runtime: fix gogetenv on Plan 9

LGTM=rsc
R=rsc, ality
CC=golang-codereviews
https://golang.org/cl/137030043

diff --git a/src/pkg/runtime/env_plan9.go b/src/pkg/runtime/env_plan9.go
index 85c1c856b0f98f830783dc306ff09fede2951256..b6dcb4c1eaa09ee4a1e85cbd5fc0472eb070f31e 100644 (file)
--- a/src/pkg/runtime/env_plan9.go
+++ b/src/pkg/runtime/env_plan9.go
@@ -30,21 +30,11 @@ func gogetenv(key string) string {
        if fd < 0 {
                return ""
        }
-       n := seek(fd, 0, 2)
-
-       var p unsafe.Pointer
-
-       // Be sure not to allocate for $GOTRACEBACK.
-       if key == "GOTRACEBACK" {
-               if n >= 128 {
-                       return ""
-               }
-               p = unsafe.Pointer(&tracebackbuf[0])
-       } else {
-               p = gomallocgc(uintptr(n+1), nil, 0)
-       }
+       n := seek(fd, 0, 2) - 1
+
+       p := make([]byte, n)
 
-       r := pread(fd, p, int32(n), 0)
+       r := pread(fd, unsafe.Pointer(&p[0]), int32(n), 0)
        close(fd)
        if r < 0 {
                return ""
@@ -52,7 +42,7 @@ func gogetenv(key string) string {
 
        var s string
        sp := (*_string)(unsafe.Pointer(&s))
-       sp.str = (*byte)(p)
+       sp.str = &p[0]
        sp.len = int(r)
        return s
 }