Found the following significant warnings:
  scrm/forest.cc:31:30: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:105:80: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:110:100: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:148:66: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:168:63: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:169:34: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:286:59: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:295:36: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:301:31: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:307:29: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:312:60: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:315:51: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:319:37: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:328:71: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:423:98: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:426:64: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:436:74: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:438:69: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:445:68: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:446:64: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:448:64: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:453:48: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:463:71: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:495:94: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:517:54: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:535:48: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:762:51: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:765:65: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:766:55: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:767:56: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:845:72: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:862:34: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:888:53: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:951:85: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:971:62: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:994:59: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:995:46: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1044:31: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1065:63: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1071:64: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1078:59: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1097:31: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1104:46: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1120:41: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1169:94: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1184:97: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1202:94: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1277:41: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1279:32: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1294:61: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1309:61: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1313:57: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1332:84: warning: statement has no effect [-Wunused-value]
  scrm/forest.cc:1339:72: warning: statement has no effect [-Wunused-value]
  scrm/node.cc:66:46: warning: statement has no effect [-Wunused-value]
  scrm/node.cc:68:46: warning: statement has no effect [-Wunused-value]
  scrm/node_container.cc:268:66: warning: statement has no effect [-Wunused-value]
  scrm/node_container.cc:275:61: warning: statement has no effect [-Wunused-value]
  scrm/node_container.cc:279:64: warning: statement has no effect [-Wunused-value]
  scrm/node_container.cc:285:61: warning: statement has no effect [-Wunused-value]
  scrm/param.cc:65:45: warning: statement has no effect [-Wunused-value]
See 'd:/Rcompile/CRANpkg/local/4.0/scrm.Rcheck/00install.out' for details.