cmd/compile: fix mishandling of unsafe-uintptr arguments in go/defer

Currently, the statement:

	go g(uintptr(f()))

gets rewritten into:

	tmp := f()
	newproc(8, g, uintptr(tmp))
	runtime.KeepAlive(tmp)

which doesn't guarantee that tmp is still alive by time the g call is
scheduled to run.

This CL fixes the issue, by wrapping g call in a closure:

	go func(p unsafe.Pointer) {
		g(uintptr(p))
	}(f())

then this will be rewritten into:

	tmp := f()
	go func(p unsafe.Pointer) {
		g(uintptr(p))
		runtime.KeepAlive(p)
	}(tmp)
	runtime.KeepAlive(tmp)  // superfluous, but harmless

So the unsafe.Pointer p will be kept alive at the time g call runs.

Updates #24491

Change-Id: Ic10821251cbb1b0073daec92b82a866c6ebaf567
Reviewed-on: https://go-review.googlesource.com/c/go/+/253457
Run-TryBot: Cuong Manh Le <cuong.manhle.vn@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>

1 files changed, 28 insertions, 13 deletions

diff --git a/src/cmd/compile/internal/gc/syntax.go b/src/cmd/compile/internal/gc/syntax.go
index 47e5e59156..5580f789c5 100644
--- a/src/cmd/compile/internal/gc/syntax.go
+++ b/src/cmd/compile/internal/gc/syntax.go
@@ -141,19 +141,20 @@ const (
 	nodeInitorder, _                   // tracks state during init1; two bits
 	_, _                               // second nodeInitorder bit
 	_, nodeHasBreak
-	_, nodeNoInline  // used internally by inliner to indicate that a function call should not be inlined; set for OCALLFUNC and OCALLMETH only
-	_, nodeImplicit  // implicit OADDR or ODEREF; ++/-- statement represented as OASOP; or ANDNOT lowered to OAND
-	_, nodeIsDDD     // is the argument variadic
-	_, nodeDiag      // already printed error about this
-	_, nodeColas     // OAS resulting from :=
-	_, nodeNonNil    // guaranteed to be non-nil
-	_, nodeTransient // storage can be reused immediately after this statement
-	_, nodeBounded   // bounds check unnecessary
-	_, nodeHasCall   // expression contains a function call
-	_, nodeLikely    // if statement condition likely
-	_, nodeHasVal    // node.E contains a Val
-	_, nodeHasOpt    // node.E contains an Opt
-	_, nodeEmbedded  // ODCLFIELD embedded type
+	_, nodeNoInline     // used internally by inliner to indicate that a function call should not be inlined; set for OCALLFUNC and OCALLMETH only
+	_, nodeImplicit     // implicit OADDR or ODEREF; ++/-- statement represented as OASOP; or ANDNOT lowered to OAND
+	_, nodeIsDDD        // is the argument variadic
+	_, nodeDiag         // already printed error about this
+	_, nodeColas        // OAS resulting from :=
+	_, nodeNonNil       // guaranteed to be non-nil
+	_, nodeTransient    // storage can be reused immediately after this statement
+	_, nodeBounded      // bounds check unnecessary
+	_, nodeHasCall      // expression contains a function call
+	_, nodeLikely       // if statement condition likely
+	_, nodeHasVal       // node.E contains a Val
+	_, nodeHasOpt       // node.E contains an Opt
+	_, nodeEmbedded     // ODCLFIELD embedded type
+	_, nodeNeedsWrapper // OCALLxxx node that needs to be wrapped
 )
 
 func (n *Node) Class() Class     { return Class(n.flags.get3(nodeClass)) }
@@ -286,6 +287,20 @@ func (n *Node) SetIota(x int64) {
 	n.Xoffset = x
 }
 
+func (n *Node) NeedsWrapper() bool {
+	return n.flags&nodeNeedsWrapper != 0
+}
+
+// SetNeedsWrapper indicates that OCALLxxx node needs to be wrapped by a closure.
+func (n *Node) SetNeedsWrapper(b bool) {
+	switch n.Op {
+	case OCALLFUNC, OCALLMETH, OCALLINTER:
+	default:
+		Fatalf("Node.SetNeedsWrapper %v", n.Op)
+	}
+	n.flags.set(nodeNeedsWrapper, b)
+}
+
 // mayBeShared reports whether n may occur in multiple places in the AST.
 // Extra care must be taken when mutating such a node.
 func (n *Node) mayBeShared() bool {