Imported Upstream version 1.3upstream/1.3

5 files changed, 342 insertions, 152 deletions

diff --git a/src/pkg/fmt/doc.go b/src/pkg/fmt/doc.go
index 095fd03b2..02642d6ae 100644
--- a/src/pkg/fmt/doc.go
+++ b/src/pkg/fmt/doc.go
@@ -37,6 +37,7 @@
 		%e	scientific notation, e.g. -1234.456e+78
 		%E	scientific notation, e.g. -1234.456E+78
 		%f	decimal point but no exponent, e.g. 123.456
+		%F	synonym for %f
 		%g	whichever of %e or %f produces more compact output
 		%G	whichever of %E or %f produces more compact output
 	String and slice of bytes:
@@ -50,23 +51,39 @@
 	There is no 'u' flag.  Integers are printed unsigned if they have unsigned type.
 	Similarly, there is no need to specify the size of the operand (int8, int64).
 
-	The width and precision control formatting and are in units of Unicode
-	code points.  (This differs from C's printf where the units are numbers
+	Width is specified by an optional decimal number immediately following the verb.
+	If absent, the width is whatever is necessary to represent the value.
+	Precision is specified after the (optional) width by a period followed by a
+	decimal number. If no period is present, a default precision is used.
+	A period with no following number specifies a precision of zero.
+	Examples:
+		%f:    default width, default precision
+		%9f    width 9, default precision
+		%.2f   default width, precision 2
+		%9.2f  width 9, precision 2
+		%9.f   width 9, precision 0
+
+	Width and precision are measured in units of Unicode code points.
+	(This differs from C's printf where the units are numbers
 	of bytes.) Either or both of the flags may be replaced with the
 	character '*', causing their values to be obtained from the next
 	operand, which must be of type int.
 
-	For numeric values, width sets the minimum width of the field and
+	For most values, width is the minimum number of characters to output,
+	padding the formatted form with spaces if necessary.
+	For strings, precision is the maximum number of characters to output,
+	truncating if necessary.
+
+	For floating-point values, width sets the minimum width of the field and
 	precision sets the number of places after the decimal, if appropriate,
 	except that for %g/%G it sets the total number of digits. For example,
 	given 123.45 the format %6.2f prints 123.45 while %.4g prints 123.5.
 	The default precision for %e and %f is 6; for %g it is the smallest
 	number of digits necessary to identify the value uniquely.
 
-	For most values, width is the minimum number of characters to output,
-	padding the formatted form with spaces if necessary.
-	For strings, precision is the maximum number of characters to output,
-	truncating if necessary.
+	For complex numbers, the width and precision apply to the two
+	components independently and the result is parenthesized, so %f applied
+	to 1.2+3.4i produces (1.200000+3.400000i).
 
 	Other flags:
 		+	always print a sign for numeric values;
@@ -98,20 +115,33 @@
 		fmt.Printf("%v\n", i)
 	will print 23.
 
-	If an operand implements interface Formatter, that interface
-	can be used for fine control of formatting.
+	Except when printed using the verbs %T and %p, special
+	formatting considerations apply for operands that implement
+	certain interfaces. In order of application:
+
+	1. If an operand implements the Formatter interface, it will
+	be invoked. Formatter provides fine control of formatting.
+
+	2. If the %v verb is used with the # flag (%#v) and the operand
+	implements the GoStringer interface, that will be invoked.
 
 	If the format (which is implicitly %v for Println etc.) is valid
-	for a string (%s %q %v %x %X), the following two rules also apply:
+	for a string (%s %q %v %x %X), the following two rules apply:
 
-	1. If an operand implements the error interface, the Error method
-	will be used to convert the object to a string, which will then
+	3. If an operand implements the error interface, the Error method
+	will be invoked to convert the object to a string, which will then
 	be formatted as required by the verb (if any).
 
-	2. If an operand implements method String() string, that method
-	will be used to convert the object to a string, which will then
+	4. If an operand implements method String() string, that method
+	will be invoked to convert the object to a string, which will then
 	be formatted as required by the verb (if any).
 
