FCO uses a json configuration to resolve symbols.
For example {"AAAA":"BBBB"} means the pass should replace a call to function AAAA with a call to the result of void* handle=dlopen(NULL,FLAGS);dlsym(handle,"BBBB")
By default configuration is loaded from ~/Hikari/SymbolConfig.json

• -fcoconfig=PATH Override the path used to load SymbolConfig.json
• -fco_flag=VALUE Override the value of RTLD_GLOBAL|RTLD_NOW on your platform. If you are targeting Darwin/Android then the correct value is automatically applied

__DARWIN_ALIAS_C mess up symbols in LLVM IR.
For example open might has symbol name \0x01_open$UNIX2003.In which case corresponding json config would be {"\0x01_open$UNIX2003":"open"}
You should dump IR with -S -emit-llvm and build fcoconfig accordingly

You need to provide your own implementation of dlsym and dlopen by either statically embedding them in your code or linked as a separate library. Note that the return value of dlopen is not actually used outside of dlsym so you can pass any value as a placeholder.