internal/syscall/windows/registry: make '-gcflags=all=-d=checkptr' flag work

Mostly replaced [:x] slice operation with [:x:x]. 

According to @mdempsky, compiler specially recognizes when you combine
a pointer conversion with a full slice operation in a single expression
and makes an exception.

Updates golang/go#34972

Change-Id: I07d9de3b31da254d55f50d14c18155f8fc8f3ece
Reviewed-on: https://go-review.googlesource.com/c/go/+/203442
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Reviewed-by: Jason A. Donenfeld <Jason@zx2c4.com>

diff --git a/src/internal/syscall/windows/registry/value.go b/src/internal/syscall/windows/registry/value.go
index f8431d2c0f2b696662c8799cf697983f15cbb72a..bf8ab007590941e7a75b65ee7f63adc2dd7f37f6 100644 (file)
--- a/src/internal/syscall/windows/registry/value.go
+++ b/src/internal/syscall/windows/registry/value.go
@@ -108,7 +108,7 @@ func (k Key) GetStringValue(name string) (val string, valtype uint32, err error)
        if len(data) == 0 {
                return "", typ, nil
        }
-       u := (*[1 << 29]uint16)(unsafe.Pointer(&data[0]))[:len(data)/2]
+       u := (*[1 << 29]uint16)(unsafe.Pointer(&data[0]))[: len(data)/2 : len(data)/2]
        return syscall.UTF16ToString(u), typ, nil
 }
 
@@ -185,8 +185,7 @@ func ExpandString(value string) (string, error) {
                        return "", err
                }
                if n <= uint32(len(r)) {
-                       u := (*[1 << 29]uint16)(unsafe.Pointer(&r[0]))[:]
-                       return syscall.UTF16ToString(u), nil
+                       return syscall.UTF16ToString(r[:n]), nil
                }
                r = make([]uint16, n)
        }
@@ -208,7 +207,7 @@ func (k Key) GetStringsValue(name string) (val []string, valtype uint32, err err
        if len(data) == 0 {
                return nil, typ, nil
        }
-       p := (*[1 << 29]uint16)(unsafe.Pointer(&data[0]))[:len(data)/2]
+       p := (*[1 << 29]uint16)(unsafe.Pointer(&data[0]))[: len(data)/2 : len(data)/2]
        if len(p) == 0 {
                return nil, typ, nil
        }
@@ -296,7 +295,7 @@ func (k Key) setStringValue(name string, valtype uint32, value string) error {
        if err != nil {
                return err
        }
-       buf := (*[1 << 29]byte)(unsafe.Pointer(&v[0]))[:len(v)*2]
+       buf := (*[1 << 29]byte)(unsafe.Pointer(&v[0]))[: len(v)*2 : len(v)*2]
        return k.setValue(name, valtype, buf)
 }
 
@@ -326,7 +325,7 @@ func (k Key) SetStringsValue(name string, value []string) error {
                ss += s + "\x00"
        }
        v := utf16.Encode([]rune(ss + "\x00"))
-       buf := (*[1 << 29]byte)(unsafe.Pointer(&v[0]))[:len(v)*2]
+       buf := (*[1 << 29]byte)(unsafe.Pointer(&v[0]))[: len(v)*2 : len(v)*2]
        return k.setValue(name, MULTI_SZ, buf)
 }