+	For compound operands such as slices and structs, the format
+	applies to the elements of each operand, recursively, not to the
+	operand as a whole. Thus %q will quote each element of a slice
+	of strings, and %6.2f will control formatting for each element
+	of a floating-point array.
+
 	To avoid recursion in cases such as
 		type X string
 		func (x X) String() string { return Sprintf("<%s>", x) }
diff --git a/src/pkg/fmt/fmt_test.go b/src/pkg/fmt/fmt_test.go
index bf50675f5..7e3d06b9f 100644
--- a/src/pkg/fmt/fmt_test.go
+++ b/src/pkg/fmt/fmt_test.go
@@ -220,6 +220,12 @@ var fmtTests = []struct {
 	{"%+.3e", 0.0, "+0.000e+00"},
 	{"%+.3e", 1.0, "+1.000e+00"},
 	{"%+.3f", -1.0, "-1.000"},
+	{"%+.3F", -1.0, "-1.000"},
+	{"%+.3F", float32(-1.0), "-1.000"},
+	{"%+07.2f", 1.0, "+001.00"},
+	{"%+07.2f", -1.0, "-001.00"},
+	{"%+10.2f", +1.0, "     +1.00"},
+	{"%+10.2f", -1.0, "     -1.00"},
 	{"% .3E", -1.0, "-1.000E+00"},
 	{"% .3e", 1.0, " 1.000e+00"},
 	{"%+.3g", 0.0, "+0"},
@@ -239,6 +245,8 @@ var fmtTests = []struct {
 	{"%+.3g", 1 + 2i, "(+1+2i)"},
 	{"%.3e", 0i, "(0.000e+00+0.000e+00i)"},
 	{"%.3f", 0i, "(0.000+0.000i)"},
+	{"%.3F", 0i, "(0.000+0.000i)"},
+	{"%.3F", complex64(0i), "(0.000+0.000i)"},
 	{"%.3g", 0i, "(0+0i)"},
 	{"%.3e", 1 + 2i, "(1.000e+00+2.000e+00i)"},
 	{"%.3f", 1 + 2i, "(1.000+2.000i)"},
@@ -397,6 +405,8 @@ var fmtTests = []struct {
 	{"%#v", "foo", `"foo"`},
 	{"%#v", barray, `[5]fmt_test.renamedUint8{0x1, 0x2, 0x3, 0x4, 0x5}`},
 	{"%#v", bslice, `[]fmt_test.renamedUint8{0x1, 0x2, 0x3, 0x4, 0x5}`},
+	{"%#v", []byte(nil), "[]byte(nil)"},
+	{"%#v", []int32(nil), "[]int32(nil)"},
 
 	// slices with other formats
 	{"%#x", []int{1, 2, 15}, `[0x1 0x2 0xf]`},
@@ -495,18 +505,85 @@ var fmtTests = []struct {
 	{"%v", map[float64]int{math.NaN(): 1, math.NaN(): 2}, "map[NaN:<nil> NaN:<nil>]"},
 
 	// Used to crash because nByte didn't allow for a sign.
-	{"%b", int64(-1 << 63), "-1000000000000000000000000000000000000000000000000000000000000000"},
+	{"%b", int64(-1 << 63), zeroFill("-1", 63, "")},
 
 	// Used to panic.
-	{"%0100d", 1, "0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001"},
-	{"%0100d", -1, "-000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001"},
-	{"%0.100f", 1.0, "1.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"},
-	{"%0.100f", -1.0, "-1.0000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"},
+	{"%0100d", 1, zeroFill("", 100, "1")},
+	{"%0100d", -1, zeroFill("-", 99, "1")},
+	{"%0.100f", 1.0, zeroFill("1.", 100, "")},
+	{"%0.100f", -1.0, zeroFill("-1.", 100, "")},
+
+	// Comparison of padding rules with C printf.
+	/*
+		C program:
+		#include <stdio.h>
+
+		char *format[] = {
+			"[%.2f]",
+			"[% .2f]",
+			"[%+.2f]",
+			"[%7.2f]",
+			"[% 7.2f]",
+			"[%+7.2f]",
+			"[%07.2f]",
+			"[% 07.2f]",
+			"[%+07.2f]",
+		};
+
+		int main(void) {
+			int i;
+			for(i = 0; i < 9; i++) {
+				printf("%s: ", format[i]);
+				printf(format[i], 1.0);
+				printf(" ");
+				printf(format[i], -1.0);
+				printf("\n");
+			}
+		}
 
