mirror/ioccc
1
0 Fork 0
Code Issues Pull Requests Actions Packages Projects Releases Wiki Activity

Format and typo fixes to 1984 README.md files

Browse Source 
I paid a lot of attention to 1984/mullender partly because it is one of
Landon's all time favourite entries to this day and partly because it
felt like it was a good idea especially as there is a lot of
instructional value in the author's remarks that I located a while back.
However this did take quite some time so I probably won't do that for
many more entries if any more as it will slow things down tremendously.
There was an unfortunate typo fix in this README.md too: a typo in the
file, possibly a typo from the copy paste (think I copied from an image
but it might have been a pdf too in which case the original person
adding the remarks in the book cited made a typo / copy-pasted the
information from the author), which could cause confusion when reading
the remarks.
This commit is contained in:
Cody Boone Ferguson committed 2023-07-10 04:37:03 -07:00
1 parent 1d86daf19a
commit b97fd81cc0
4 files changed
+190 -121
Download Patch File Download Diff File Expand all files Collapse all files

No files matched your search

1984/anonymous/README.md
+3 -1
View File
@@ -37,6 +37,7 @@ NOTE: this version might not work on some systems like macOS.
./anonymous.alt
```
## Judges' remarks:
The author was too embarrassed that they could write such trash, so I
@@ -55,7 +56,6 @@ for more information on the tattoo. Along with the code, this is what it looks l
![1984-anonymous-tattoo.jpg](1984-anonymous-tattoo.jpg)
## Author's remarks:
### On remaining anonymous:
@@ -66,6 +66,7 @@ wished to remain anonymous and they said:
> Yes, I want to keep my anonymity. But you can tell them that I am well known
for my connection to the C language.
### On the famous tattoo (see above):
The author, when told about this tattoo, said:
@@ -77,6 +78,7 @@ Landon Curt Noll, the one who told the author about the tattoo, wrote back:
> Yes, to our knowledge it is.
### Regrets:
Landon Curt Noll wrote that the author, if they had to do it over again, regrets not
1984/decot/README.md
+5
View File
@@ -2,18 +2,21 @@
Dave Decot
## To build:
```sh
make all
```
## To run:
```sh
./decot
```
### Alternate code:
To try the original code that requires `-traditional-cpp`:
@@ -30,6 +33,7 @@ This program prints out a string of garbage.
The judges also offer this one comment: understand remarks!
### Historical remarks:
Some new (in 1984) compilers disliked line 15 of the original source, so we changed it
@@ -48,6 +52,7 @@ for(signal=0;*k *x * __FILE__ *i;) do {
To see what we mean look at the [original source file](decot.orig.c).
## Author's remarks:
No remarks were provided by the author.
1984/laman/README.md
+2 -2
View File
@@ -18,12 +18,12 @@ make all
### INABIAF - it's not a bug it's a feature :-)
This entry will very likely crash or do something else if you run it without an
arg.
arg. It likely won't do anything at all if the arg is not a positive number.
## Try:
The program accepts ONE POSITIVE argument. Seeing is believing, so try things
The program accepts ONE POSITIVE number. Seeing is believing, so try things
like:
```sh
1984/mullender/README.md
+180 -118
View File
@@ -5,28 +5,33 @@ Sjoerd Mullender<br />
Robbert van Renesse
## To build:
```sh
make all
```
## To run:
```sh
./mullender
```
> NOTE: If your machine is not a VAX-11 or PDP-11, this program will
> not execute correctly. In later years, machine dependent
> code was discouraged.
> NOTE: If your machine is not a [VAX-11](https://en.wikipedia.org/wiki/VAX-11)
or [PDP-11](https://en.wikipedia.org/wiki/PDP-11), this program will not execute
correctly. In later years, machine dependent code was discouraged.
### Alternate code:
[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) added the alternative
code which lets you run this on other systems. He notes though that this was
only a slight fix and enhancement to the change in the [faq](/faq.md). Thank you
Cody for your assistance!
An alternate version exists which allows one to enjoy this entry on systems
other than a [VAX-11](https://en.wikipedia.org/wiki/VAX-11) or
[PDP-11](https://en.wikipedia.org/wiki/PDP-11). This version has a delay feature
as it goes so fast in modern systems. The author later suggested that there was
a delay in the original system as well.
#### To build:
@@ -35,6 +40,7 @@ Cody for your assistance!
make alt
```
#### To run:
```sh
@@ -48,8 +54,8 @@ too fast.
BTW: is there such a thing as too fast a CPU ? :-) Actually yes for certain code
which is probably not as uncommon as you think :-).
Note that it is an int and it uses `atoi()` which does NOT check for
overflow! In fact it's argc itself.
Note that it is an `int` (argc) and it uses `atoi()` which does NOT check for
overflow!
