strange warning when build program

[PVC Pirates]

I have created a pair of files: user_common.c and user_common.h and added them to the workspace. user_common.h includes user_common.c . Inside user_common.c are several functions I use during an interrupt to read a sensor. all functions in user_common.c are stated in user_common.h with the return type and any parameters in () then followed by a semicolon. In each file where any function from user_common.c is used, user_common.h is included. When I make or build everything, the build succeeds but for each function i used that came from user_common.c, I receive the following error:
" file path : line number : Warning [2058] call of function without prototype ". I have no idea what it means, but the functions don't work. Could this error be a side effect of the problem that is preventing the functions from working correctly? Any help would be appreciated.