cmd/internal/gc: move check for large-hence-heap-allocated types into escape analysis
Before this change, the check for too-large arrays (and other large
types) occurred after escape analysis. If the data moved off stack
and onto the heap contained any pointers, it would therefore escape,
but because the too-large check occurred after escape analysis this
would not be recorded and a stack pointer would leak to the heap
(see the modified escape_array.go for an example).
Some of these appear to remain, in calls to typecheck from within walk.
Also corrected a few comments in escape_array.go about "BAD"
analysis that is now done correctly.
Enhanced to move aditional EscNone-but-large-so-heap checks into esc.c.
Change-Id: I770c111baff28a9ed5f8beb601cf09dacc561b83
Reviewed-on: https://go-review.googlesource.com/10268
Reviewed-by: Russ Cox <rsc@golang.org>
diff --git a/src/cmd/compile/internal/gc/walk.go b/src/cmd/compile/internal/gc/walk.go
index b5b8611..1111766 100644
--- a/src/cmd/compile/internal/gc/walk.go
+++ b/src/cmd/compile/internal/gc/walk.go
@@ -352,6 +352,20 @@
*np = n
}
+func isSmallMakeSlice(n *Node) bool {
+ if n.Op != OMAKESLICE {
+ return false
+ }
+ l := n.Left
+ r := n.Right
+ if r == nil {
+ r = l
+ }
+ t := n.Type
+
+ return Smallintconst(l) && Smallintconst(r) && (t.Type.Width == 0 || Mpgetfix(r.Val.U.(*Mpint)) < (1<<16)/t.Type.Width)
+}
+
/*
* walk the whole tree of the body of an
* expression or simple statement.
@@ -1320,7 +1334,10 @@
goto ret
case ONEW:
- if n.Esc == EscNone && n.Type.Type.Width < 1<<16 {
+ if n.Esc == EscNone {
+ if n.Type.Type.Width >= 1<<16 {
+ Fatal("Large ONEW with EscNone, %v", n)
+ }
r := temp(n.Type.Type)
r = Nod(OAS, r, nil) // zero temp
typecheck(&r, Etop)
@@ -1458,7 +1475,10 @@
l = r
}
t := n.Type
- if n.Esc == EscNone && Smallintconst(l) && Smallintconst(r) && (t.Type.Width == 0 || Mpgetfix(r.Val.U.(*Mpint)) < (1<<16)/t.Type.Width) {
+ if n.Esc == EscNone {
+ if !isSmallMakeSlice(n) {
+ Fatal("Non-small OMAKESLICE with EscNone, %v", n)
+ }
// var arr [r]T
// n = arr[:l]
t = aindex(r, t.Type) // [r]T
