test: test handling of negative float constants

This used to panic when compiled by gccgo.

Updates #2876.

R=golang-dev, rsc
CC=golang-dev
https://golang.org/cl/6100055

diff --git a/test/fixedbugs/bug434.go b/test/fixedbugs/bug434.go
new file mode 100644 (file)
index 0000000..5abb567
--- /dev/null
+++ b/test/fixedbugs/bug434.go
@@ -0,0 +1,32 @@
+// run
+
+// Copyright 2012 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+// Test that typed and untyped negative zero floating point constants
+// are treated as equivalent to zero constants.
+
+package main
+
+import "math"
+
+const zero = 0.0
+
+func main() {
+       x := -zero
+       b := math.Float64bits(x)
+       if b != 0 {
+               panic(b)
+       }
+       x = -float64(zero)
+       b = math.Float64bits(x)
+       if b != 0 {
+               panic(b)
+       }
+       v := x
+       b = math.Float64bits(-v)
+       if b != 0x8000000000000000 {
+               panic(b)
+       }
+}