Add support for limited mode without unsafe pkg.

This commit adds support for compiling spew without the unsafe package.
When compiled without the unsafe package, some of the more advanced
features such as invoking stringers on pointers from non-pointer
variables and unexported struct fields are not available.

By default, spew will be compiled in the limited mode for Google App
Engine since the unsafe package is not available there.  Additionally,
spew can be compiled without the unsafe package manually by specifying
the "disableunsafe" build tag.

Finally, a new package-level constant named "UnsafeDisabled" has been
exposed which can be used to programmatically determine if spew was
compiled with access to the unsafe package.

1 files changed, 101 insertions, 0 deletions

diff --git a/spew/internalunsafe_test.go b/spew/internalunsafe_test.go
new file mode 100644
index 0000000..83e070e
--- /dev/null
+++ b/spew/internalunsafe_test.go
@@ -0,0 +1,101 @@
+// Copyright (c) 2013-2015 Dave Collins <[email protected]>
+
+// Permission to use, copy, modify, and distribute this software for any
+// purpose with or without fee is hereby granted, provided that the above
+// copyright notice and this permission notice appear in all copies.
+
+// THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+// WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+// MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+// ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+// WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+// ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+// OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+
+// NOTE: Due to the following build constraints, this file will only be compiled
+// when the code is not running on Google App Engine and "-tags disableunsafe"
+// is not added to the go build command line.
+// +build !appengine,!disableunsafe
+
+/*
+This test file is part of the spew package rather than than the spew_test
+package because it needs access to internals to properly test certain cases
+which are not possible via the public interface since they should never happen.
+*/
+
+package spew
+
+import (
+	"bytes"
+	"reflect"
+	"testing"
+	"unsafe"
+)
+
+// changeKind uses unsafe to intentionally change the kind of a reflect.Value to
+// the maximum kind value which does not exist.  This is needed to test the
+// fallback code which punts to the standard fmt library for new types that
+// might get added to the language.
+func changeKind(v *reflect.Value, readOnly bool) {
+	rvf := (*uintptr)(unsafe.Pointer(uintptr(unsafe.Pointer(v)) + offsetFlag))
+	*rvf = *rvf | ((1<<flagKindWidth - 1) << flagKindShift)
+	if readOnly {
+		*rvf |= flagRO
+	} else {
+		*rvf &= ^uintptr(flagRO)
+	}
+}
+
+// TestAddedReflectValue tests functionaly of the dump and formatter code which
+// falls back to the standard fmt library for new types that might get added to
+// the language.
+func TestAddedReflectValue(t *testing.T) {
+	i := 1
+
+	// Dump using a reflect.Value that is exported.
+	v := reflect.ValueOf(int8(5))
+	changeKind(&v, false)
+	buf := new(bytes.Buffer)
+	d := dumpState{w: buf, cs: &Config}
+	d.dump(v)
+	s := buf.String()
+	want := "(int8) 5"
+	if s != want {
+		t.Errorf("TestAddedReflectValue #%d\n got: %s want: %s", i, s, want)
+	}
+	i++
+
+	// Dump using a reflect.Value that is not exported.
+	changeKind(&v, true)
+	buf.Reset()
+	d.dump(v)
+	s = buf.String()
+	want = "(int8) <int8 Value>"
+	if s != want {
+		t.Errorf("TestAddedReflectValue #%d\n got: %s want: %s", i, s, want)
+	}
+	i++
+
+	// Formatter using a reflect.Value that is exported.
+	changeKind(&v, false)
+	buf2 := new(dummyFmtState)
+	f := formatState{value: v, cs: &Config, fs: buf2}
+	f.format(v)
+	s = buf2.String()
+	want = "5"
+	if s != want {
+		t.Errorf("TestAddedReflectValue #%d got: %s want: %s", i, s, want)
+	}
+	i++
+
+	// Formatter using a reflect.Value that is not exported.
+	changeKind(&v, true)
+	buf2.Reset()
+	f = formatState{value: v, cs: &Config, fs: buf2}
+	f.format(v)
+	s = buf2.String()
+	want = "<int8 Value>"
+	if s != want {
+		t.Errorf("TestAddedReflectValue #%d got: %s want: %s", i, s, want)
+	}
+}