strconv: check for empty string in UnquoteChar

The existing implementation panics on malformed input of an empty
string. strconv.Unquote validates the length of the inputs, but calling
UnquoteChar directly with an empty string leads to a panic, so add a
check for length. Also, add a test to go/constant to ensure that
MakeFromLiteral does not panic on malformed input such as
"const x = ''".

Change-Id: I4217e38db48a09a21ec414bbfb3087709da62904
Reviewed-on: https://go-review.googlesource.com/116215
Run-TryBot: Robert Griesemer <gri@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Robert Griesemer <gri@golang.org>

diff --git a/src/go/constant/value_test.go b/src/go/constant/value_test.go
index 5ec4f4c41853499140c6e559beb17b2443222bb2..e6fca76e182bc8f15b866015c0e54c963329b35c 100644 (file)
--- a/src/go/constant/value_test.go
+++ b/src/go/constant/value_test.go
@@ -431,6 +431,7 @@ func TestUnknown(t *testing.T) {
                MakeBool(false), // token.ADD ok below, operation is never considered
                MakeString(""),
                MakeInt64(1),
+               MakeFromLiteral("''", token.CHAR, 0),
                MakeFromLiteral("-1234567890123456789012345678901234567890", token.INT, 0),
                MakeFloat64(1.2),
                MakeImag(MakeFloat64(1.2)),

diff --git a/src/strconv/quote.go b/src/strconv/quote.go
index d514b5f552795e3d0d66fa8574ab59054b023ddb..9b7194a0f041d456de6d51c6b16174f9b6062df8 100644 (file)
--- a/src/strconv/quote.go
+++ b/src/strconv/quote.go
@@ -237,6 +237,10 @@ func unhex(b byte) (v rune, ok bool) {
 // If set to zero, it does not permit either escape and allows both quote characters to appear unescaped.
 func UnquoteChar(s string, quote byte) (value rune, multibyte bool, tail string, err error) {
        // easy cases
+       if len(s) == 0 {
+               err = ErrSyntax
+               return
+       }
        switch c := s[0]; {
        case c == quote && (quote == '\'' || quote == '"'):
                err = ErrSyntax