[hurd, commited] hurd: clamp the setpriority prio argument to the range [-NZERO, NZERO-1]

From: Diego Nieto Cid <[email protected]>

The Open Group Base Specifications Issue 8
getpriority ( https://pubs.opengroup.org/onlinepubs/9799919799/ )

<< The nice value is in the range [0,2*{NZERO} -1], while the
   return value for getpriority() and the third parameter for
   setpriority() are in the range [-{NZERO},{NZERO} -1]. >>

So given that NZERO is defined to 20, we shall use it to clamp to the range
specified by POSIX.

That range is then mapped to something similar to [0, 2*{NZERO}-1], as
specified by POSIX, through the usage of the macro NICE_TO_MACH_PRIORITY
and MACH_PRIORITY_TO_NICE. (i.e. [5, 45] )
---
 sysdeps/mach/hurd/setpriority.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/sysdeps/mach/hurd/setpriority.c b/sysdeps/mach/hurd/setpriority.c
index 23d678bf40..8107098991 100644
--- a/sysdeps/mach/hurd/setpriority.c
+++ b/sysdeps/mach/hurd/setpriority.c
@@ -28,7 +28,7 @@ __setpriority (enum __priority_which which, id_t who, int prio)
   error_t pidloser, priloser;
   unsigned int npids, ntasks, nwin, nperm, nacces;
 
-  prio = MAX (0, MIN (2 * NZERO - 1, prio));
+  prio = MAX ((-NZERO), MIN ((NZERO - 1), prio));
 
   error_t setonepriority (pid_t pid, struct procinfo *pi)
     {
-- 
2.53.0