Home > Backend Development > Golang > Why Does Using `% v` in a Nested Struct\'s `String()` Method Lead to a Stack Overflow?

Why Does Using `% v` in a Nested Struct\'s `String()` Method Lead to a Stack Overflow?

Mary-Kate Olsen
Release: 2024-11-04 12:20:02
Original
985 people have browsed it

Why Does Using `% v` in a Nested Struct's `String()` Method Lead to a Stack Overflow?

Recursive Printing Error in Nested Struct String() Method

This question explores the issue of stack overflow when attempting to print a nested struct using the String() method with the % v format specifier.

Problem:

A user attempts to return nested struct elements in the String() method using the following code:

<code class="go">func (c ConfigOne) String() string {
    return fmt.Sprintf("%+v\n", c)
}</code>
Copy after login

When the user tries to print the struct using Logger.Infoln(c.String()), they encounter the error:

runtime: goroutine stack exceeds 1000000000-byte limit
fatal error: stack overflow
Copy after login

Explanation:

The %v and % v formats use the value of String() if the type implements it. Therefore, using % v on a type within the String() function for that type causes infinite recursion.

In this case, the String() method calls fmt.Sprintf("% v", c), which calls the String() method recursively on the embedded Daemon struct, and so on. This leads to an infinite loop and stack overflow.

Solution:

To overcome this issue, the user should not use % v in the String() function. Instead, they should construct their own string, showing the contents of the structure in whatever way they see fit. For example:

<code class="go">func (c ConfigOne) String() string {
    return fmt.Sprintf("Loglevel: %d, Logfile: %s\n", c.Daemon.Loglevel, c.Daemon.Logfile)
}</code>
Copy after login

The above is the detailed content of Why Does Using `% v` in a Nested Struct\'s `String()` Method Lead to a Stack Overflow?. For more information, please follow other related articles on the PHP Chinese website!

source:php.cn
Statement of this Website
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
Latest Articles by Author
Popular Tutorials
More>
Latest Downloads
More>
Web Effects
Website Source Code
Website Materials
Front End Template