cmd/compile: allow conversion from slice to array ptr

Panic if the slice is too short.

Updates #395

Change-Id: I90f4bff2da5d8f3148ba06d2482084f32b25c29a
Reviewed-on: https://go-review.googlesource.com/c/go/+/301650
Trust: Josh Bleecher Snyder <josharian@gmail.com>
Run-TryBot: Josh Bleecher Snyder <josharian@gmail.com>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>

1 files changed, 7 insertions, 0 deletions

diff --git a/src/runtime/panic.go b/src/runtime/panic.go
index f8f2f39dbb..f6c38aafcc 100644
--- a/src/runtime/panic.go
+++ b/src/runtime/panic.go
@@ -160,6 +160,12 @@ func goPanicSlice3CU(x uint, y int) {
 	panic(boundsError{x: int64(x), signed: false, y: y, code: boundsSlice3C})
 }
 
+// failures in the conversion (*[x]T)s, 0 <= x <= y, x == cap(s)
+func goPanicSliceConvert(x int, y int) {
+	panicCheck1(getcallerpc(), "slice length too short to convert to pointer to array")
+	panic(boundsError{x: int64(x), signed: true, y: y, code: boundsConvert})
+}
+
 // Implemented in assembly, as they take arguments in registers.
 // Declared here to mark them as ABIInternal.
 func panicIndex(x int, y int)
@@ -178,6 +184,7 @@ func panicSlice3B(x int, y int)
 func panicSlice3BU(x uint, y int)
 func panicSlice3C(x int, y int)
 func panicSlice3CU(x uint, y int)
+func panicSliceConvert(x int, y int)
 
 var shiftError = error(errorString("negative shift amount"))