System and methods for linking compiled code with extended dictionary support

• US 5,408,665 A
• Filed: 04/30/1993
• Issued: 04/18/1995
• Est. Priority Date: 04/30/1993
• Status: Expired due to Term

• Current Assignee: CodeGear (Idera, Inc.)
• Original Assignee: Borland International, Inc. (Open Text Corporation)
• Inventors: Fitzgerald, Judith A.
• Primary Examiner(s): Heckler, Thomas M.
• Application Number:
  US08/056,686
• Time in Patent Office: 718 Days
• Field of Search: 395/700, 364/DIG. 1
• US Class Current: 717/163
• CPC Class Codes: G06F 8/433 Dependency analysis; Data or control flow analysis

Abstract

A development system of the present invention includes a compiler, a linker, and an interface. The compiler serves to compile source listings into object modules (which are initially stored in .OBJ files). A librarian is provided for combining desired ones of the .OBJ files into one or more library files. For each library file, the librarian provides an Extended Dictionary of the present invention, which includes a Dependency List and an Unresolved Externals List for each module of the library. Methods are described for linking object modules from .OBJ files and library files, where library object modules which are not needed for the link may be determined before the libraries are scanned during the first pass of the linker. In this manner, library object modules which are not needed during subsequent linking operations can be skipped.

Claims

1. In a computer system which creates executable programs from a plurality of compiled object modules, said plurality of object modules having at least one public and external reference and selected ones of the object modules of which are stored in at least one library file, an improved method for linking the object modules into an executable program, the improvement comprising:

(a) providing each library file with a Standard Dictionary, said Standard Dictionary being a portion of each library file having entries which lists all public references from the object modules stored in the library file where a public reference is capable of satisfying an external reference in another object module;

(b) providing each library file with an Extended Dictionary, said Extended Dictionary being a portion of each library file which has a dependent modules list for each object module in the library file;

(c) for each public reference entry in the Standard Dictionary which is not an object module name, storing a reference to a name of an object module which includes the public reference;

(d) for each public reference entry in the Standard Dictionary which is an object module name, storing a reference to the dependent object modules list in the Extended Dictionary for the named object module;

(e) for each external reference in a non-library object module which is not satisfied by another non-library object module during linking, said computer system locating a public reference in said at least one library file which satisfies the external reference; and

(f) said computer system determining from said Standard Dictionary and said Extended Dictionary which object modules from the library file are necessary for linking.

2. The method of claim 1, further comprising:

(g) for each object module in a library file, storing in the Extended Dictionary a list of references for the object module which are unresolved by the library file; and

(h) for each public reference entry in the Standard Dictionary which is an object module name, storing a reference to the list of unresolved references for the named object module, whereby steps (e)-(f) are performed for any references from the list of unresolved references which has not been resolved.

3. The method of claim 1, wherein each Standard Dictionary entry includes a name and a file offset for the public reference.

4. The method of claim 1, wherein said reference to a name of an object module stored in Standard Dictionary entry includes a pointer back into the Standard Dictionary.

5. The method of claim 1, wherein each entry of the dependent object modules list references an entry of the Standard Dictionary which specifies the name of a dependent object module.

6. A computer system for creating an improved library file for storing compiled object modules having references, a reference being public if it is accessible by other object modules and a reference being external if it refers to a public reference in another object module, said system comprising:

(a) means for storing in the library file a list of all public references in the object modules stored in the library file; and

(b) means for storing in the library file for each of the object modules a list of object modules which depend from said each object module and a list of all references for the object module which are external to the library file, said lists for selecting object modules from the library file which are necessary for linking, an object module being necessary if it contains a reference needed during linking.

7. The system of claim 6, further comprising:

(c) linker means for linking together selected ones of the object modules for constructing a program executable by a microprocessor, said means including means for determining from said lists said selected ones of the object modules stored in the library file to link.

8. The system of claim 6, wherein said list of all public references comprises a plurality of entries, each entry storing a name of a public reference followed by a pointer.

9. The system of claim 8, wherein, if said name of the public reference is not a name of an object module, said pointer points to an entry in the list for an object module which defines the public reference.

10. The system of claim 8, wherein, if said name of the public reference is a name of an object module, said pointer references an index to said list of object modules which depend from the object module and to said list of references for the object module which are external to the library file.

