Sometimes it works, sometimes it fails.

% uname -a
Darwin xikinbook.local 12.4.0 Darwin Kernel Version 12.4.0: Wed May  1 17:57:12 PDT
2013; root:xnu-2050.24.15~1/RELEASE_X86_64 x86_64
% go version
go version devel +0d127e5a7d36 Fri Aug 16 16:02:55 2013 +0400 darwin/amd64
% gofmt -s -w .
runtime: goroutine stack exceeds 1000000000-byte limit
fatal error: stack overflow

goroutine 1 [stack split]:
runtime/race.FuncExit(0x710008)
    /Users/f/lib/go/src/pkg/runtime/race/race.go:73 fp=0x7000e0
runtime.racefuncexit()
    /Users/f/lib/go/src/pkg/runtime/race.c:137 +0x2d fp=0x7000f0
go/printer.(*printer).exprList(0xc21003f140, 0x0, 0xc21002da80, 0x1, 0x1, ...)
    /Users/f/lib/go/src/pkg/go/printer/nodes.go:260 +0x62 fp=0x700378
go/printer.(*printer).spec(0xc21003f140, 0x588850, 0xc21001ec30, 0x1, 0x700501)
    /Users/f/lib/go/src/pkg/go/printer/nodes.go:1345 +0x950 fp=0x7004c8
go/printer.(*printer).genDecl(0xc21003f140, 0xc21000ae40)
    /Users/f/lib/go/src/pkg/go/printer/nodes.go:1402 +0xc50 fp=0x700650
go/printer.(*printer).decl(0xc21003f140, 0x5884d0, 0xc21000ae40)
    /Users/f/lib/go/src/pkg/go/printer/nodes.go:1530 +0x127 fp=0x7006e8
go/printer.(*printer).declList(0xc21003f140, 0xc21003b500, 0x6, 0x8)
    /Users/f/lib/go/src/pkg/go/printer/nodes.go:1573 +0x1f3 fp=0x700758
go/printer.(*printer).file(0xc21003f140, 0xc21003b600)
    /Users/f/lib/go/src/pkg/go/printer/nodes.go:1581 +0x261 fp=0x700800
go/printer.(*printer).printNode(0xc21003f140, 0x1a18c0, 0xc21003b600, 0x0, 0x0)
    /Users/f/lib/go/src/pkg/go/printer/printer.go:1026 +0xa1c fp=0x700958
go/printer.(*Config).fprint(0x700ab0, 0x588da0, 0xc210031230, 0xc21000a2c0, 0x1a18c0,
...)
    /Users/f/lib/go/src/pkg/go/printer/printer.go:1165 +0xff fp=0x7009f8
go/printer.(*Config).Fprint(0x700ab0, 0x588da0, 0xc210031230, 0xc21000a2c0, 0x1a18c0,
...)
    /Users/f/lib/go/src/pkg/go/printer/printer.go:1223 +0xa4 fp=0x700a48
main.processFile(0xc21002d4b0, 0xa, 0x0, 0x0, 0x588448, ...)
    /Users/f/lib/go/src/cmd/gofmt/gofmt.go:121 +0x497 fp=0x700bf0
main.visitFile(0xc21002d4b0, 0xa, 0x5883c0, 0xc21001e1e0, 0x0, ...)
    /Users/f/lib/go/src/cmd/gofmt/gofmt.go:160 +0xee fp=0x700c48
path/filepath.walk(0xc21002d4b0, 0xa, 0x5883c0, 0xc21001e1e0, 0x234448, ...)
    /Users/f/lib/go/src/pkg/path/filepath/path.go:341 +0xad fp=0x700d18
path/filepath.walk(0x7fff5fbff214, 0x1, 0x5883c0, 0xc21001e190, 0x234448, ...)
    /Users/f/lib/go/src/pkg/path/filepath/path.go:359 +0x444 fp=0x700de8
path/filepath.Walk(0x7fff5fbff214, 0x1, 0x234448, 0x0, 0x0)
    /Users/f/lib/go/src/pkg/path/filepath/path.go:380 +0xdc fp=0x700e30
main.walkDir(0x7fff5fbff214, 0x1)
    /Users/f/lib/go/src/cmd/gofmt/gofmt.go:169 +0x49 fp=0x700e60
main.gofmtMain()
    /Users/f/lib/go/src/cmd/gofmt/gofmt.go:218 +0x85f fp=0x700f38
main.main()
    /Users/f/lib/go/src/cmd/gofmt/gofmt.go:176 +0x2c fp=0x700f48
runtime.main()
    /Users/f/lib/go/src/pkg/runtime/proc.c:209 +0x11f fp=0x700fa0
runtime.goexit()
    /Users/f/lib/go/src/pkg/runtime/proc.c:1373 fp=0x700fa8

goroutine 3 [syscall]:
runtime.goexit()
    /Users/f/lib/go/src/pkg/runtime/proc.c:1373