- What is DJGPP
- Setup DJGPP
- Building Newth
- After building
DJGPP is a port of GNUs C/C++/Fortran compilers to DOS systems. It can be used to build i386 compatible binaries on DOS, for DOS. DJGPP cross compilers to build from typical modern systems are also available.
Note: Building Newth with DJGPP is considered experimental due to the Watt32 library requirement
To build Newth with DJGPP you will need the following:
- 80386 compatible machine or emulator
- DOS 4.0+ operating system or emulator
- DJGPP v2.05
- GNU Mtools (optional)
- UPX binary compression (optional)
- Watt32 library compiled with the same version of DJGPP
Tip: If hardware isn't available it's possible to proceed with a emulator such as Dosbox-X
Installation instructions for DJGPP differ depending on the build machines operating system. Some common operating systems are listed in the table below:
| Operating System | Installation Instructions |
|---|---|
| FreeDOS | Load the bonus CD/ISO then run FDIMPLES, navigate to the Development group and check DJGPP, DJGPP_BN, DJGPP_GC & DJGPP_MK for installation |
| Linux | Install and configure a DJGPP cross compiler |
| MacOS | Install and configure a DJGPP cross compiler |
| SvarDOS | Run PKGNET pull djgpp, PKGNET pull djgpp_bn, PKGNET pull djgpp_gc and PKGNET pull djgpp_mk or download manually then run PKG install djgpp.svp, PKG install djgpp_bn.svp, PKG install djgpp_gc.svp and PKG install djgpp_mk.svp |
| Windows | Install and configure a DJGPP cross compiler |
If you already have a packet driver setup on your DOS system then it is relatively straight forward to setup the SvarDOS
package manager. .SVP files are normal zip files so it should be possible to bootstrap the SvarDOS repository by
extracting PKG.EXE and moving it and PKGNET.SVP onto the system. After which you can use PKG.EXE to install
PKGNET.SVP to download PKG.SVP to install.
Make sure the network packet driver is loaded and both %DOSDIR% & %PATH% are set correctly then run the following:
PKG.EXE install PKGNET.SVP
PKGNET pull pkg
PKG.EXE install PKG.SVP
Optionally, remove the extracted PKG.EXE and .SVP files to free disk space:
DEL PKG.EXE
DEL *.SVP
The DJGPP build environment needs to be setup before it can be used.
On a typical DOS installation of DJGPP run the following to enable the build environment.
Note: the following steps will need to be repeated each time DOS boots. If this system is using DJGPP frequently consider making the following commands part of your
AUTOEXEC.BAT/FDAUTO.BATscript
SET PATH=%PATH%;%DOSDIR%\DEVEL\DJGPP\BIN
SET DJGPP=%DOSDIR%\DEVEL\DJGPP\DJGPP.ENV
Tip:
gccshould now be valid commands if this isn't the case check the directories in the script and modify them as necessary.
Assuming the DJGPP cross compiler tarball was extracted to /opt run the following to setup DJGPP in your shell
export PATH=/opt/djgpp/i586-pc-msdosdjgpp/bin/:/opt/djgpp/bin/:$PATH
export GCC_EXEC_PREFIX=/opt/djgpp/lib/gcc/
export DJDIR=/opt/djgpp/i586-pc-msdosdjgpp
Newth on DOS depends on Watt32. The Watt32s folder should be extracted on symlinked
into the directory containing makefile so that it looks like so.
DJGPP\makefile
DJGPP\Watt32s\inc
DJGPP\Watt32s\lib
Newth depends on BSD-like networking API and compiling for DOS is no exception.
For Newth to link to Watt32 correctly USE_BSD_API must be defined when building Watt32 library.
It's optional but a good idea to define USE_BOOTP and/or USE_DHCP
so that Newth can configure its IP address automatically.
To do this Watt32s\src\config.h has to be manually modified like so:
#undef USE_DEBUG
#undef USE_MULTICAST
#undef USE_BIND
-#undef USE_BSD_API
+#define USE_BSD_API
#undef USE_BSD_FATAL
-#undef USE_BOOTP
-#undef USE_DHCP
+#define USE_BOOTP
+#define USE_DHCP
#undef USE_RARP
#undef USE_GEOIP
#undef USE_IPV6
#undef USE_LANGUAGE
#undef USE_FRAGMENTS
#undef USE_STATISTICS
#undef USE_STACKWALKER
#undef USE_FSEXTCaution: some versions of watt-32 have a broken implementation of DHCP that can cause an infinite loop. On a real DOS this means it could very well lock up the computer with no option but to hard reset. If in doubt leave
USE_DHCPundefined. Most DHCP servers are backwards compatible with BOOTP.