-	// Zero padding floats used to put the minus sign in the middle.
-	{"%020f", -1.0, "-000000000001.000000"},
+		Output:
+			[%.2f]: [1.00] [-1.00]
+			[% .2f]: [ 1.00] [-1.00]
+			[%+.2f]: [+1.00] [-1.00]
+			[%7.2f]: [   1.00] [  -1.00]
+			[% 7.2f]: [   1.00] [  -1.00]
+			[%+7.2f]: [  +1.00] [  -1.00]
+			[%07.2f]: [0001.00] [-001.00]
+			[% 07.2f]: [ 001.00] [-001.00]
+			[%+07.2f]: [+001.00] [-001.00]
+	*/
+	{"%.2f", 1.0, "1.00"},
+	{"%.2f", -1.0, "-1.00"},
+	{"% .2f", 1.0, " 1.00"},
+	{"% .2f", -1.0, "-1.00"},
+	{"%+.2f", 1.0, "+1.00"},
+	{"%+.2f", -1.0, "-1.00"},
+	{"%7.2f", 1.0, "   1.00"},
+	{"%7.2f", -1.0, "  -1.00"},
+	{"% 7.2f", 1.0, "   1.00"},
+	{"% 7.2f", -1.0, "  -1.00"},
+	{"%+7.2f", 1.0, "  +1.00"},
+	{"%+7.2f", -1.0, "  -1.00"},
+	{"%07.2f", 1.0, "0001.00"},
+	{"%07.2f", -1.0, "-001.00"},
+	{"% 07.2f", 1.0, " 001.00"},
+	{"% 07.2f", -1.0, "-001.00"},
+	{"%+07.2f", 1.0, "+001.00"},
+	{"%+07.2f", -1.0, "-001.00"},
+
+	// Complex numbers: exhaustively tested in TestComplexFormatting.
+	{"%7.2f", 1 + 2i, "(   1.00  +2.00i)"},
+	{"%+07.2f", -1 - 2i, "(-001.00-002.00i)"},
+	// Zero padding does not apply to infinities.
+	{"%020f", math.Inf(-1), "                -Inf"},
+	{"%020f", math.Inf(+1), "                +Inf"},
+	{"% 020f", math.Inf(-1), "                -Inf"},
+	{"% 020f", math.Inf(+1), "                 Inf"},
+	{"%+020f", math.Inf(-1), "                -Inf"},
+	{"%+020f", math.Inf(+1), "                +Inf"},
 	{"%20f", -1.0, "           -1.000000"},
-	{"%0100f", -1.0, "-00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000001.000000"},
+	// Make sure we can handle very large widths.
+	{"%0100f", -1.0, zeroFill("-", 99, "1.000000")},
 
 	// Complex fmt used to leave the plus flag set for future entries in the array
 	// causing +2+0i and +3+0i instead of 2+0i and 3+0i.
@@ -515,6 +592,43 @@ var fmtTests = []struct {
 
 	// Incomplete format specification caused crash.
 	{"%.", 3, "%!.(int=3)"},
+
+	// Used to panic with out-of-bounds for very large numeric representations.
+	// nByte is set to handle one bit per uint64 in %b format, with a negative number.
+	// See issue 6777.
+	{"%#064x", 1, zeroFill("0x", 64, "1")},
+	{"%#064x", -1, zeroFill("-0x", 63, "1")},
+	{"%#064b", 1, zeroFill("", 64, "1")},
+	{"%#064b", -1, zeroFill("-", 63, "1")},
+	{"%#064o", 1, zeroFill("", 64, "1")},
+	{"%#064o", -1, zeroFill("-", 63, "1")},
+	{"%#064d", 1, zeroFill("", 64, "1")},
+	{"%#064d", -1, zeroFill("-", 63, "1")},
+	// Test that we handle the crossover above the size of uint64
+	{"%#072x", 1, zeroFill("0x", 72, "1")},
+	{"%#072x", -1, zeroFill("-0x", 71, "1")},
+	{"%#072b", 1, zeroFill("", 72, "1")},
+	{"%#072b", -1, zeroFill("-", 71, "1")},
+	{"%#072o", 1, zeroFill("", 72, "1")},
+	{"%#072o", -1, zeroFill("-", 71, "1")},
+	{"%#072d", 1, zeroFill("", 72, "1")},
+	{"%#072d", -1, zeroFill("-", 71, "1")},
+
+	// Padding for complex numbers. Has been bad, then fixed, then bad again.
+	{"%+10.2f", +104.66 + 440.51i, "(   +104.66   +440.51i)"},
+	{"%+10.2f", -104.66 + 440.51i, "(   -104.66   +440.51i)"},
+	{"%+10.2f", +104.66 - 440.51i, "(   +104.66   -440.51i)"},
+	{"%+10.2f", -104.66 - 440.51i, "(   -104.66   -440.51i)"},
+	{"%+010.2f", +104.66 + 440.51i, "(+000104.66+000440.51i)"},
+	{"%+010.2f", -104.66 + 440.51i, "(-000104.66+000440.51i)"},
+	{"%+010.2f", +104.66 - 440.51i, "(+000104.66-000440.51i)"},
+	{"%+010.2f", -104.66 - 440.51i, "(-000104.66-000440.51i)"},
+}
+
+// zeroFill generates zero-filled strings of the specified width. The length
+// of the suffix (but not the prefix) is compensated for in the width calculation.
+func zeroFill(prefix string, width int, suffix string) string {
+	return prefix + strings.Repeat("0", width-len(suffix)) + suffix
 }
 
