cmd/gc: string conversion for surrogates

This is required by the spec to produce the replacement char.
The fix lies in lib9's rune code.

R=golang-dev, nigeltao, rsc
CC=golang-dev
http://codereview.appspot.com/6443109

1 files changed, 23 insertions, 1 deletions

diff --git a/test/string_lit.go b/test/string_lit.go
index 956330038..457faaa88 100644
--- a/test/string_lit.go
+++ b/test/string_lit.go
@@ -93,7 +93,7 @@ func main() {
 		"backslashes 2 (backquote)")
 	assert("\\x\\u\\U\\", `\x\u\U\`, "backslash 3 (backquote)")
 
-	// test large runes. perhaps not the most logical place for this test.
+	// test large and surrogate-half runes. perhaps not the most logical place for these tests.
 	var r int32
 	r = 0x10ffff // largest rune value
 	s = string(r)
@@ -101,6 +101,28 @@ func main() {
 	r = 0x10ffff + 1
 	s = string(r)
 	assert(s, "\xef\xbf\xbd", "too-large rune")
+	r = 0xD800
+	s = string(r)
+	assert(s, "\xef\xbf\xbd", "surrogate rune min")
+	r = 0xDFFF
+	s = string(r)
+	assert(s, "\xef\xbf\xbd", "surrogate rune max")
+	r = -1
+	s = string(r)
+	assert(s, "\xef\xbf\xbd", "negative rune")
+	
+	// the large rune tests again, this time using constants instead of a variable.
+	// these conversions will be done at compile time.
+	s = string(0x10ffff) // largest rune value
+	assert(s, "\xf4\x8f\xbf\xbf", "largest rune constant")
+	s = string(0x10ffff + 1)
+	assert(s, "\xef\xbf\xbd", "too-large rune constant")
+	s = string(0xD800)
+	assert(s, "\xef\xbf\xbd", "surrogate rune min constant")
+	s = string(0xDFFF)
+	assert(s, "\xef\xbf\xbd", "surrogate rune max constant")
+	s = string(-1)
+	assert(s, "\xef\xbf\xbd", "negative rune")
 
 	assert(string(gr1), gx1, "global ->[]rune")
 	assert(string(gr2), gx2fix, "global invalid ->[]rune")