#### Try:
@@ -67,39 +73,38 @@ overflow! In fact it's argc itself.
./mullender.alt 100000
```
What happens if you hit enter after it writes a line of output?
## Judges' remarks:
Without question, this C program is the one of the most obfuscated
C program that has ever been received! Like all great contest
entries, they result in a change of rules for the following year.
To prevent a flood of similar programs, we requested that programs
be non machine specific.
Without question, this C program is the one of the most obfuscated C program
that has ever been received! Like all great contest entries, it resulted in a
change of rules for the following year. To prevent a flood of similar programs,
the rules were changed, requesting non-machine specific code.
This program was selected for the 1987 t-shirt collection.
The C startup routine (via crt0.o) transfers control to a location
named main. In this case, main just happens to be in the data area.
The array of shorts, which has been further obfuscated by use of
different data types, just happens to form a meaningful set of PDP-11
and Vax instructions. The first word is a PDP-11 branch instruction
that branches to the rest of the PDP code. On the Vax main is called with
the calls instruction which uses the first word of the subroutine as a
mask of registers to be saved. So on the Vax the first word can be anything.
The real Vax code starts with the second word. This small program
makes direct calls to the write() Unix system call to produce a
message on the screen. Can you guess what is printed? We knew you
couldn't! :-)
The C startup routine (via `crt0.o`) transfers control to a location named main.
In this case, main just happens to be in the data area. The array of shorts,
which has been further obfuscated by use of different data types, just happens
to form a meaningful set of [PDP-11](https://en.wikipedia.org/wiki/PDP-11) and
Vax instructions. The first word is a
[PDP-11](https://en.wikipedia.org/wiki/PDP-11) branch instruction that branches
to the rest of the [PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor) code. On the Vax main is called with the calls
instruction which uses the first word of the subroutine as a mask of registers
to be saved. So on the Vax the first word can be anything. The real Vax code
starts with the second word. This small program makes direct calls to the
write() Unix system call to produce a message on the screen. Can you guess what
is printed? We knew you couldn't! :-)
BTW: this remains my (Landon Curt Noll's) all time favorite entries!
Cody found the remarks from [Sjoerd Mullender](/winners.html#Sjoerd_Mullender)
and added the program that was used by the authors to generate the array that he
What happens if you hit enter after it writes a line of output?
In 2023 remarks were discovered from [Sjoerd Mullender](/winners.html#Sjoerd_Mullender)
and so was the program that was used by the authors to generate the array that he
referred to. Because [a.out.h](a.out.h) is not available in all systems (like macOS) and
more importantly because he wanted it to be as close to as the original as
possible he used a copy of
more importantly because we wanted it to be as close to as the original as
possible we used a copy of
<https://raw.githubusercontent.com/dspinellis/unix-history-repo/Research-Release/usr/include/a.out.h>
in the *fabulous* [Unix History
Repo](https://github.com/dspinellis/unix-history-repo/tree/Research-Release).
@@ -111,16 +116,17 @@ This tool can be built by running:
make gentab
```
Cody notes that it does not appear to work in modern systems (unbalanced braces)
We note that it does not appear to work in modern systems (unbalanced braces)
or something else is wrong but given that this was done a long time ago on a now
archaic system maybe that is why. He also noted that if the `short`s are not
archaic system maybe that is why. We also note that if the `short`s are not
changed to just `int` it prints out a lot of negative numbers but since
[mullender.c](mullender.c) has a negative number he kept it as is.
[mullender.c](mullender.c) has a negative number we kept it as is.
Thank you Cody!
## Author's remarks:
### Notes from the judges:
These remarks, found at
[https://lainsystems.com/posts/exploring-mullender-dot-c/](https://lainsystems.com/posts/exploring-mullender-dot-c/),
were provided by Sjoerd Mullender years later. We thank the author of the
@@ -128,71 +134,92 @@ article for the quote! For a more detailed analysis, taken from the Obfuscated C
and Other Mysteries, see below. We hope that this is okay with the author of the
book. Considering that the analysis is entirely the authors' comments we don't
think this will be a problem. Unfortunately the excerpt was PDF and it did not
copy paste well. [Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) had to
go back and forth to type so it's possible he made a typo though he also fixed
some typos found in the extract. As for the other comments:
copy paste well. We had to go back and forth to type so it's possible he made a
typo though he also fixed some typos found in the extract. As for the other
comments:
## Remarks from the author:
I have never known a lot about the VAX assembly, so we used the C compiler to
create the VAX code. We didn't write it ourselves from scratch as we did with
the PDP code. This is the reason why the VAX code is more complex, including the
extra data after the PDP code.
