Found the following significant warnings:
  epanet2.h:91:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.h:99:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.h:101:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.h:103:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.h:111:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.h:123:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.h:125:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.h:135:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.h:145:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.h:149:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.h:151:3: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.c:30:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.c:37:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.c:132:15: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.c:145:15: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.c:147:15: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.c:149:15: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.c:157:15: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.c:175:15: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.c:177:15: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.c:187:15: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.c:197:15: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.c:204:15: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  epanet2.c:206:15: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  filemanager.h:42:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  filemanager.c:40:16: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.h:23:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.h:39:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.h:41:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.h:43:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.h:48:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.h:50:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.h:51:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.h:52:1: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mempool.h:19:8: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mempool.c:42:25: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  mempool.c:68:18: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.c:354:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.c:937:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.c:969:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.c:988:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.c:1028:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.c:1059:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.c:1075:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
  toolkit.c:1091:6: warning: function declaration isn’t a prototype [-Wstrict-prototypes]
See ‘/home/hornik/tmp/R.check/r-devel-gcc/Work/PKGS/epanet2toolkit.Rcheck/00install.out’ for details.
* used C compiler: ‘gcc-12 (Debian 12.2.0-13) 12.2.0’