Found the following significant warnings:
  GPS_v3.2.c:60:4: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:10: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:14: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:21: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:27: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:38: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:40: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:42: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:44: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:46: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:48: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:50: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:58: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:60:60: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:4: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:6: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:10: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:17: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:22: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:24: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:42: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:44: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:48: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:50: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:52: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:54: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:56: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:61:66: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:154:4: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:158:30: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:158:33: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:158:39: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:173:8: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:173:11: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:173:16: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:173:20: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:204:27: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:204:35: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:204:38: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:222:7: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:222:11: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:227:7: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:227:10: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:231:9: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:231:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:235:9: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:235:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:244:46: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:244:50: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:248:8: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:248:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:334:16: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:334:19: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:334:26: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:334:30: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:338:9: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:338:18: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:338:21: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:348:21: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:348:25: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:364:7: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:364:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:368:5: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:368:14: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:368:18: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:375:5: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:375:14: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:375:18: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:378:5: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:378:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:386:9: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:386:13: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:386:20: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:4: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:10: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:14: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:21: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:27: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:38: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:40: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:42: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:44: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:46: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:48: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:50: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:58: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:420:60: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:4: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:6: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:10: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:17: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:22: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:24: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:42: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:44: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:48: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:50: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:52: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:54: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:56: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:421:66: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:526:4: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:530:31: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:530:34: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:530:40: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:544:9: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:544:14: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:544:22: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:544:28: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:544:30: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:544:32: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:544:34: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:544:36: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:544:42: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:544:44: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:582:7: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:582:11: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:588:7: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:588:10: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:592:9: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:592:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:596:9: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:596:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:605:8: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:605:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:626:46: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:626:50: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:696:16: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:696:19: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:696:26: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:696:30: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:699:9: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:699:18: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:699:21: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:719:21: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:719:25: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:753:7: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:753:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:757:5: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:757:14: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:757:18: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:764:5: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:764:14: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:764:18: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:767:5: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:767:12: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:775:9: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:775:13: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:775:20: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:920:23: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:920:27: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:922:4: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:947:9: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:947:13: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:951:7: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:951:11: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1019:23: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1019:27: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1021:4: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1046:7: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1046:11: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1097:23: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1097:27: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1099:4: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1153:16: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1153:20: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1157:7: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1157:11: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1201:14: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1201:22: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1201:24: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1201:28: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1201:38: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1218:23: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1218:27: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1220:4: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1290:5: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1290:8: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1290:14: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1290:23: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1290:25: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1301:7: warning: invalid UTF-8 in comment [-Winvalid-utf8]
  GPS_v3.2.c:1301:11: warning: invalid UTF-8 in comment [-Winvalid-utf8]
See '/home/hornik/tmp/R.check/r-devel-clang/Work/PKGS/msgps.Rcheck/00install.out' for details.