array index bug

x[i]
x not addressable, i >= UINF
double evaluated i
second eval killed live registers

manifested as gob instability

R=ken
OCL=34097
CL=34099

diff --git a/src/cmd/6g/cgen.c b/src/cmd/6g/cgen.c
index ab712e5435e93abff78ccf2913c0cec2d1b6e2a6..2f2b2d9eb24c0f05a52c57a9b06a4a72eaae1bc5 100644 (file)
--- a/src/cmd/6g/cgen.c
+++ b/src/cmd/6g/cgen.c
@@ -470,9 +470,9 @@ agen(Node *n, Node *res)
                        agen(nl, &n3);
                        goto index;
                }
-               cgen(nr, res);
                tempname(&tmp, nr->type);
-               gmove(res, &tmp);
+               cgen(nr, &tmp);
+               nr = &tmp;
 
        irad:
                regalloc(&n3, types[tptr], res);
@@ -792,7 +792,7 @@ bgen(Node *n, int true, Prog *to)
                        regfree(&n1);
                        break;
                }
-               
+
                if(isinter(nl->type)) {
                        // front end shold only leave cmp to literal nil
                        if((a != OEQ && a != ONE) || nr->op != OLITERAL) {

diff --git a/test/fixedbugs/bug199.go b/test/fixedbugs/bug199.go
new file mode 100644 (file)
index 0000000..c7bd21f
--- /dev/null
+++ b/test/fixedbugs/bug199.go
@@ -0,0 +1,25 @@
+// $G $D/$F.go && $L $F.$A && ./$A.out
+
+// Copyright 2009 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package main
+
+type S struct {
+       a []int;
+}
+var s = &S{make([]int, 10)}
+
+func main() {
+       s.a[f()] = 1    // 6g used to call f twice here
+}
+
+var n int
+func f() int{
+       if n++; n > 1 {
+               panicln("f twice");
+       }
+       return 0
+}
+