 func TestSprintf(t *testing.T) {
@@ -554,6 +668,50 @@ func TestSprintf(t *testing.T) {
 	}
 }
 
+// TestComplexFormatting checks that a complex always formats to the same
+// thing as if done by hand with two singleton prints.
+func TestComplexFormatting(t *testing.T) {
+	var yesNo = []bool{true, false}
+	var signs = []float64{1, 0, -1}
+	for _, plus := range yesNo {
+		for _, zero := range yesNo {
+			for _, space := range yesNo {
+				for _, char := range "fFeEgG" {
+					realFmt := "%"
+					if zero {
+						realFmt += "0"
+					}
+					if space {
+						realFmt += " "
+					}
+					if plus {
+						realFmt += "+"
+					}
+					realFmt += "10.2"
+					realFmt += string(char)
+					// Imaginary part always has a sign, so force + and ignore space.
+					imagFmt := "%"
+					if zero {
+						imagFmt += "0"
+					}
+					imagFmt += "+"
+					imagFmt += "10.2"
+					imagFmt += string(char)
+					for _, realSign := range signs {
+						for _, imagSign := range signs {
+							one := Sprintf(realFmt, complex(realSign, imagSign))
+							two := Sprintf("("+realFmt+imagFmt+"i)", realSign, imagSign)
+							if one != two {
+								t.Error(f, one, two)
+							}
+						}
+					}
+				}
+			}
+		}
+	}
+}
+
 type SE []interface{} // slice of empty; notational compactness.
 
 var reorderTests = []struct {
@@ -604,47 +762,61 @@ func TestReorder(t *testing.T) {
 }
 
 func BenchmarkSprintfEmpty(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		Sprintf("")
-	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("")
+		}
+	})
 }
 
 func BenchmarkSprintfString(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		Sprintf("%s", "hello")
-	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%s", "hello")
+		}
+	})
 }
 
 func BenchmarkSprintfInt(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		Sprintf("%d", 5)
-	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%d", 5)
+		}
+	})
 }
 
 func BenchmarkSprintfIntInt(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		Sprintf("%d %d", 5, 6)
-	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%d %d", 5, 6)
+		}
+	})
 }
 
 func BenchmarkSprintfPrefixedInt(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		Sprintf("This is some meaningless prefix text that needs to be scanned %d", 6)
-	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("This is some meaningless prefix text that needs to be scanned %d", 6)
+		}
+	})
 }
 
 func BenchmarkSprintfFloat(b *testing.B) {
-	for i := 0; i < b.N; i++ {
-		Sprintf("%g", 5.23184)
-	}
+	b.RunParallel(func(pb *testing.PB) {
+		for pb.Next() {
+			Sprintf("%g", 5.23184)
+		}
+	})
 }
 
