Why does using `fmt.Println()` instead of `println()` affect stack growth and the addresses of variables in Go?

Mix Printing with fmt.Println and Stack Growth

When utilizing Go's println() and fmt.Println() functions for printing, an odd behavior arises regarding stack growth. Understanding the difference between these two functions is crucial for comprehending this phenomenon.

println() vs. fmt.Println()

println() is an intrinsic function that does not hold onto any arguments passed to it, effectively leaving them on the stack. In contrast, fmt.Println() originates from the standard library and is handled akin to user-defined functions. Consequently, the compiler cannot assume that it does not retain arguments, potentially leading to their allocation on the heap rather than the stack.

Stack Growth

Go employs a dynamic stack that expands as needed. When substantial data is passed to a recursive function, the initial stack size may prove insufficient, necessitating the allocation of a larger stack. This expansion causes stack-allocated variables to be relocated, modifying their addresses.

Influence on Address Values

When println() is exclusively employed, the stack growth mechanism prompts the address of the "s" string to change because the data is moved to a different location. However, using fmt.Println(), the address of "s" remains constant since the compiler anticipates its potential escape to the heap, hence allocating it on the heap rather than the stack.

Escape Analysis

The compiler performs escape analysis to determine whether arguments passed to functions might be stored beyond their initial scope. The results of this analysis can be viewed by utilizing the "-gcflags '-m'" flag during compilation.

When only println() is used, the compiler identifies "s" as not escaping, which means it remains on the stack. However, when fmt.Println() is incorporated, the compiler concludes that "s" could potentially escape and allocates it on the heap.

The above is the detailed content of Why does using `fmt.Println()` instead of `println()` affect stack growth and the addresses of variables in Go?. For more information, please follow other related articles on the PHP Chinese website!