I have never known a lot about the [VAX](https://en.wikipedia.org/wiki/VAX)
[assembly](https://en.wikipedia.org/wiki/Assembly_language), so we used the C
compiler to create the VAX code. We didn't write it ourselves from scratch as we
did with the [PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor)
code. This is the reason why the [VAX](https://en.wikipedia.org/wiki/VAX) code
is more complex, including the extra data after the
[PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor) code.
Robbert and I were students at the VU (Free University in Amsterdam) at the time
(mathematics with CS as our major since there was no CS curriculum when we
started). We had an assignment to create a pair of programs for the computer
networks course. The programs were supposed to send data reliably from one
program to the other over an unreliable channel. This channel was simulated with
a pair of pipes.
Robbert and I were students at the [VU (Free University in
Amsterdam)](https://vu.nl/en) at the time (mathematics with CS as our major
since there was no CS curriculum when we started). We had an assignment to
create a pair of programs for the computer networks course. The programs were
supposed to send data reliably from one program to the other over an unreliable
channel. This channel was simulated with a pair of
[pipes](https://en.wikipedia.org/wiki/Pipeline_(software)).
We decided for fun to create an obfuscated set of programs, only for the PDP, to
do this, but circumventing the channel. (I.e. cheating, hence the needed
obfuscation.) Our programs worked and we handed them in.
We decided for fun to create an
[obfuscated](https://en.wikipedia.org/wiki/Obfuscation_(software)) set of
programs, only for the
[PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor), to do this, but
circumventing the channel. (I.e. cheating, hence the needed obfuscation.) Our
programs worked and we handed them in.
Of course, the teacher had a good laugh and then rejected our submission. (We
knew him well, so we could get away with this.)
Then the IOCCC came along. I don’t remember how we heard about it, but at the
time there was a world-wide messaging network Usenet where we read a bunch of
newsgroups. I’m sure it was announced there and we saw it.
Then the [IOCCC](https://www.ioccc.org) came along. I don’t remember how we
heard about it, but at the time there was a world-wide messaging network Usenet
where we read a bunch of newsgroups. I’m sure it was [announced
there](https://groups.google.com/g/net.lang.c/c/lx-TAuEyeRI/m/HdOOnNx6LC0J) and we saw
it.
Since we had just recently created these obfuscated programs we decided we could
Since we had just recently created these [obfuscated
programs](https://en.wikipedia.org/wiki/Obfuscation_(software))) we decided we could
use the same technique for an obfuscated C program. We upped the ante a bit by
making it “portable”.
making it "portable".
To add to the obfuscation, we used different formats for the integers in the
array, some in decimal, some in octal, some in hexadecimal, and when the value
would fit, some as an ASCII character.
To add to the
[obfuscation](https://en.wikipedia.org/wiki/Obfuscation_(software))), we used
different formats for the integers in the array: some in decimal, some in octal,
some in hexadecimal, and when the value would fit, some as an ASCII character.
The rest is history.
Since this was the first contest, we hadn't seen any old entries, nor had any of
the other contestants. Of course we knew about `#define` and tricks you could do
with that, but we didn't need that for this program. In fact, we made it as
“standard” as possible. At the time there was this program called `cb` for C
beautifier which would re-indent your program to make the layout look better. Our
program is idempotent under `cb`.
"standard" as possible. At the time there was this program called `cb` or C
beautifier which would re-indent your program to make the layout look better.
Our program is idempotent under `cb`.
### More detailed analysis
When this program is compiled, the compiler places the array somewhere in
memory, just like it places any compiled code somewhere in memory. Usually, the
C startup code (`crt0.o`) calls a routine named `main`. The loader fills in the address in
the startup code, but, at least on the old systems where this program
ran, it doesn't know that the `main` in this program isn't code but data!
C startup code (`crt0.o`) calls a routine named `main()`. The loader fills in the
address in the startup code, but at least on the old systems where this program
rans, it doesn't know that the `main()` in this program isn't code but data!
When the program is run, the C startup code transfers control to the location
`main`. The contents of the array just happen to be machine instructions for
both a PDP-11 and a VAX.
both a [PDP-11](https://en.wikipedia.org/wiki/PDP-11) and a
[VAX](https://en.wikipedia.org/wiki/VAX).
On the VAX, the routine main is called with the `calls` instruction. This
instruction uses the first (2-byte) word of the called routine as a mask of
registers that are to be saved on the stack. In other words, on the VAX the
first word can be anything. On the PDP, the first word is a branch instruction
On the [VAX](https://en.wikipedia.org/wiki/VAX), the routine `main()` is called
with the `calls` instruction. This instruction uses the first (2-byte)
[word](https://en.wikipedia.org/wiki/Word_(computer_architecture)) of the called
routine as a mask of
[registers](https://en.wikipedia.org/wiki/Processor_register) that are to be
saved on the [stack](https://en.wikipedia.org/wiki/Stack_(abstract_data_type)).
