Go语言中为什么fmt.Fprintln(...)会有告警，而fmt.Println(...)却没有？

用户1392128

发布于 2024-01-08 17:50:12

1450

发布于 2024-01-08 17:50:12

问题描述：

环境：Windows10 + GoLand 2019.3.4 x64 + Golang 现象：在使用fmt包，调用fmt.Fprintln(…)写文件时，如果不接受函数的返回值，编辑器会提示Unhandled error错误而对于fmt.Println(…) 则不会提示

问题分析：

我们来看一下源码

// Fprintln formats using the default formats for its operands and writes to w.
// Spaces are always added between operands and a newline is appended.
// It returns the number of bytes written and any write error encountered.
func Fprintln(w io.Writer, a ...interface{}) (n int, err error) {
	p := newPrinter()
	p.doPrintln(a)
	n, err = w.Write(p.buf)
	p.free()
	return
}

// Println formats using the default formats for its operands and writes to standard output.
// Spaces are always added between operands and a newline is appended.
// It returns the number of bytes written and any write error encountered.
func Println(a ...interface{}) (n int, err error) {
	return Fprintln(os.Stdout, a...)
}

两个函数均有两个返回值：n int, err error

那么为什么会出现上面奇怪的现象呢？为了搞清这个问题，我在flag/print.go中添加了一个同样的函数，区别只是换了个名字Printf2：

// Printf formats according to a format specifier and writes to standard output.
// It returns the number of bytes written and any write error encountered.
func Printf(format string, a ...interface{}) (n int, err error) {
	return Fprintf(os.Stdout, format, a...)
}

// Printf formats according to a format specifier and writes to standard output.
// It returns the number of bytes written and any write error encountered.
func Printf2(format string, a ...interface{}) (n int, err error) {
	return Fprintf(os.Stdout, format, a...)
}

但是，同样的告警还是出现在了Printf2函数上

然而，我在深入研究fmt源码时，却在源码中看到以下示例

func ExampleFprintf() {
	const name, age = "Kim", 22
	n, err := fmt.Fprintf(os.Stdout, "%s is %d years old.\n", name, age)

	// The n and err return values from Fprintf are
	// those returned by the underlying io.Writer.
	if err != nil {
		fmt.Fprintf(os.Stderr, "Fprintf: %v\n", err)
	}
	fmt.Printf("%d bytes written.\n", n)

	// Output:
	// Kim is 22 years old.
	// 21 bytes written.
}

而fmt.Fprintf(os.Stderr, “Fprintf: %v\n”, err)没有接受返回的错误，却没有告警