How to Preserve Original Memory Addresses When Converting a Go Slice of Strings to a Slice of String Pointers?

Preserving Identifier Address in Slice Conversion

In Go, converting a slice of strings (values1) to a slice of pointers to strings (values2) presents a unique challenge. The code provided below illustrates the issue:

values1 := []string{"a", "b", "c"}
var values2 []*string
for _, v := range values1 {
    fmt.Printf("%p | %T\n", v, v)
    values2 = append(values2, &v)
}

Expectedly, the output reveals that each element in values2 points to the same memory address, despite having different values. This occurs because the range loop variable v is a copy of the original string value, not a pointer to it. As a result, v remains a string value, even when assigned a new value within the loop.

Solution Implementation

To resolve this issue, we must append the address of the original slice elements to values2. Here are two possible solutions:

1. Indexing the Original Slice

for i, _ := range values1 {
    values2 = append(values2, &values1[i])
}

By accessing the slice elements through indexing, we obtain the desired pointer addresses and preserve their distinct values.

2. Using Temporary Variables

for _, v := range values1 {
    v2 := v
    values2 = append(values2, &v2)
}

In this approach, we declare a temporary variable (v2) to hold each string value. By assigning v2 to &v2, we create an independent pointer value that ensures values2 contains unique pointers.

Implications of Preserving Identifier Address

It's important to note that preserving the identifier addresses has certain implications:

• The backing array of values1 is retained in memory as long as both values1 and values2 are reachable.
• Modifications to values1 elements will be reflected in values2.
• To prevent values1 from being garbage collected, either use indexing or temporary variables, as described in the solutions above.

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