handle nils safely in Printf.

add some tests for erroneous formats.

R=rsc
CC=golang-dev
https://golang.org/cl/201058

diff --git a/src/pkg/fmt/fmt_test.go b/src/pkg/fmt/fmt_test.go
index ecceeb09cec65b4ba55ec7c8f4738a950658ccb3..9fdf0ddb36408f771ae745ab2bc88d9618c800a6 100644 (file)
--- a/src/pkg/fmt/fmt_test.go
+++ b/src/pkg/fmt/fmt_test.go
@@ -229,6 +229,11 @@ var fmttests = []fmtTest{
        fmtTest{"%#v", make(chan int), "(chan int)(PTR)"},
        fmtTest{"%#v", uint64(1<<64 - 1), "0xffffffffffffffff"},
        fmtTest{"%#v", 1000000000, "1000000000"},
+
+       // erroneous things
+       fmtTest{"%d", "hello", "%d(string=hello)"},
+       fmtTest{"no args", "hello", "no args?(extra string=hello)"},
+       fmtTest{"%s", nil, "%s(<nil>)"},
 }
 
 func TestSprintf(t *testing.T) {

diff --git a/src/pkg/fmt/print.go b/src/pkg/fmt/print.go
index de64179cc876f69e104f799287b80ee20a2291e6..e4840b940bb688c7de582a767a58c82c691c5091 100644 (file)
--- a/src/pkg/fmt/print.go
+++ b/src/pkg/fmt/print.go
@@ -378,6 +378,9 @@ func getInt(a interface{}) (val int64, signed, ok bool) {
 }
 
 func getString(a interface{}) (val string, ok bool) {
+       if a == nil {
+               return "<nil>", ok
+       }
        // Is it a regular string or []byte type?
        switch s := a.(type) {
        case string:
@@ -941,8 +944,10 @@ func (p *pp) doprintf(format string, a []interface{}) {
                        p.buf.WriteByte('%')
                        p.add(c)
                        p.buf.WriteByte('(')
-                       p.buf.WriteString(reflect.Typeof(field).String())
-                       p.buf.WriteByte('=')
+                       if field != nil {
+                               p.buf.WriteString(reflect.Typeof(field).String())
+                               p.buf.WriteByte('=')
+                       }
                        p.printField(field, false, false, 0)
                        p.buf.WriteByte(')')
                }