Using the Features of PWB to Build a Program with Overlays

ID Number: Q60050

1.00 1.10 | 1.00 1.10

MS-DOS | OS/2

Summary:

A MAKE file built with PWB can be modified (within reason) with the

user supplied information section. This section, coded as

# << User_supplied_information >>

can contain other instructions that PWB (actually NMAKE or NMK) is

supposed to carry out during the MAKE cycle. All instructions that

follow this "fence" are not changed by PWB.

The following instructions detail two implementations of this "fence"

to allow PWB to build a program that uses overlays.

More Information:

While the following steps appear tedious, they are simple in practice.

Once the changes are made, the only time you need to edit the MAKE

file directly is to change your overlay structure, or to add or delete

modules. When adding or deleting modules, you must both edit the

program list (by choosing Edit Program List from the Make menu) and

modify the commands in the user section. If you are only modifying the

overlay structure, you change just the user section.

The overlay structure in the example is as follows:

HELLO.OBJ (root)

|

+----A.OBJ (first overlay)

|

+----B.OBJ (second overlay)

All of the .OBJs are built from .C files with the same base name.

1. Use PWB to build the program list in the normal way. This step is

the same for any new program list.

a. Start PWB.

b. Choose Set Program List from the Make menu, and specify a new

name -- HELLO.MAK in this example.

c. Add HELLO.C, A.C, and B.C to the list. (If you have additional

.C or .OBJ files, you would add them as well.) When all the

files are listed, select Set Dependencies.

d. Choose Build Options from the Options menu, click the Set

Initial Build Options button, and select DOS EXE.

e. From the Options menu, choose Compile Options, and select the

proper memory model.

f. From Options menu, choose Link Options, then choose Set Debug

Options, and turn off Incremental Link.

g. From the Options menu, choose Browse Options, and turn Generate

Browse Information on.

h. Choose Rebuild All from the Make menu to make sure that the

program builds properly without overlays. If it doesn't, review

your work in previous steps.

2. Now that you have a working program list, add the non-PWB

information to the end.

a. Choose Clear Program List from the Make menu so that you can

edit the MAKE file. Attempting to edit the current program list

results in the message "No-edit file may not be modified."

b. Choose Open from the File menu to open the MAKE file so you can

modify it.

c. Go to the end of the file and start a blank line. Starting in

column 1, add the following line:

# << User_supplied_information >>

Be sure to enter the line exactly as shown -- spacing is

significant. This line is a "fence". Everything below the fence

is yours and is not modified by PWB. Conversely, you should not

modify anything above the fence because that section belongs to

PWB.

d. Below the fence starting in column one, add the pseudo-target:

OVERLAID : $(OBJS)

Be sure it starts column 1. Do not put a blank line after this

line.

e. Copy the command section from the $(PROJ).EXE description block

to immediately follow the pseudo-target. The command section

begins on the line following the line that reads

$(PROJ).exe : $(OBJS)

and ends at the next blank line. Do not copy the $(PROJ).EXE

line, and do not leave a blank after the target. After you have

copied the commands, your file should appear as follows:

... PWB section here, unmodified ...

# << User_supplied_information >>

OVERLAID : $(OBJS)

!IF $(DEBUG) # copy of commands...

$(LRF) @<<$(PROJ).lrf

$(RT_OBJS: = +^

) $(OBJS: = +^

)

$@

...

f. Use the following procedure to modify the commands to link an

overlaid .EXE instead of a normal .EXE.

Note: There are two subsections in this section: a debug section

that starts at the first "!IF $(DEBUG)" and ends at "!ELSE", and

a release section that starts after the "!ELSE" and ends at the

first "!ENDIF".

You need to make the following modifications to both

subsections.

i. Delete the line that reads as follows:

) $(OBJS: = +^

After the right parenthesis on the line that moved up, put

your list of .OBJ files with parentheses to indicate which

ones go in which overlays. If you need to use more than one

line for all of your objects, be sure to put a plus sign (+)

at the end of each line except the last.

ii. Replace "$@" on the next line with "$(PROJ).EXE".

In our example,

$(LRF) @<<$(PROJ).lrf

$(RT_OBJS: = +^

) $(OBJS: = +^ # delete this line

) # append OBJ list here ...

$@ # replace this line with $(PROJ).EXE

becomes:

$(LRF) @<<$(PROJ).lrf

$(RT_OBJS: = +^

) hello.obj +

(a.obj) +

(b.obj)

$(PROJ).exe

Remember to make the changes in both branches of the !IF

$(DEBUG).

g. The last step is to modify the browser database build commands.

These are the two lines at the very end of the file that begin

with "$(NMAKEBSC...". PWB adds and deletes these lines in the

PWB section as you turn browser information on and off.

Since PWB won't delete and add these lines in the user section,

enclose them in !IF $(BROWSE)...!ENDIF so they'll be run only

when you ask for browse information. You also need to delete the

"$(NMFLAGS)" macro from the second line to prevent infinite

NMAKE recursion.

The following lines

$(NMAKEBSC1) MAKEFLAGS=

$(NMAKEBSC2) $(NMFLAGS) -f $(PROJFILE) $(PROJ).bsc

become:

!IF $(BROWSE)

$(NMAKEBSC1) MAKEFLAGS=

$(NMAKEBSC2) -f $(PROJFILE) $(PROJ).bsc

!ENDIF

If you need special NMAKE options for building the browser

database, just add them where you removed $(NMFLAGS).

3. Reactivate the MAKE file by choosing Set Program List from the

Make menu.

4. With these changes, if you choose select Rebuild All from the Make

menu, you will still get a non-overlaid program because PWB

normally builds the first target in the MAKE file. To build the

overlaid program, modify the command line passed to NMAKE so that

NMAKE builds your overlay target rather than the regular EXE.

Choose NMAKE Options from the Options menu and specify "OVERLAID"

as the target by putting it in the NMAKE options box, or use

Build Target from the Make menu.

5. By choosing NMAKE Options from the Options menu and specifying

"OVERLAID", you can build your program by either choosing Rebuild

All or Build *.EXE from the Make menu, as usual. If you want to

build a non-overlaid program, delete "OVERLAID" from the NMAKE

options box.

Note that if you use debug options with overlays you will get a

linker warning L4047. This warning, and the dialog box that says

that CRT0DAT.ASM can't be found, are normal when building overlaid

programs for debugging and can be ignored. You can debug the

overlaid program normally, with full debugging information

available.

This MAKE file behaves almost identically to a regular PWB MAKE

file. The only differences are that NMAKE options are NOT passed to

the browser build unless you add them to the browser build line,

and that you must edit the user supplied section if you add or

delete modules from the project.

Additional reference words: 1.00 1.10