## When and Why Should You Avoid `unsafe` Conversion from `[]byte` to `string` in Go?

Handling Unsafe Conversion from []byte to String in Go

In Go, the preferred method for converting a byte slice ([]byte) to a string is:

<code class="go">var b []byte
// fill b
s := string(b)</code>

This approach facilitates byte slice copying, which might prove problematic in performance-critical situations.

However, for such scenarios, an unsafe conversion can be considered:

<code class="go">var b []byte
// fill b
s :=  *(*string)(unsafe.Pointer(&amp;b))</code>

Consequences of Unsafe Conversion

While unsafe conversion can indeed enhance performance, it risks violating the immutability guarantee of strings in Go. Modifying a string that the language specification expects to be immutable can lead to unexpected behavior. The following are some potential consequences:

• Invalidation of Cache Optimizations: Compilers are authorized to cache strings they know to be immutable, which allows for code optimization. Unsafe conversion removes this guarantee, potentially resulting in reduced efficiency.
• Unpredictable Behavior in Data Structures: In data structures like maps and sets, keys are typically strings. When a modified string's hash code changes, it may be moved to a different bucket within the structure. This can render the key unsearchable, even when using the original string value. Consider the following example:

<code class="go">m := map[string]int{}
b := []byte("hi")
s := *(*string)(unsafe.Pointer(&amp;b))
m[s] = 999

fmt.Println("Before:", m)

b[0] = 'b'
fmt.Println("After:", m)

fmt.Println("But it's there:", m[s], m["bi"])

for i := 0; i < 1000; i++ {
    m[strconv.Itoa(i)] = i
}
fmt.Println("Now it's GONE:", m[s], m["bi"])
for k, v := range m {
    if k == "bi" {
        fmt.Println("But still there, just in a different bucket: ", k, v)
    }
}</code>

After modifying the string's first byte to 'b', it becomes unfindable using either the original or modified key. However, the modified string still exists in the map, albeit in a different bucket.

• Non-Portability of Code: Code that utilizes the unsafe package is platform-dependent and does not comply with Go's compatibility guidelines. Therefore, it may not function as intended in future or previous versions of Go.
• Unanticipated Errors: Modifying a string using unsafe conversion can lead to unforeseen errors because the modified string may be used in various ways. For instance, copying the string header or its content can result in unexpected behavior.

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