System for dynamically changing an execution program and method for doing the same

A computer system for compiling and linking source programs to generate load modules, and loading the load modules into a memory to be executed, comprising:

• additional link means for updating some of subroutines in the source programs, compiling the subroutines into object modules of new-version subroutines, determining external reference information of the object modules based on address information of the load modules, and creating an additional load module;
• additional load means for dynamically loading the additional load module in the memory space when load modules including old-version subroutines are loaded into the memory;
• transfer control means for transferring control to the new-version subroutines when the load modules call the old-version subroutines;
• and
• control return means for returning the control to a calling point when processing of the new-version subroutines is completed.

A method for changing execution programs in a computer system having a memory device for storing source programs and various modules which are created, a memory space into which said modules are loaded, and a CPU (central processing unit), for compiling the source programs into object modules, linking the object modules to generate load modules, resolving unresolved external reference information caused in the object modules, and loading the load modules into the memory space, said method comprising the steps of:

• a) resolving unresolved external reference information caused in an object module including a second subroutine based on the external reference information resolved when the load modules are generated, and creating an additional load module from the object module including the second subroutine, thereby updating a first subroutine loaded into said memory space;
• b) loading the additional load module created in said step a) into said memory space;
• c) calling the second subroutine of the additional load module in place of the first subroutine when the first subroutine is called from the load modules;
• and
• d) returning control to points where the first subroutine is called when processing of the second subroutine is completed, and continuing the processing after the points.

A method of dynamically changing execution programs in a computer system for compiling and linking source programs to generate load modules, and loading the load modules into a memory to be executed, said method comprising the steps of:

• a) updating some of subroutines in the source programs, compiling the subroutines into object modules of new-version subroutines, determining external reference information of the object modules based on address information of the load modules, and creating an additional load module;
• b) dynamically loading the additional load module in the memory space when load modules including old-version subroutines are loaded into the memory;
• c) transferring control to the new-version subroutines when the load modules call the old-version subroutines;
• and
• d) returning the control to a calling point when processing of the new-version subroutines is completed.