Run make to build the project.
Two 32-bit binaries called dl.exe and th.exe will be made that can be run from any path (including a floppy
diskette)
on any DOS computer with a DPMI server running on a 80386 compatible CPU with a 80387 compatible FPU.
A DOS Protected Mode Interface (DPMI) server is a utility that allows real mode DOS to extend itself with protected mode features of the 80386 and later processors.
Like all 32-bit DOS executables DJGPP binaries need a DPMI server to run. FreeDOS and Windows 95 setup their own DPMI
server by default and no further files are needed on these systems. If your system doesn't include it's own DPMI server
then CWSDPMI can be used which is the DJGPP equivalent to Watcoms DOS4GW.EXE.
| Operating System | Installation Instructions |
|---|---|
| SvarDOS | Run PKGNET pull cwsdpmi or download manually then run PKG install cwsdpmi.svp |
There are two ways to use Cwsdpmi. Which way is better depends on the circumstances of the user and system.
Both methods assume that you're in the same directory as DL.EXE and TH.EXE and that cwsdpmi.svp has been
installed in it's default directory.
Similar to DOS4GW.EXE for Watcom built applications.
CWSDPMI.EXE can be placed in the same directory as the an EXE to make it start.
Several DJGPP binaries in the same directory can make use of the same CWSDPMI.EXE which can save some disk space.
COPY %DOSDIR%\PROGS\CWSDPMI\CWSDPMI.EXE .
CWSDPMI.EXE can be baked into DL.EXE and TH.EXE so that no external files are needed to start the program.
This is much more ideal for executables that are intended for portable use.
COPY %DOSDIR%\PROGS\CWSDPMI\CWSDSTUB.EXE .
MOVE dl.exe dlnostub.exe
exe2coff dlnostub.exe
COPY /B CWSDSTUB.EXE+dlnostub dl.exe
MOVE th.exe thnostub.exe
exe2coff thnostub.exe
COPY /B CWSDSTUB.EXE+thnostub th.exe
On DOS machines disk space is usually at a premium. Even though the release builds are stripped of all debugging symbols it is possible to make the binary take substantially less disk space with UPX compression so that it fits comfortably on a smaller diskette standard.
| Build | UPX command | Fits on |
|---|---|---|
| DJGPP | UPX dl.exe --best |
5¼-inch QD (720k) |
| DJGPP | UPX dl.exe th.exe --best |
5¼-inch HD (1200k) |
On a real DOS machines it makes sense to directly copy the new binaries onto a newly formatted diskette. Conversely when cross compiling or distributing over the Internet it may make more sense to distribute as a floppy disk image so that users can make their own disks locally. This can be achieve with GNU Mtools.
Note: At the time of writing there's no DOS port of GNU Mtools. The newly created binaries will need to be transferred to a more modern Linux or Windows machine to use Mtools on them.
With compression the binaries will fit much better into diskette image then they otherwise would, in some cases becoming compatible with a lower standard of diskette. While there might be a lot of free space after copying the files to the image users may want to put other files on the disk (such as WatTCP configuration and/or a network packet driver) and a real diskette may contain bad sectors.
With Mtools installed, create a diskette image with mformat then copy the binaries to the new image with mcopy.
Below are some example configurations.
Tip: If you can only spare one diskette which can't fit both programs on it. You could write
DL.EXEand a packet driver to the disk then use these to downloadTH.EXEover the network.
mformat -C -i dldj_720.ima -v "DLDJ" -f 720
mcopy -i dldj_720.ima DL.EXE ::mformat -C -i thdj_720.ima -v "THDJ" -f 720
mcopy -i thdj_720.ima TH.EXE ::mformat -C -i newth1.2.ima -v "NEWTH DJ" -f 1200
mcopy -i newth1.2.ima DL.EXE TH.EXE ::mformat -C -i dldj_1.4.ima -v "DLDJ" -f 1440
mcopy -i dldj_1.4.ima DL.EXE ::mformat -C -i thdj_1.4.ima -v "THDJ" -f 1440
mcopy -i thdj_1.4.ima TH.EXE ::mformat -C -i newth2.8.ima -v "NEWTH DJ" -f 2880
mcopy -i newth2.8.ima DL.EXE TH.EXE ::