 func BenchmarkManyArgs(b *testing.B) {
-	var buf bytes.Buffer
-	for i := 0; i < b.N; i++ {
-		buf.Reset()
-		Fprintf(&buf, "%2d/%2d/%2d %d:%d:%d %s %s\n", 3, 4, 5, 11, 12, 13, "hello", "world")
-	}
+	b.RunParallel(func(pb *testing.PB) {
+		var buf bytes.Buffer
+		for pb.Next() {
+			buf.Reset()
+			Fprintf(&buf, "%2d/%2d/%2d %d:%d:%d %s %s\n", 3, 4, 5, 11, 12, 13, "hello", "world")
+		}
+	})
 }
 
 var mallocBuf bytes.Buffer
diff --git a/src/pkg/fmt/format.go b/src/pkg/fmt/format.go
index 2e2b0716e..a89c542cf 100644
--- a/src/pkg/fmt/format.go
+++ b/src/pkg/fmt/format.go
@@ -5,12 +5,15 @@
 package fmt
 
 import (
+	"math"
 	"strconv"
 	"unicode/utf8"
 )
 
 const (
-	nByte = 65 // %b of an int64, plus a sign.
+	// %b of an int64, plus a sign.
+	// Hex can add 0x and we handle it specially.
+	nByte = 65
 
 	ldigits = "0123456789abcdef"
 	udigits = "0123456789ABCDEF"
@@ -160,9 +163,16 @@ func (f *fmt) integer(a int64, base uint64, signedness bool, digits string) {
 	}
 
 	var buf []byte = f.intbuf[0:]
-	if f.widPresent && f.wid > nByte {
-		// We're going to need a bigger boat.
-		buf = make([]byte, f.wid)
+	if f.widPresent {
+		width := f.wid
+		if base == 16 && f.sharp {
+			// Also adds "0x".
+			width += 2
+		}
+		if width > nByte {
+			// We're going to need a bigger boat.
+			buf = make([]byte, width)
+		}
 	}
 
 	negative := signedness == signed && a < 0
@@ -351,35 +361,48 @@ func doPrec(f *fmt, def int) int {
 
 // formatFloat formats a float64; it is an efficient equivalent to  f.pad(strconv.FormatFloat()...).
 func (f *fmt) formatFloat(v float64, verb byte, prec, n int) {
-	// We leave one byte at the beginning of f.intbuf for a sign if needed,
-	// and make it a space, which we might be able to use.
-	f.intbuf[0] = ' '
-	slice := strconv.AppendFloat(f.intbuf[0:1], v, verb, prec, n)
-	// Add a plus sign or space to the floating-point string representation if missing and required.
-	// The formatted number starts at slice[1].
-	switch slice[1] {
-	case '-', '+':
-		// If we're zero padding, want the sign before the leading zeros.
-		// Achieve this by writing the sign out and padding the postive number.
-		if f.zero && f.widPresent && f.wid > len(slice) {
-			f.buf.WriteByte(slice[1])
-			f.wid--
-			f.pad(slice[2:])
-			return
+	// Format number, reserving space for leading + sign if needed.
+	num := strconv.AppendFloat(f.intbuf[0:1], v, verb, prec, n)
+	if num[1] == '-' || num[1] == '+' {
+		num = num[1:]
+	} else {
+		num[0] = '+'
+	}
+	// Special handling for infinity, which doesn't look like a number so shouldn't be padded with zeros.
+	if math.IsInf(v, 0) {
+		if f.zero {
+			defer func() { f.zero = true }()
+			f.zero = false
 		}
-		// We're set; drop the leading space.
-		slice = slice[1:]
-	default:
-		// There's no sign, but we might need one.
-		if f.plus {
-			slice[0] = '+'
-		} else if f.space {
-			// space is already there
-		} else {
-			slice = slice[1:]
+	}
+	// num is now a signed version of the number.
+	// If we're zero padding, want the sign before the leading zeros.
+	// Achieve this by writing the sign out and then padding the unsigned number.
+	if f.zero && f.widPresent && f.wid > len(num) {
+		if f.space && v >= 0 {
+			f.buf.WriteByte(' ') // This is what C does: even with zero, f.space means space.
+			f.wid--
+		} else if f.plus || v < 0 {
+			f.buf.WriteByte(num[0])
+			f.wid--
 		}
+		f.pad(num[1:])
+		return
+	}
+	// f.space says to replace a leading + with a space.
+	if f.space && num[0] == '+' {
+		num[0] = ' '
+		f.pad(num)
+		return
 	}
-	f.pad(slice)
+	// Now we know the sign is attached directly to the number, if present at all.
+	// We want a sign if asked for, if it's negative, or if it's infinity (+Inf vs. -Inf).
+	if f.plus || num[0] == '-' || math.IsInf(v, 0) {
+		f.pad(num)
+		return
+	}
+	// No sign to show and the number is positive; just print the unsigned number.
+	f.pad(num[1:])
 }
 
