How Do Goroutines Handle Function Return Values?

Understanding Return Values in Goroutines

In Go, goroutines are lightweight concurrency primitives that run concurrently with the main program. When a goroutine invokes a function that returns a value, the question arises: where does the returned value go?

Function Return Values on the Stack

The Go assembly output reveals that return values from functions called within goroutines are stored on the stack. In the example function getNumber(), the return value i is stored on the stack as seen in the assembly code:

0x000a 00010 (z.go:6)   RET ,

Inaccessibility of Return Values from Goroutines

However, this stored return value is not accessible outside the goroutine. This is due to the fact that goroutines run on separate stacks that are destroyed when the goroutine completes its execution. As a result, any data stored on the goroutine's stack becomes inaccessible after the goroutine terminates.

Avoiding Return Values in Goroutines

Due to the inaccessibility of return values from goroutines, it is generally recommended to avoid using return values in functions that are invoked as goroutines. Instead, consider using alternative communication mechanisms such as channels or shared memory to pass data between goroutines.

Conclusion

Return values in goroutines are stored on the goroutine's stack, but they cannot be accessed outside the goroutine. Therefore, it is advisable to avoid using return values in functions that are invoked as goroutines and instead employ other communication mechanisms to share data between goroutines.

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