Found the following significant warnings:
  data.table.h:112:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  data.table.h:125:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  data.table.h:132:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  data.table.h:188:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  data.table.h:191:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  data.table.h:193:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  assign.c:1140:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  assign.c:1181:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  forder.c:71:13: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  forder.c:78:13: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  forder.c:113:13: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  forder.c:376:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  forder.c:381:5: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fread.c:78:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fread.c:1278:38: warning: the comparison will always evaluate as ‘false’ for the pointer operand in ‘nastr + 8’ must not be NULL [-Waddress]
  fwrite.h:14:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:15:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:16:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:17:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:18:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:19:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:20:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:21:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:22:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:23:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:24:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:25:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:26:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:27:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  fwrite.h:28:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:44:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:45:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:46:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:47:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:48:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:49:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:50:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:51:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:52:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:53:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:54:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:55:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:56:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:57:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:58:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:59:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:60:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:61:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:62:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:63:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:64:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:65:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:66:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:67:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:68:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:69:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:70:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:71:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:72:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:73:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:74:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:75:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:76:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:77:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:78:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:79:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:80:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:81:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:82:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:83:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:84:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:85:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:86:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:87:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:88:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:89:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:90:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:91:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:92:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:93:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:94:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:95:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:96:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:97:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:98:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:99:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:100:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:101:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:102:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:103:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:104:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:105:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:106:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:107:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:108:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:109:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:110:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:111:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:112:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:113:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:114:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:115:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:116:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:117:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:118:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:119:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:120:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:121:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:122:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:123:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:124:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:125:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:126:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:127:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:130:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:231:13: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:387:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:394:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  init.c:415:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  openmp-utils.c:32:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  openmp-utils.c:171:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  openmp-utils.c:176:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  openmp-utils.c:180:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  snprintf.c:187:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  utils.c:380:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
See ‘/home/hornik/tmp/R.check/r-devel-gcc/Work/PKGS/data.table.Rcheck/00install.out’ for details.