Many executable programs are originally generated from
more than one source file.
On MPE/iX, each source file is compiled separately to produce a
relocatable object module.
The linking phase of program development makes a relocatable
object file into an executable program file.
It can also bring together separately
compiled relocatable object modules into an executable program file.
Use the MPE/iX command :LINK to automatically access Link Editor to create an executable program file from one or more relocatable object modules.
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Link Editor on MPE/iX replaces Segmenter on MPE V/E. You can still use Segmenter in MPE/iX Compatibility Mode. For detailed information, refer to MPE Segmenter Reference Manual (30000-90011). For an explanation of the differences between Link Editor and Segmenter, refer to Link Editor/XL Reference Manual (32650-90030). :LINK is the MPE/iX counterpart to :PREP on MPE V/E systems. However, it operates differently and has different options. For an explanation of the differences between :LINK and :PREP, refer to Link Editor/XL Reference Manual (32650-90030). Figure 3-3 “Linking and Using User Libraries” shows the role of :LINK and Link Editor in MPE/iX.
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:LINK operates on one or more relocatable object modules created by a native compiler to perform the following tasks:
Search one or more relocatable libraries (RLs)
and resolve references to them in any of the relocatable object modules
being linked.
Resolve references among the relocatable object modules.
Merge all the relocatable object modules associated with one
program to create an executable program file.
If you use language commands that compile, link, and execute in one command (for example, :PASXLGO and :COB85XLG) or compile and link in one command (for example, :PASXLLK and :FTNXLLK), then linking is automatic. When you compile separately, you can use the MPE/iX command :LINK to produce an executable program file. Use this method when you want to use values different from standard Link Editor defaults. :LINK invokes Link Editor and passes the specified parameters to it. (An analogous LINK command exists in Link Editor; the MPE/iX command :LINK simply provides a short cut.)
Creating Executable Program Files |
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The MPE/iX command :LINK creates a load module (an
executable program file).
The :LINK command invokes Link Editor,
which is an MPE/iX subsystem that prepares compiled programs for
execution and maintains libraries.
When invoked by using :LINK, Link Editor resolves
external references in relocatable object modules by merging
relocatable object modules to produce an executable program file
containing all of the code and data that was in the relocatable
object modules.
It assigns final addresses to each symbol (for a variable
or procedure) to ensure that none overlap each other in the
executable program file.
These addresses are called virtual addresses, because they are
still subject to a final relocation when the program is loaded
into physical memory.
Once virtual addresses are determined, Link Editor can resolve
many of the references that could not be resolved at compile
time, because the symbol tables from all of the relocatable
object modules have been merged to one table.
You can specify the relocatable libraries to search for unresolved
references at link time. Any remaining external calls must be resolved at load time.
:LINK parameters can specify indirect files. An indirect file is a file list contained in an ASCII file. For example, in the :LINK command, an indirect file can be used to specify one of the following lists:
Relocatable libraries (RLs) to merge
Executable libraries (XLs) names to put in a program header
For an overview of Link Editor, refer to Chapter 4. For detailed information on :LINK and Link Editor, refer to Link Editor/XL Reference Manual (32650-90030).
You can request options at link time to:
Produce a program file map.
Search specified relocatable libraries (RLs) for any
required code not found in the relocatable object module.
Give the executable program file certain privileges and capabilities.
Symbol Listing |
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Example 3-1 shows a source file named EX1SRC.
An executable program file has been created for EX1SRC
named EX1PROG.
Example 3-1 Source File Example
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IDENTIFICATION DIVISION.
PROGRAM-ID. EX1
ENVIRONMENT DIVISION.
INPUT-OUTPUT DIVISION.
FILE-CONTROL.
SELECT IFILE ASSIGN "IFILE".
SELECT PFILE ASSIGN "PFILE".
DATA DIVISION.
FILE SECTION.
FD IFILE.
01 IREC.
05 NAME PIC X(30).
05 SOC-SEC PIC X(9).
05 HIRE-DATE.
10 MO PIC XX.
10 DA PIC XX.
10 YR PIC XX.
05 SALARY PIC S9(6).
05 PIC X(29).
FD PFILE.
01 PREC.
05 SOC-SEC PIC X(9).
05 PIC XX.
05 NAME PIC X(30).
05 PIC XX.
05 HIRE-DATE.
10 MO PIC XX.
10 PIC X.
10 DA PIC XX.
10 PIC X.
10 YR PIC XX.
05 PIC X(81).
01 HREC.
05 HSOC-SEC PIC X(11).
05 HNAME PIC X(32).
05 HHIRE-DATE PIC X(89).
WORKING STORAGE SECTION.
01 LNCNT PIC S9(4) BINARY VALUE 60.
01 W-DATE.
05 WYR PIC XX.
05 PIC X(4).
PROCEDURE DIVISION.
P1.
ACCEPT W-DATE FROM DATE.
OPEN INPUT IFILE OUTPUT PFILE.
PERFORM WITH TEST AFTER UNTIL SOC-SEC OF IREC = ALL "9"
READ IFILE
AT END MOVE ALL "9" TO SOC-SEC OF IREC
NOT AT END
IF WYR = YR OF IREC THEN
ADD 1 TO LNCNT
IF LNCNT > 50 PERFORM HEADINGS END-IF
MOVE SPACES TO PREC
MOVE CORR IREC TO PREC
WRITE PREC AFTER ADVANCING 1 LINE
END-IF
END-READ
END PERFORM
CLOSE IFILE PFILE
STOP RUN.
HEADINGS.
MOVE "SOC-SEC" TO HSOC-SEC.
MOVE "NAME" TO HNAME.
MOVE "HIRE DATE" TO HHIRE-DATE.
WRITE PREC AFTER ADVANCING PAGE.
MOVE 0 TO LNCNT.
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The commands
:LINKEDIT
LinkEd> LISTPROG EX1PROG
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invoke HP Link Editor/XL and create a program map displaying the symbols in EX1PROG, as shown in the following example:
PROGRAM : EX1PROG
XL LIST
CAPABILITIES : BA, IA
HEAP SIZE :
STACK SIZE :
VERSION : 85082112
Sym C H X P Sym Sym Sym Lset
Name Type Scope Value Name
---- - - - - ---- ----- ----- ----
$START 0 3 3 sec_p univ 000059B7
_start 0 3 3 sec_p univ 00005A07
ex1 0 3 3 pri_p univ 000059EB
M$1 0 data local dp+00000000
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In this program map, the portion preceding the symbol table is the header, which provides general information about the executable program file:
PROGRAM names the executable program file.
XL LIST shows the names of executable libraries specified in the XL parameter of the LINK command.
CAPABILITIES shows the capabilities assigned to the program in the CAP parameter of the LINK command.
HEAP SIZE shows the value specified in the
NMHEAP parameter of the LINK command.
STACK SIZE shows the value specified in the
NMSTACK parameter of the LINK command.
VERSION shows the executable program file format version.
The header information is followed by a list of symbols in the executable program file. For information on understanding the symbol listing, refer to Link Editor/XL Reference Manual (32650-90030).
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