go/pointer: fix panic due to bogus constraint from value,ok receive operation.
See regression test for explanation.
I audited the code for similar issues and found none.
Many thanks to Daniel Morsing for providing a small
reproducible test case, a rarity for PTA bugs!
Fixes golang/go#9002
LGTM=crawshaw
R=crawshaw
CC=daniel.morsing, golang-codereviews
https://golang.org/cl/163350043
diff --git a/go/pointer/gen.go b/go/pointer/gen.go
index d8f96a7..cfd8241 100644
--- a/go/pointer/gen.go
+++ b/go/pointer/gen.go
@@ -936,7 +936,8 @@
case token.ARROW: // <-x
// We can ignore instr.CommaOk because the node we're
// altering is always at zero offset relative to instr
- a.genLoad(cgn, a.valueNode(instr), instr.X, 0, a.sizeof(instr.Type()))
+ tElem := instr.X.Type().Underlying().(*types.Chan).Elem()
+ a.genLoad(cgn, a.valueNode(instr), instr.X, 0, a.sizeof(tElem))
case token.MUL: // *x
a.genLoad(cgn, a.valueNode(instr), instr.X, 0, a.sizeof(instr.Type()))
diff --git a/go/pointer/pointer_test.go b/go/pointer/pointer_test.go
index ae521d1..7c10693 100644
--- a/go/pointer/pointer_test.go
+++ b/go/pointer/pointer_test.go
@@ -46,6 +46,7 @@
"testdata/funcreflect.go",
"testdata/hello.go", // NB: causes spurious failure of HVN cross-check
"testdata/interfaces.go",
+ "testdata/issue9002.go",
"testdata/mapreflect.go",
"testdata/maps.go",
"testdata/panic.go",
diff --git a/go/pointer/testdata/issue9002.go b/go/pointer/testdata/issue9002.go
new file mode 100644
index 0000000..b7c2c61
--- /dev/null
+++ b/go/pointer/testdata/issue9002.go
@@ -0,0 +1,17 @@
+package main
+
+func main() {
+ // Regression test for golang issue 9002.
+ //
+ // The two-result "value,ok" receive operation generated a
+ // too-wide constraint loading (value int, ok bool), not bool,
+ // from the channel.
+ //
+ // This bug manifested itself in an out-of-bounds array access
+ // when the makechan object was the highest-numbered node, as in
+ // this program.
+ //
+ // In more realistic programs it silently resulted in bogus
+ // constraints.
+ _, _ = <-make(chan int)
+}
