[release-branch.go1.4] reflect: add kindNoPointers if a function layout has no pointers.

malloc checks kindNoPointers and if it is not set and the object
is one pointer in size, it assumes it contains a pointer.  So we
must set kindNoPointers correctly; it isn't just a hint.

Fixes #9425

Change-Id: Ia43da23cc3298d6e3d6dbdf66d32e9678f0aedcf
Reviewed-on: https://go-review.googlesource.com/2055
Reviewed-by: Russ Cox <rsc@golang.org>
(cherry picked from commit d11f41118116e0b5c2fb3b3296323d888dff2d6e)
Reviewed-on: https://go-review.googlesource.com/2800
Reviewed-by: Andrew Gerrand <adg@golang.org>

diff --git a/src/reflect/type.go b/src/reflect/type.go
index c0ddfcad0ad1f31266435564387147376187e338..99712495b605e3fbff5e1b01a1ce1b9332824757 100644 (file)
--- a/src/reflect/type.go
+++ b/src/reflect/type.go
@@ -1498,8 +1498,9 @@ func MapOf(key, elem Type) Type {
 
 // gcProg is a helper type for generatation of GC pointer info.
 type gcProg struct {
-       gc   []byte
-       size uintptr // size of type in bytes
+       gc     []byte
+       size   uintptr // size of type in bytes
+       hasPtr bool
 }
 
 func (gc *gcProg) append(v byte) {
@@ -1560,11 +1561,14 @@ func (gc *gcProg) appendWord(v byte) {
        gc.gc[nptr/2] &= ^(3 << ((nptr%2)*4 + 2))
        gc.gc[nptr/2] |= v << ((nptr%2)*4 + 2)
        gc.size += ptrsize
+       if v == bitsPointer {
+               gc.hasPtr = true
+       }
 }
 
-func (gc *gcProg) finalize() unsafe.Pointer {
+func (gc *gcProg) finalize() (unsafe.Pointer, bool) {
        if gc.size == 0 {
-               return nil
+               return nil, false
        }
        ptrsize := unsafe.Sizeof(uintptr(0))
        gc.align(ptrsize)
@@ -1579,7 +1583,7 @@ func (gc *gcProg) finalize() unsafe.Pointer {
                        gc.appendWord(extractGCWord(gc.gc, i))
                }
        }
-       return unsafe.Pointer(&gc.gc[0])
+       return unsafe.Pointer(&gc.gc[0]), gc.hasPtr
 }
 
 func extractGCWord(gc []byte, i uintptr) byte {
@@ -1639,7 +1643,7 @@ func bucketOf(ktyp, etyp *rtype) *rtype {
 
        b := new(rtype)
        b.size = gc.size
-       b.gc[0] = gc.finalize()
+       b.gc[0], _ = gc.finalize()
        s := "bucket(" + *ktyp.string + "," + *etyp.string + ")"
        b.string = &s
        return b
@@ -1840,7 +1844,11 @@ func funcLayout(t *rtype, rcvr *rtype) (frametype *rtype, argSize, retOffset uin
        // build dummy rtype holding gc program
        x := new(rtype)
        x.size = gc.size
-       x.gc[0] = gc.finalize()
+       var hasPtr bool
+       x.gc[0], hasPtr = gc.finalize()
+       if !hasPtr {
+               x.kind |= kindNoPointers
+       }
        var s string
        if rcvr != nil {
                s = "methodargs(" + *rcvr.string + ")(" + *t.string + ")"