cmd/compile: large arrays cause large binaries and toolchain errors

[crawshaw]

On tip, go version devel +0db9518 Fri Oct 7 03:46:50 2016 +0000 darwin/amd64:

$ cat j.go 
package main

var x = [1 << 30]byte{0: 1}

func main() {
    println(x[0])
}
$ go build j.go
$ ls -l j
-rwxr-xr-x  1 crawshaw  eng  1074669392 Oct  7 10:34 j

Bumping 1<<30 to 1<<31 turns it into a linker error:

~$ go build j.go 
# command-line-arguments
main.x: symbol too large (2147483648 bytes)
too much data in section SNOPTRDATA (over 2000000000 bytes)
too much data in section SDATA (over 2000000000 bytes)
too much data in section SBSS (over 2000000000 bytes)
too much data in section SNOPTRBSS (over 2000000000 bytes)
main.init: pc-relative relocation address for main.initdone· is too big: 0x800ad36a
main.init: pc-relative relocation address for main.initdone· is too big: 0x800ad355
runtime.alginit: pc-relative relocation address for runtime.cpuid_ecx is too big: 0x800ac585
runtime.alginit: pc-relative relocation address for runtime.hashkey is too big: 0x800ac72d
runtime.alginit: pc-relative relocation address for runtime.hashkey is too big: 0x800ac70b
runtime.alginit: pc-relative relocation address for runtime.hashkey is too big: 0x800ac700
runtime.alginit: pc-relative relocation address for runtime.hashkey is too big: 0x800ac701
runtime.alginit: pc-relative relocation address for runtime.hashkey is too big: 0x800ac6f6
runtime.alginit: pc-relative relocation address for runtime.hashkey is too big: 0x800ac6f7
runtime.alginit: pc-relative relocation address for runtime.hashkey is too big: 0x800ac6ec
runtime.alginit: pc-relative relocation address for runtime.hashkey is too big: 0x800ac6ed
runtime.alginit: pc-relative relocation address for runtime.hashkey is too big: 0x800ac6e2
runtime.alginit: pc-relative relocation address for runtime.useAeshash is too big: 0x800ac4ea
runtime.alginit: pc-relative relocation address for runtime.algarray is too big: 0x80091a0b
runtime.alginit: pc-relative relocation address for runtime.algarray is too big: 0x80091a0d
runtime.alginit: pc-relative relocation address for runtime.algarray is too big: 0x80091a1f
/Users/crawshaw/go/pkg/tool/darwin_amd64/link: too many errors

(Inspired by https://codegolf.stackexchange.com/questions/69189/build-a-compiler-bomb/69193#69193)

[mrjrieke]

I wonder how compiler behaves if allocate is inside main?

[ALTree]

Isn't this on purpose? The message was introduced in commit cmd/link: reject data size > 2 GB to fix issue #9862

[mrjrieke]

True Alberto. Although, does golint help identify the line number with the
problem? Seems like something either the compiler or one of the tools
should be able to identify more precisely the source of the problem.

On Fri, Oct 7, 2016 at 9:52 AM, Alberto Donizetti notifications@github.com
wrote:

Isn't this on purpose? The message was introduced in commit cmd/link:
reject data size > 2 GB to fix issue #9862
#9862

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