size_t != int on any platform (on 64-bit its usually 64)
However think you are not using +2G sizes. However it might
break on negative values due to unsigned int64 -> int32 conversion.

.\mod_proxy_cluster.c(677) : warning C4267: '=' : conversion from 'size_t' to 'int', possible loss of data
.\mod_proxy_cluster.c(1026) : warning C4267: '=' : conversion from 'size_t' to 'int', possible loss of data
.\mod_proxy_cluster.c(1020) : warning C4101: 'name' : unreferenced local variable
.\mod_proxy_cluster.c(1092) : warning C4101: 'ret' : unreferenced local variable
.\mod_proxy_cluster.c(1225) : warning C4267: '=' : conversion from 'size_t' to 'int', possible loss of data
.\mod_proxy_cluster.c(1226) : warning C4267: '=' : conversion from 'size_t' to 'int', possible loss of data
.\mod_proxy_cluster.c(1910) : warning C4244: 'return' : conversion from '__int64' to 'int', possible loss of data
.\mod_proxy_cluster.c(2040) : warning C4267: 'function' : conversion from 'size_t' to 'int', possible loss of data