11. A development computer system for generating a computer program for instructing operation of a processor, the system comprising:

compiler means for creating from source listings object modules having instructions for directing operation of the processor, said object modules including at least one object module which is dependent upon instructions of another object module;

librarian means for storing a plurality of object modules together as a single library file, said librarian means including dictionary means for storing for each object module a first list specifying other object modules stored in the library file which said each object module is dependent upon and for storing for said each object module a second list specifying other object modules not stored in the library file which said each object module is dependent upon; and

linker means for linking at least one object module with at least one library file for generating the computer program, said at least one object module being dependent upon at least one other object module stored in said at least one library file, said linker means including means, responsive to said dictionary means, for determining for said at least one object module all object modules stored in the library file which are necessary for generating the computer program.

12. The system of claim 11, wherein said librarian means includes means for storing a table having an entry for each reference within a library file which is public (global) to the library file.

13. The system of claim 12, wherein said table has a format which is compatible with Microsoft standard MS-DOS library format.

14. The system of claim 12, wherein each entry of said table includes a name of a public reference.

15. The system of claim 14, wherein said each entry further includes a pointer.

16. The system of claim 15, wherein a pointer for a public reference which is not an object module stores a reference to another entry of said table, the entry specifying an object module of the library file where said public reference is defined.

17. The system of claim 15, wherein a pointer for a public reference which is an object module stores a reference to said first and second lists for the object module.

18. The system of claim 17, wherein said reference to said first and second lists includes an index into a table storing first and second pointers, said first pointer referencing the first list for the object module, said second pointer referencing the second list for the object module.

19. The system of claim 15, wherein each name includes at least one byte value specifying a length of the name followed by at least one byte value specifying alphanumeric characters for the name, and wherein each pointer includes at least two byte values specifying another location in the library file.

20. The system of claim 12, wherein said first list includes entries specifying other object modules stored in the library file which said each object module is dependent upon, each of the entries storing a pointer specifying an entry in said table for one of said other object modules.

21. The system of claim 12, wherein said second list includes entries specifying other object modules not stored in the library file which said each object module is dependent upon, each of the entries storing a pointer to a character string specifying a name of one of said other object modules.

22. The system of claim 11, wherein each object module is stored in the system in a format compatible with Intel Object Module Format (OMF) standard.

23. In a computer system, a method for linking together a plurality of code modules storing processor instructions for generating a computer program, selected ones of the code modules being stored collectively within at least one library file, the method comprising:

(a) storing for each code module of each said at least one library file a first list specifying interdependencies between said each code module and other code modules stored within its library file;

(b) storing for each code module of each said library file a second list specifying interdependencies between said each code module and other code modules not stored within its library file;

(c) storing a third list in each said at least one library file, said third list specifying each code module stored in the library file and pointers to said first and second lists for said specified each code module;

(d) receiving an input specifying at least one object module to be linked with at least one library file for generating a computer program;

(e) for said at least one object module to be linked, determining from said first, second, and third lists which code modules stored within said at least one library file are required for linking; and

(f) linking said at least one object module to be linked with said required code modules stored within said at least one library file for generating the computer program.

24. The method of claim 23, wherein step (e) includes:

for said at least one object module to be linked, locating which library file includes an object module required for linking by reading the third list of each said library file; and

determining any other object modules required for linking by reading the first and second lists of each required object module located in a library file.

25. The method of claim 23, wherein step (f) includes reading only said required code modules from said at least one library file, whereby code modules stored within said at least one library file which are not needed for linking are not read.

26. A system for generating a program for operating a computer, the system comprising:

means for compiling source code files into at least one compiled code module;

means, receiving input from said compiling means, for storing selected ones of said at least one compiled code module in at least one library file, and including means for storing with each said at least one library file for each said at least one compiled code module a dependency list and an unresolved list, said dependency list specifying interdependent compiled code modules which are present within a same library file and said unresolved list specifying interdependent compiled code modules which are not present within the same library file;

input means for receiving a list of at least one compiled code module for linking with at least one library file;

means, receiving input from said compiling means, said storing means and said input means, for determining which compiled code modules of said at least one library file are necessary for linking; and

means, receiving input from said compiling means, said storing means and said determining means, for generating the program by linking said at least one compiled code module of the list with said compiled code modules which are determined necessary for linking, whereby compiled code modules which are stored in said at least one library file and which are not necessary for linking are not processed by the system.

27. The system of claim 26, wherein each compiled code module comprises a plurality of records stored in a format compatible with Object Module Format (OMF) standard.

28. The system of claim 26, wherein the generating means includes means for scanning all said at least one library file for reading only compiled code modules which are necessary for linking.

29. The system of claim 26, wherein said determining means includes means for recursively processing said dependency and unresolved lists for each compiled code module called by a compiled code module of said list, whereby all compiled code modules called are processed by the generating means.

30. The system of claim 26, wherein each unresolved list stores names for symbols referenced by a compiled code module which are not resolved with a same library file, the names including names of other compiled code modules.