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cmd/link: reject >2GB static data #9862

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randall77 opened this issue Feb 13, 2015 · 5 comments
Closed

cmd/link: reject >2GB static data #9862

randall77 opened this issue Feb 13, 2015 · 5 comments
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Go1.5

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@randall77
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The following code prints 2!

package main
var a[1<<31]byte
func main() {
     println(a[0])
}

It seems that when bss is big, bad things happen on darwin. At 1<<30, it works (prints 0). It also fails at 1<<31, 1<<32, 1<<33. We get a compile error at 1<<31 - 1:

runtime.mallocinit: non-pc-relative relocation address is too big: 0x80070dbf

We should fail instead of silently generating bad code.

Linux works correctly: succeeds for up to close to 1<<32, fails with the above error for larger sizes.
@bradfitz bradfitz added this to the Go1.5 milestone Feb 13, 2015
@minux
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minux commented Feb 14, 2015

Are you sure Linux can handle that code?

On my linux/amd64 system, it also prints 2.

$ cat issue9862.go 
package main
var a [1 << 31]byte
func main() {
        println(a[0])
}
$ go version
go version devel +a809dc7 Sat Feb 14 01:01:19 2015 +0000 linux/amd64
$ go build issue9862.go
$ ./issue9862
2
$ size ./issue9862
   text    data     bss     dec     hex filename
 673232    2466  191856  867554   d3ce2 issue9862

In general, our toolchain can't handle static data (or text, for that matter)
bigger than 2GB.

@minux minux changed the title Large bss isn't initialized on darwin cmd/ld: handle >2GB static data Feb 14, 2015
@randall77
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You're right, on my linux/amd64 system at tip it prints 2. Turns out I was in the wrong directory and tested go 1.2.1. Go 1.2.1 generates the correctly sized bss, at least.

@minux
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minux commented Feb 14, 2015

I've experimented with various released version of Go:

$ go1 build a.go 
# command-line-arguments
./a.go:3: array bound must be non-negative
$ go112 build a.go 
$ size a
   text    data     bss     dec     hex filename
 264114   12368 2147557304      2147833786      800557ba        a
$ ./a
0
$ go121 build a.go
$ size a
   text    data     bss     dec     hex filename
 342097   18072 2147603800      2147963969      80075441        a
$ ./a
0
$ go133 build a.go
$ size a
   text    data     bss     dec     hex filename
 318996   16656  118920  454572   6efac a
$ ./a
2
$ go141 build a.go 
$ size a
   text    data     bss     dec     hex filename
 404626   12968  100392  517986   7e762 a
$ ./a
0

It's broken since Go 1.3.

@rsc rsc changed the title cmd/ld: handle >2GB static data cmd/ld: reject >2GB static data Apr 26, 2015
@josharian
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Possibly related: #7980

@rsc rsc changed the title cmd/ld: reject >2GB static data cmd/link: reject >2GB static data Jun 8, 2015
@gopherbot
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CL https://golang.org/cl/11715 mentions this issue.

@rsc rsc closed this as completed in 6f80e5e Jun 30, 2015
@golang golang locked and limited conversation to collaborators Jun 29, 2016
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@bradfitz @josharian @minux @randall77 @gopherbot