cmd/gc: wrong order of initialization when using method calls.

[axw]

Before filing a bug, please check whether it has been fixed since the
latest release. Search the issue tracker and check that you're running the
latest version of Go:

Run "go version" and compare against
http://golang.org/doc/devel/release.html  If a newer version of Go exists,
install it and retry what you did to reproduce the problem.

Thanks.

What steps will reproduce the problem?
If possible, include a link to a program on play.golang.org.
1. Clone math package in GOPATH, give it a different name (newmath).
2. Modify zipf.go to declare a package level variable X, type string, with an
initialiser (say "X").
3. Modify rng.go to declare another called Y which takes X and adds some string to it
(say "Y", to make "XY").
3. Modify rng.go to println(Y) at the top of rngSource.Seed.
4. Run a program that calls rand.Seed(0)

What is the expected output?

The string "XY" printed during initialisation, again when rand.Seed is called
from main.

What do you see instead?

An empty line (during init) followed by "XY" (rand.Seed called in main).

Which compiler are you using (5g, 6g, 8g, gccgo)?

8g

Which operating system are you using?

Ubuntu Linux 12.04 x86

Which version are you using?  (run 'go version')

go version weekly.2012-03-27 +d2213960ade2

Please provide any additional information below.

This all seems to stem from the initialisation of the globalRand variable in rand.go.
It appears that the compiler has missed the transitive dependency of globalRand on Y.

If you add a function, say "primethepump", to rng.go referencing Y, and call
it in
NewSource just prior to rng.Seed, then Y will be properly initialised.

I've attached the modified math package and calling program which exhibit the issue.
Sorry, I haven't been able to isolate the problem further so far.

Attachments:

1. varinit.tar.gz (159815 bytes)

[remyoudompheng]

Comment 1:

Please make your examples minimal: for example, all files in newmath and newmath/big,
newmath/cmplx, are totally irrelevant to your problem.
Here is a reproducer (prints "\nhelloworld\n"). If the method call is replaced by a Func
call (Func(0)), it prints "hello world\nhello world\n".
package main
import "fmt"
type T int
func (r T) Method() int { fmt.Println(s); return 0 }
func Func(r T) int      { fmt.Println(s); return 0 }
var (
      dummy = T(0).Method()
      s     = fmt.Sprint("hello world")
)
func main() { T(0).Method() }
Another facet of the bug is that the following incorrect program compiles (gccgo refuses
it).
package p
import "fmt"
type T int
func (r T) Method() int { fmt.Println(dummy); return 1 }
var dummy = T(0).Method()

[remyoudompheng]

Comment 2:

A hacky proposal.
http://golang.org/cl/6455055/

Status changed to Started.

[remyoudompheng]

Comment 3:

This issue was closed by revision 6cbf35c.

Status changed to Fixed.