An object code generating system includes: a storage unit configured to store a first source file; and an object code generating section. The object code generating section is configured to read the first source file, generate function data indicating an arrangement address and size of each of the functions in the first source file, generate an execution format file for the first source file; and read a second source file obtained by modifying at least one of the functions as a specific function in the first source file, and the function data from the storage unit, generate a dummy function corresponding to the modified specific function when the modified specific function is discovered in the second source file, arrange the dummy function at an arrangement address different from the arrangement addresses of the functions, and arrange a branch command to the dummy function at the different arrangement address.