// genConv generates constraints for the conversion operation conv.
func (a *analysis) genConv(conv *ssa.Convert, cgn *cgnode) {
res := a.valueNode(conv)
if res == 0 {
return // result is non-pointerlike
}
tSrc := conv.X.Type()
tDst := conv.Type()
switch utSrc := tSrc.Underlying().(type) {
case *types.Slice:
// []byte/[]rune -> string?
return
case *types.Pointer:
// *T -> unsafe.Pointer?
if tDst.Underlying() == tUnsafePtr {
return // we don't model unsafe aliasing (unsound)
}
case *types.Basic:
switch tDst.Underlying().(type) {
case *types.Pointer:
// Treat unsafe.Pointer->*T conversions like
// new(T) and create an unaliased object.
if utSrc == tUnsafePtr {
obj := a.addNodes(mustDeref(tDst), "unsafe.Pointer conversion")
a.endObject(obj, cgn, conv)
a.addressOf(tDst, res, obj)
return
}
case *types.Slice:
// string -> []byte/[]rune (or named aliases)?
if utSrc.Info()&types.IsString != 0 {
obj := a.addNodes(sliceToArray(tDst), "convert")
a.endObject(obj, cgn, conv)
a.addressOf(tDst, res, obj)
return
}
case *types.Basic:
// All basic-to-basic type conversions are no-ops.
// This includes uintptr<->unsafe.Pointer conversions,
// which we (unsoundly) ignore.
return
}
}
panic(fmt.Sprintf("illegal *ssa.Convert %s -> %s: %s", tSrc, tDst, conv.Parent()))
}
// genConv generates constraints for the conversion operation conv.
func (a *analysis) genConv(conv *ssa.Convert, cgn *cgnode) {
res := a.valueNode(conv)
if res == 0 {
return // result is non-pointerlike
}
tSrc := conv.X.Type()
tDst := conv.Type()
switch utSrc := tSrc.Underlying().(type) {
case *types.Slice:
// []byte/[]rune -> string?
return
case *types.Pointer:
// *T -> unsafe.Pointer?
if tDst.Underlying() == tUnsafePtr {
// ignore for now
// a.copy(res, a.valueNode(conv.X), 1)
return
}
case *types.Basic:
switch utDst := tDst.Underlying().(type) {
case *types.Pointer:
// unsafe.Pointer -> *T? (currently unsound)
if utSrc == tUnsafePtr {
// For now, suppress unsafe.Pointer conversion
// warnings on "syscall" package.
// TODO(adonovan): audit for soundness.
if conv.Parent().Pkg.Object.Path() != "syscall" {
a.warnf(conv.Pos(),
"unsound: %s contains an unsafe.Pointer conversion (to %s)",
conv.Parent(), tDst)
}
// For now, we treat unsafe.Pointer->*T
// conversion like new(T) and create an
// unaliased object. In future we may handle
// unsafe conversions soundly; see TODO file.
obj := a.addNodes(mustDeref(tDst), "unsafe.Pointer conversion")
a.endObject(obj, cgn, conv)
a.addressOf(tDst, res, obj)
return
}
case *types.Slice:
// string -> []byte/[]rune (or named aliases)?
if utSrc.Info()&types.IsString != 0 {
obj := a.addNodes(sliceToArray(tDst), "convert")
a.endObject(obj, cgn, conv)
a.addressOf(tDst, res, obj)
return
}
case *types.Basic:
// TODO(adonovan):
// unsafe.Pointer -> uintptr?
// uintptr -> unsafe.Pointer
//
// The language doesn't adequately specify the
// behaviour of these operations, but almost
// all uses of these conversions (even in the
// spec) seem to imply a non-moving garbage
// collection strategy, or implicit "pinning"
// semantics for unsafe.Pointer conversions.
// TODO(adonovan): we need more work before we can handle
// cryptopointers well.
if utSrc == tUnsafePtr || utDst == tUnsafePtr {
// Ignore for now. See TODO file for ideas.
return
}
return // ignore all other basic type conversions
}
}
panic(fmt.Sprintf("illegal *ssa.Convert %s -> %s: %s", tSrc, tDst, conv.Parent()))
}