fmt: allow any type in a format's width argument
The construction
fmt.Printf("%*d", n, 4)
reads the argument n as a width specifier to use when printing 4.
Until now, only strict int type was accepted here and it couldn't
be fixed because the fix, using reflection, broke escape analysis
and added an extra allocation in every Printf call, even those that
do not use this feature.
The compiler has been fixed, although I am not sure when exactly,
so let's fix Printf and then write
Fixes #10732.
Change-Id: I79cf0c4fadd876265aa39d3cb62867247b36ab65
Reviewed-on: https://go-review.googlesource.com/14491
Reviewed-by: Ian Lance Taylor <iant@golang.org>
diff --git a/src/fmt/fmt_test.go b/src/fmt/fmt_test.go
index 90a4031..26383f6 100644
--- a/src/fmt/fmt_test.go
+++ b/src/fmt/fmt_test.go
@@ -1188,6 +1188,11 @@
{"%.*d", args(4, 42), "0042"},
{"%*.*d", args(8, 4, 42), " 0042"},
{"%0*d", args(4, 42), "0042"},
+ // Some non-int types for width. (Issue 10732).
+ {"%0*d", args(uint(4), 42), "0042"},
+ {"%0*d", args(uint64(4), 42), "0042"},
+ {"%0*d", args('\x04', 42), "0042"},
+ {"%0*d", args(uintptr(4), 42), "0042"},
// erroneous
{"%*d", args(nil, 42), "%!(BADWIDTH)42"},
@@ -1196,17 +1201,19 @@
{"%.*d", args(nil, 42), "%!(BADPREC)42"},
{"%.*d", args(-1, 42), "%!(BADPREC)42"},
{"%.*d", args(int(1e7), 42), "%!(BADPREC)42"},
+ {"%.*d", args(uint(1e7), 42), "%!(BADPREC)42"},
+ {"%.*d", args(uint64(1<<63), 42), "%!(BADPREC)42"}, // Huge negative (-inf).
+ {"%.*d", args(uint64(1<<64-1), 42), "%!(BADPREC)42"}, // Small negative (-1).
{"%*d", args(5, "foo"), "%!d(string= foo)"},
{"%*% %d", args(20, 5), "% 5"},
{"%*", args(4), "%!(NOVERB)"},
- {"%*d", args(int32(4), 42), "%!(BADWIDTH)42"},
}
func TestWidthAndPrecision(t *testing.T) {
- for _, tt := range startests {
+ for i, tt := range startests {
s := Sprintf(tt.fmt, tt.in...)
if s != tt.out {
- t.Errorf("%q: got %q expected %q", tt.fmt, s, tt.out)
+ t.Errorf("#%d: %q: got %q expected %q", i, tt.fmt, s, tt.out)
}
}
}
diff --git a/src/fmt/print.go b/src/fmt/print.go
index 8d3e97c..ebfa13e 100644
--- a/src/fmt/print.go
+++ b/src/fmt/print.go
@@ -1024,11 +1024,30 @@
return wasString
}
-// intFromArg gets the argNumth element of a. On return, isInt reports whether the argument has type int.
+// intFromArg gets the argNumth element of a. On return, isInt reports whether the argument has integer type.
func intFromArg(a []interface{}, argNum int) (num int, isInt bool, newArgNum int) {
newArgNum = argNum
if argNum < len(a) {
- num, isInt = a[argNum].(int)
+ num, isInt = a[argNum].(int) // Almost always OK.
+ if !isInt {
+ // Work harder.
+ switch v := reflect.ValueOf(a[argNum]); v.Kind() {
+ case reflect.Int, reflect.Int8, reflect.Int16, reflect.Int32, reflect.Int64:
+ n := v.Int()
+ if int64(int(n)) == n {
+ num = int(n)
+ isInt = true
+ }
+ case reflect.Uint, reflect.Uint8, reflect.Uint16, reflect.Uint32, reflect.Uint64, reflect.Uintptr:
+ n := v.Uint()
+ if int64(n) >= 0 && uint64(int(n)) == n {
+ num = int(n)
+ isInt = true
+ }
+ default:
+ // Already 0, false.
+ }
+ }
newArgNum = argNum + 1
if tooLarge(num) {
num = 0
