psem: in sem_open, regard 0 /and/ -1 as failure; and then print the errno

VxWorks and RTEMS-4.9 return -1 on error, while Linux returns SEM_FAILED
which is NULL.

MultiCAN/src/tool/src/psem.c

@@ -394,11 +394,15 @@ int psem_named_create(char *name, int initial_state)
     sem=  (sem_open(name, O_CREAT | O_EXCL, 0,
                     initial_state ? 0 : 1));
 
-    if (-1==(long)sem)
+    if ((sem_t*)(-1)==sem || (sem_t*)(0)==sem)
       { if (errno==EEXIST)
           /* if the semaphore already existed, 1 is returned */
           return(1);
-        return(-1);
+        else
+          {
+            printf("psem_named_create: sem_open failed: %s\n", strerror(errno));
+            return(-1);
+          }
       };
     if (0!=sem_close(sem))
       return(-1);
@@ -429,9 +433,15 @@ boolean psem_named_open(char *name, psem_named *sem)
     *sem= (psem_named)mq;
     return(TRUE);
 #else
-    if (-1==((ptrdiff_t)(*sem= (sem_open(name, 0, 0, 0)))))
-      return(FALSE);
-    return(TRUE);
+    *sem= (sem_open(name, 0, 0, 0));
+
+    if ((sem_t*)(-1)==*sem || (sem_t*)(0)==*sem)
+      {
+        printf("psem_named_create: sem_open failed: %s\n", strerror(errno));
+        return FALSE;
+      }
+    else
+        return TRUE;
 #endif
   }