Date:	Tue, 4 Feb 92 15:32:17 EST
From:	DJ Delorie <dj AT ctron DOT com>
To:	ressler AT cs DOT cornell DOT edu
Cc:	djgpp AT sun DOT soe DOT clarkson DOT edu
Subject:	Bootstrapping djgpp
Status:	O

>The mail group discussion on compiling gpp with itself makes me
>wonder how you did it. 

                      - - - History of djgpp - - -

The first step in building djgpp from a dead stop is to get a unix
system based on a 386/PC.  In my case, I used 386/ix from ISC.  I got
the gnu code for gcc and built it, giving me a gnu compiler that ran
on 386/ix and produced 386/ix binaries.  The next step is to replace
all the system calls with special functions by linking in a special .o
just before libc.a that replaced such functions as read(), open(),
exit(), etc.  After building this, I had a version of gcc (et al) that
ran under DOS and produced 386/ix code.  The special functions were
designed to interface with Phar Lap's 386 extender, and I had a
special program that read COFF executables and produced .EXE's.
Special switches were required for the linker to do this without
killing yourself, and a special crt0.o was also required.

Now that I had a program that ran on a PC and created executables that
ran on a PC, the fun part began.  First, I wrote an extender that
could deal with coff files, basically to get rid of the Phar Lap
extender ($$).  I had to do this first because I needed the virtual
memory that Phar Lap at the time didn't support.  I used this extender
to run the compiler in order to compile itself, on a PC, for the first
time.

Now that I could recompile the compiler, the next stage was to switch
back over to the a.out format, which at the time was the native format
for all the GNU programs.  The extender was modified to accept either
coff or a.out format, which I believe it still does, and the compiler
was reconfigured to produce a.out format and recompiled with -O.

After that, I reported 1.39.1 (the first rev was 1.37).  The extender
has had enough functionality added to it so that gcc 2.0 porting was a
breeze (it's not out yet).

So there you have it.

DJ
dj AT ctron DOT com
Life is a banana.

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