 // fmt_e64 formats a float64 in the form -1.23e+12.
@@ -424,60 +447,46 @@ func (f *fmt) fmt_fb32(v float32) { f.formatFloat(float64(v), 'b', 0, 32) }
 
 // fmt_c64 formats a complex64 according to the verb.
 func (f *fmt) fmt_c64(v complex64, verb rune) {
-	f.buf.WriteByte('(')
-	r := real(v)
-	oldPlus := f.plus
-	for i := 0; ; i++ {
-		switch verb {
-		case 'b':
-			f.fmt_fb32(r)
-		case 'e':
-			f.fmt_e32(r)
-		case 'E':
-			f.fmt_E32(r)
-		case 'f':
-			f.fmt_f32(r)
-		case 'g':
-			f.fmt_g32(r)
-		case 'G':
-			f.fmt_G32(r)
-		}
-		if i != 0 {
-			break
-		}
-		f.plus = true
-		r = imag(v)
-	}
-	f.plus = oldPlus
-	f.buf.Write(irparenBytes)
+	f.fmt_complex(float64(real(v)), float64(imag(v)), 32, verb)
 }
 
 // fmt_c128 formats a complex128 according to the verb.
 func (f *fmt) fmt_c128(v complex128, verb rune) {
+	f.fmt_complex(real(v), imag(v), 64, verb)
+}
+
+// fmt_complex formats a complex number as (r+ji).
+func (f *fmt) fmt_complex(r, j float64, size int, verb rune) {
 	f.buf.WriteByte('(')
-	r := real(v)
 	oldPlus := f.plus
+	oldSpace := f.space
+	oldWid := f.wid
 	for i := 0; ; i++ {
 		switch verb {
 		case 'b':
-			f.fmt_fb64(r)
+			f.formatFloat(r, 'b', 0, size)
 		case 'e':
-			f.fmt_e64(r)
+			f.formatFloat(r, 'e', doPrec(f, 6), size)
 		case 'E':
-			f.fmt_E64(r)
-		case 'f':
-			f.fmt_f64(r)
+			f.formatFloat(r, 'E', doPrec(f, 6), size)
+		case 'f', 'F':
+			f.formatFloat(r, 'f', doPrec(f, 6), size)
 		case 'g':
-			f.fmt_g64(r)
+			f.formatFloat(r, 'g', doPrec(f, -1), size)
 		case 'G':
-			f.fmt_G64(r)
+			f.formatFloat(r, 'G', doPrec(f, -1), size)
 		}
 		if i != 0 {
 			break
 		}
+		// Imaginary part always has a sign.
 		f.plus = true
-		r = imag(v)
+		f.space = false
+		f.wid = oldWid
+		r = j
 	}
+	f.space = oldSpace
 	f.plus = oldPlus
+	f.wid = oldWid
 	f.buf.Write(irparenBytes)
 }
diff --git a/src/pkg/fmt/print.go b/src/pkg/fmt/print.go
index 1ea816d6d..302661f4c 100644
--- a/src/pkg/fmt/print.go
+++ b/src/pkg/fmt/print.go
@@ -124,45 +124,13 @@ type pp struct {
 	fmt        fmt
 }
 
-// A cache holds a set of reusable objects.
-// The slice is a stack (LIFO).
-// If more are needed, the cache creates them by calling new.
-type cache struct {
-	mu    sync.Mutex
-	saved []interface{}
-	new   func() interface{}
+var ppFree = sync.Pool{
+	New: func() interface{} { return new(pp) },
 }
 
