Why this program not working

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1

Why variable y not working at package level
But z working at function level

package main

var y [2000000000 + 1]byte

func main() {
	        
       var z [2000000000 + 1]byte
         	_ = z
}
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2

hello and welcome to the community.

Can you exaplin better what do you mean with “y not working at package level”? and “z working at function level?”

3

This variation of @10IN_ALL’s code runs on my MacBook Air with no errors:

package main
    var y [2000000000]byte

func main() {  
    var z [2000000000 + 1]byte
    _ = z
}

However, this results in an error:

package main
    var y [2000000000 + 1]byte

func main() {  
    var z [2000000000]byte
    _ = z
}

Here’s the error:

./all.go:2:9: main.y: symbol too large (2000000001 bytes > 2000000000 bytes)

It appears that within the main function, it is OK to create the variable z with
size 2000000000 + 1. However, outside the function, attempting to create y, instead, with that same size causes the error.

I am just beginning to learn Go, and also am puzzled about this.

4

It looks like it’s a linker limitation. This discussion seems relevant.
https://groups.google.com/g/golang-nuts/c/mw5f2kyEjpA

The check appears here https://github.com/golang/go/blob/3fb1d95149fa280343581a48547c3c3f70dac5fb/src/cmd/internal/obj/objfile.go#L394

	if s.Size > cutoff {
		w.ctxt.Diag("%s: symbol too large (%d bytes > %d bytes)", s.Name, s.Size, cutoff)
	}

The constant cutoff is defined at line 307.

const cutoff = int64(2e9) // 2 GB (or so; looks better in errors than 2^31)

2e9 is 2,000,000,000

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