go.sys/unix: use syscall.Errno for errors

If we use a local type, it won't compare properly with errors from
the rest of the standard library. Errors are the one type from syscall
that propagates through the system, so it's important to have only
one type for them.

Ditto for syscall.Signal.

LGTM=dave
R=rsc, dave
CC=golang-codereviews
https://golang.org/cl/123490043

unix/exec_solaris.go

@@ -5,6 +5,7 @@
 package unix
 
 import (
+	"syscall"
 	"unsafe"
 )
 
@@ -21,20 +22,20 @@ type SysProcAttr struct {
 func runtime_BeforeFork()
 func runtime_AfterFork()
 
-func chdir(path uintptr) (err Errno)
-func chroot1(path uintptr) (err Errno)
-func close(fd uintptr) (err Errno)
-func execve(path uintptr, argv uintptr, envp uintptr) (err Errno)
+func chdir(path uintptr) (err syscall.Errno)
+func chroot1(path uintptr) (err syscall.Errno)
+func close(fd uintptr) (err syscall.Errno)
+func execve(path uintptr, argv uintptr, envp uintptr) (err syscall.Errno)
 func exit(code uintptr)
-func fcntl1(fd uintptr, cmd uintptr, arg uintptr) (val uintptr, err Errno)
-func forkx(flags uintptr) (pid uintptr, err Errno)
-func ioctl(fd uintptr, req uintptr, arg uintptr) (err Errno)
-func setgid(gid uintptr) (err Errno)
-func setgroups1(ngid uintptr, gid uintptr) (err Errno)
-func setsid() (pid uintptr, err Errno)
-func setuid(uid uintptr) (err Errno)
-func setpgid(pid uintptr, pgid uintptr) (err Errno)
-func write1(fd uintptr, buf uintptr, nbyte uintptr) (n uintptr, err Errno)
+func fcntl1(fd uintptr, cmd uintptr, arg uintptr) (val uintptr, err syscall.Errno)
+func forkx(flags uintptr) (pid uintptr, err syscall.Errno)
+func ioctl(fd uintptr, req uintptr, arg uintptr) (err syscall.Errno)
+func setgid(gid uintptr) (err syscall.Errno)
+func setgroups1(ngid uintptr, gid uintptr) (err syscall.Errno)
+func setsid() (pid uintptr, err syscall.Errno)
+func setuid(uid uintptr) (err syscall.Errno)
+func setpgid(pid uintptr, pgid uintptr) (err syscall.Errno)
+func write1(fd uintptr, buf uintptr, nbyte uintptr) (n uintptr, err syscall.Errno)
 
 // Fork, dup fd onto 0..len(fd), and exec(argv0, argvv, envv) in child.
 // If a dup or exec fails, write the errno error to pipe.
@@ -48,12 +49,12 @@ func write1(fd uintptr, buf uintptr, nbyte uintptr) (n uintptr, err Errno)
 // because we need to avoid lazy-loading the functions (might malloc,
 // split the stack, or acquire mutexes). We can't call RawSyscall
 // because it's not safe even for BSD-subsystem calls.
-func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr *ProcAttr, sys *SysProcAttr, pipe int) (pid int, err Errno) {
+func forkAndExecInChild(argv0 *byte, argv, envv []*byte, chroot, dir *byte, attr *ProcAttr, sys *SysProcAttr, pipe int) (pid int, err syscall.Errno) {
 	// Declare all variables at top in case any
 	// declarations require heap allocation (e.g., err1).
 	var (
 		r1     uintptr
-		err1   Errno
+		err1   syscall.Errno
 		nextfd int
 		i      int
 	)