-func (c *cache) put(x interface{}) {
-	c.mu.Lock()
-	if len(c.saved) < cap(c.saved) {
-		c.saved = append(c.saved, x)
-	}
-	c.mu.Unlock()
-}
-
-func (c *cache) get() interface{} {
-	c.mu.Lock()
-	n := len(c.saved)
-	if n == 0 {
-		c.mu.Unlock()
-		return c.new()
-	}
-	x := c.saved[n-1]
-	c.saved = c.saved[0 : n-1]
-	c.mu.Unlock()
-	return x
-}
-
-func newCache(f func() interface{}) *cache {
-	return &cache{saved: make([]interface{}, 0, 100), new: f}
-}
-
-var ppFree = newCache(func() interface{} { return new(pp) })
-
 // newPrinter allocates a new pp struct or grab a cached one.
 func newPrinter() *pp {
-	p := ppFree.get().(*pp)
+	p := ppFree.Get().(*pp)
 	p.panicking = false
 	p.erroring = false
 	p.fmt.init(&p.buf)
@@ -178,7 +146,7 @@ func (p *pp) free() {
 	p.buf = p.buf[:0]
 	p.arg = nil
 	p.value = reflect.Value{}
-	ppFree.put(p)
+	ppFree.Put(p)
 }
 
 func (p *pp) Width() (wid int, ok bool) { return p.fmt.wid, p.fmt.widPresent }
@@ -479,7 +447,7 @@ func (p *pp) fmtFloat32(v float32, verb rune) {
 		p.fmt.fmt_e32(v)
 	case 'E':
 		p.fmt.fmt_E32(v)
-	case 'f':
+	case 'f', 'F':
 		p.fmt.fmt_f32(v)
 	case 'g', 'v':
 		p.fmt.fmt_g32(v)
@@ -498,7 +466,7 @@ func (p *pp) fmtFloat64(v float64, verb rune) {
 		p.fmt.fmt_e64(v)
 	case 'E':
 		p.fmt.fmt_E64(v)
-	case 'f':
+	case 'f', 'F':
 		p.fmt.fmt_f64(v)
 	case 'g', 'v':
 		p.fmt.fmt_g64(v)
@@ -555,6 +523,15 @@ func (p *pp) fmtString(v string, verb rune, goSyntax bool) {
 func (p *pp) fmtBytes(v []byte, verb rune, goSyntax bool, typ reflect.Type, depth int) {
 	if verb == 'v' || verb == 'd' {
 		if goSyntax {
+			if v == nil {
+				if typ == nil {
+					p.buf.WriteString("[]byte(nil)")
+				} else {
+					p.buf.WriteString(typ.String())
+					p.buf.Write(nilParenBytes)
+				}
+				return
+			}
 			if typ == nil {
 				p.buf.Write(bytesBytes)
 			} else {
diff --git a/src/pkg/fmt/scan.go b/src/pkg/fmt/scan.go
index 5b1be5891..8a337e479 100644
--- a/src/pkg/fmt/scan.go
+++ b/src/pkg/fmt/scan.go
@@ -11,6 +11,7 @@ import (
 	"os"
 	"reflect"
 	"strconv"
+	"sync"
 	"unicode/utf8"
 )
 
@@ -283,7 +284,6 @@ var space = [][2]uint16{
 	{0x0085, 0x0085},
 	{0x00a0, 0x00a0},
 	{0x1680, 0x1680},
-	{0x180e, 0x180e},
 	{0x2000, 0x200a},
 	{0x2028, 0x2029},
 	{0x202f, 0x202f},
@@ -380,7 +380,9 @@ func (r *readRune) ReadRune() (rr rune, size int, err error) {
 	return
 }
 
-var ssFree = newCache(func() interface{} { return new(ss) })
+var ssFree = sync.Pool{
+	New: func() interface{} { return new(ss) },
+}
 
 // newScanState allocates a new ss struct or grab a cached one.
 func newScanState(r io.Reader, nlIsSpace, nlIsEnd bool) (s *ss, old ssave) {
@@ -395,7 +397,7 @@ func newScanState(r io.Reader, nlIsSpace, nlIsEnd bool) (s *ss, old ssave) {
 		return
 	}
 
-	s = ssFree.get().(*ss)
+	s = ssFree.Get().(*ss)
 	if rr, ok := r.(io.RuneReader); ok {
 		s.rr = rr
 	} else {
@@ -427,7 +429,7 @@ func (s *ss) free(old ssave) {
 	}
 	s.buf = s.buf[:0]
 	s.rr = nil
-	ssFree.put(s)
+	ssFree.Put(s)
 }
 
 // skipSpace skips spaces and maybe newlines.