From f57c1c8e2a3b4d084816e904005ffbd71e2dec86 Mon Sep 17 00:00:00 2001
From: Matthew Flatt <mflatt@racket-lang.org>
Date: Fri, 11 Jul 2014 13:23:30 +0100
Subject: [PATCH] fix GC-cooperation bug in `vector->values`

The `vector->values` function set up multiple return values
badly in the case that the given vector is chaperoned.
The problem could lead to NULL as results for `vector->values`.

Merge to v6.1
---
 .../racket-test/tests/racket/chaperone.rktl   |  8 +++++++
 racket/src/racket/src/vector.c                | 23 +++++++++++--------
 2 files changed, 21 insertions(+), 10 deletions(-)

diff --git a/pkgs/racket-pkgs/racket-test/tests/racket/chaperone.rktl b/pkgs/racket-pkgs/racket-test/tests/racket/chaperone.rktl
index 960941897b..385a2616bc 100644
--- a/pkgs/racket-pkgs/racket-test/tests/racket/chaperone.rktl
+++ b/pkgs/racket-pkgs/racket-test/tests/racket/chaperone.rktl
@@ -199,6 +199,14 @@
     (test #f vector-ref b 0)
     (test #f vector-ref b2 0)))
 
+;; check interaction of chaperones and vector->values:
+(let ([b (vector 1 2 3)])
+  (let ([b2 (impersonate-vector b
+                                (lambda (b i v) (collect-garbage) v)
+                                (lambda (b i v) #f))])
+    (define-values (a b c) (vector->values b2))
+    (test '(1 2 3) list a b c)))
+
 ;; ----------------------------------------
 
 (test #t chaperone?/impersonator (chaperone-procedure (lambda (x) x) (lambda (y) y)))
diff --git a/racket/src/racket/src/vector.c b/racket/src/racket/src/vector.c
index 981f572deb..7c7c771b90 100644
--- a/racket/src/racket/src/vector.c
+++ b/racket/src/racket/src/vector.c
@@ -771,7 +771,7 @@ static Scheme_Object *vector_to_immutable (int argc, Scheme_Object *argv[])
 static Scheme_Object *vector_to_values (int argc, Scheme_Object *argv[])
 {
   Scheme_Thread *p;
-  Scheme_Object *vec, **a;
+  Scheme_Object *vec, **a, *plain_vec;
   intptr_t len, start, finish, i;
 
   vec = argv[0];
@@ -807,6 +807,16 @@ static Scheme_Object *vector_to_values (int argc, Scheme_Object *argv[])
       return SCHEME_VEC_ELS(vec)[start];
   }
 
+  if (!SAME_OBJ(vec, argv[0])) {
+    plain_vec = scheme_make_vector(len, NULL);
+    for (i = 0; i < len; i++) {
+      vec = scheme_chaperone_vector_ref(argv[0], start + i);
+      SCHEME_VEC_ELS(plain_vec)[i] = vec;
+    }
+    vec = plain_vec;
+    start = 0;
+  }
+
   p = scheme_current_thread;
   if (p->values_buffer && (p->values_buffer_size >= len))
     a = p->values_buffer;
@@ -819,15 +829,8 @@ static Scheme_Object *vector_to_values (int argc, Scheme_Object *argv[])
   p->ku.multiple.array = a;
   p->ku.multiple.count = len;
 
-  if (!SAME_OBJ(vec, argv[0])) {
-    for (i = 0; i < len; i++) {
-      vec = scheme_chaperone_vector_ref(argv[0], start + i);
-      a[i] = vec;
-    }
-  } else {
-    for (i = 0; i < len; i++) {
-      a[i] = SCHEME_VEC_ELS(vec)[start + i];
-    }
+  for (i = 0; i < len; i++) {
+    a[i] = SCHEME_VEC_ELS(vec)[start + i];
   }
 
   return SCHEME_MULTIPLE_VALUES;