Pada Thu, 1 Sep 2016 21:10:44 +0200
Harald Weidner <[email protected]> menulis:
> Hello,
>
> On Thu, Sep 01, 2016 at 01:59:12AM -0700, Muhammad Shulhan wrote:
>
> > > type Slices []string
> > >
> > > func (sl *Slices) String() string {
> > > return fmt.Sprint(sl)
> > > }
>
> > runtime: goroutine stack exceeds 250000000-byte limit
> > fatal error: stack overflow
>
> It is always dangerous to call fmt.Sprint() (or any other print
> method of the fmt package) from a String() method of a value that
> implements the Stringer interface. fmt.Sprint() might call the
> String() method itselfes, which leads to infinite recursion.
>
> From the fmt documentation (https://golang.org/pkg/fmt/#pkg-overview):
>
> | [...]
> | 5. 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).
>
> Wether this happens or not depends on the concrete execution path of
> fmt.Sprint(). Even if three of your four exampes work, I guess they
> could fail with future implementations of the fmt package.
>
> You should always pass basic types to fmt.Sprint(), e.g.
>
> func (sl *Slices) String() string {
> return fmt.Sprint([]string(*sl))
> }
>
> Again, from the fmt documentation:
>
> | To avoid recursion in cases such as
> |
> | type X string
> | func (x X) String() string { return Sprintf("<%s>", x) }
> |
> | convert the value before recurring:
> |
> | func (x X) String() string { return Sprintf("<%s>", string(x)) }
> |
> | Infinite recursion can also be triggered by self-referential data
> | structures, such as a slice that contains itself as an element, if
> that type | has a String method. Such pathologies are rare, however,
> and the package | does not protect against them.
>
> Harald
>
Ah, I see. Thank you Harald, for pointing and explaining the cause. I
must learn to RTFM thoroughly. My mistake.
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