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reflect: make unsafe use of SliceHeader gc-friendly

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Revert workaround in compiler and
revert test for compiler workaround.

Tested that the 386 build continues to fail if
the gc change is made without the reflect change.

R=golang-dev, bradfitz
CC=golang-dev
https://golang.org/cl/5312041
This commit is contained in:
Russ Cox 2011-10-18 10:03:37 -04:00
parent 313c8224d5
commit 4e7aac5413
3 changed files with 21 additions and 81 deletions
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29
src/pkg/reflect/value.go
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@ -1424,11 +1424,17 @@ func (v Value) Slice(beg, end int) Value {
typ = iv.typ.toType()
base = (*SliceHeader)(iv.addr).Data
}
s := new(SliceHeader)
// Declare slice so that gc can see the base pointer in it.
var x []byte
// Reinterpret as *SliceHeader to edit.
s := (*SliceHeader)(unsafe.Pointer(&x))
s.Data = base + uintptr(beg)*typ.Elem().Size()
s.Len = end - beg
s.Cap = cap - beg
return valueFromAddr(iv.flag&flagRO, typ, unsafe.Pointer(s))
s.Cap = end - beg
return valueFromAddr(iv.flag&flagRO, typ, unsafe.Pointer(&x))
}
// String returns the string v's underlying value, as a string.
@ -1654,12 +1660,17 @@ func MakeSlice(typ Type, len, cap int) Value {
if typ.Kind() != Slice {
panic("reflect: MakeSlice of non-slice type")
}
s := &SliceHeader{
Data: uintptr(unsafe.NewArray(typ.Elem(), cap)),
Len: len,
Cap: cap,
}
return valueFromAddr(0, typ, unsafe.Pointer(s))
// Declare slice so that gc can see the base pointer in it.
var x []byte
// Reinterpret as *SliceHeader to edit.
s := (*SliceHeader)(unsafe.Pointer(&x))
s.Data = uintptr(unsafe.NewArray(typ.Elem(), cap))
s.Len = len
s.Cap = cap
return valueFromAddr(0, typ, unsafe.Pointer(&x))
}
// MakeChan creates a new channel with the specified type and buffer size.