 	if (rb_block_given_p()) {
 	    int status;
 
-	    rb_protect(rb_yield, Qundef, &status);
+	    rb_protect_fork(rb_yield, Qundef, &status);
 	    ruby_stop(status);
 	}
 	return Qnil;

fork_cont_test.rb (271 Bytes, application/x-sh)

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