Found the following significant warnings:
  core/core/error.c:65:41: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  core/graph/attributes.c:290:41: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  core/random/random.c:546:33: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  vendor/plfit/gss.h:132:40: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  vendor/plfit/gss.c:60:40: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  vendor/plfit/platform.c:36:21: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  vendor/plfit/mt.c:20:34: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  rrandom.c:108:26: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  ./rrandom.h:26:26: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  ./init.c:51:31: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  ./init.c:104:29: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  rinterface.c:2506:24: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  rinterface.c:2522:34: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
  rinterface.c:9433:22: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
See ‘/data/gannet/ripley/R/packages/tests-clang/igraph.Rcheck/00install.out’ for details.