In other words, on the VAX the first word can be anything. On the
[PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor), the first word
is a [branch](https://en.wikipedia.org/wiki/Branch_(computer_science))
[instruction](https://en.wikipedia.org/wiki/Instruction_set_architecture#Instructions)
that branches over the VAX code. The PDP and VAX codes are thus completely
separate.
The PDP and VAX codes implement the same algorithm:
The [PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor) and
[VAX](https://en.wikipedia.org/wiki/VAX) codes implement the same algorithm:
```c
for (;;) {
@@ -201,20 +228,26 @@ The PDP and VAX codes implement the same algorithm:
}
```
The result is that the symbols `:-)` move over the screen. `delay` is
implemented differently on the PDP, where we used a nonexistent system call
(`sys 55`), and on the VAX where we used a delay loop.
The result is that the symbols `:-)` move across the screen. `delay` is
implemented differently on the
[PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor), where we used a
nonexistent system call (`sys 55`), and on the
[VAX](https://en.wikipedia.org/wiki/VAX) where we used a delay loop.
My co-author, Robbert, and I had earlier written a similar program for an
assignment on the PDP-11. Along came the first Obfuscated C Code Contest, and
assignment on the [PDP-11](https://en.wikipedia.org/wiki/PDP-11). [Along
came](https://groups.google.com/g/net.lang.c/c/lx-TAuEyeRI/m/HdOOnNx6LC0J) the
first [Obfuscated C Code Contest](https://www.ioccc.org), and
we decided that we should write a program like this, but make it run on two
different architectures.
different [architectures](https://en.wikipedia.org/wiki/Computer_architecture).
We didn't think long about what the program should do, so it does something very simple.
We didn't think long about what the program should do, so it does something very
simple.
We started with writing the PDP code in assembler. We both knew PDP-11
assembler, so that was no problem. The assembler code we came up with is as
follows:
We started with writing the
[PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor) code in assembly.
We both knew [PDP-11](https://en.wikipedia.org/wiki/PDP-11) assembly so that was
no problem. The assembly code we came up with is as follows:
```asm
pdp:
@@ -232,24 +265,35 @@ pdp:
```
This is not the code we originally wrote, but it is the code that we ultimately
used in the program. The string to be printed is shared by the VAX and the PDP
used in the program. The string to be printed is shared by the
[VAX](https://en.wikipedia.org/wiki/VAX) and the
[PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor)
code and is located between the two sections.
First, the program deals with figuring out the address of the string. Then the
program counter is saved in a scratch register. Since the program counter points
at the second instruction, we subtract 2 from the scratch register in the second
instruction. Then we subtract the length of the string and store the result in
the location with label 0. This has to do with the calling sequence of system
calls on the PDP. Following the `sys` instruction is the system call number (4
for `write`), the address of the buffer (pointed to by label 0), and the length
of the buffer (9). The file descriptor is in register `r0`. The rest of the code
implements a delay loop. In each iteration, a non-existing system call (55)
slows things down.
[program counter](https://en.wikipedia.org/wiki/Program_counter) is saved in a
scratch [register](https://en.wikipedia.org/wiki/Processor_register). Since the
program counter points at the second
[instruction](https://en.wikipedia.org/wiki/Instruction_set_architecture#Instructions),
we subtract 2 from the scratch register in the second instruction. Then we
subtract the length of the string and store the result in the location with
label 0. This has to do with the calling sequence of [system
calls](https://en.wikipedia.org/wiki/System_call) on the
[PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor). Following the
`sys` instruction is the system call number (4 for `write()`), the address of
the buffer (pointed to by label 0), and the length of the buffer (9). The [file
descriptor](https://en.wikipedia.org/wiki/File_descriptor) is in register `r0`.
The rest of the code implements a delay loop. In each iteration, a non-existing
system call (55) slows things down.
We assembled this program and extracted the machine code from the resulting
object file. We used this code in the VAX part. Since neither of us was fluent
in VAX assembly, we wrote the VAX code in C and massaged the compiler output.
The VAX assembly program that we came up with is as follows:
We assembled this program and extracted the [machine
code](https://en.wikipedia.org/wiki/Machine_code) from the resulting [object
file](https://en.wikipedia.org/wiki/Object_file). We used this code in the
[VAX](https://en.wikipedia.org/wiki/VAX) part. Since neither of us was fluent in
VAX [assembly](https://en.wikipedia.org/wiki/Assembly_language), we wrote the
VAX code in C and massaged the
[compiler](https://en.wikipedia.org/wiki/Compiler) output. The VAX assembly
program that we came up with is as follows:
```asm
@@ -275,25 +319,40 @@ str: .ascii " :-)\b\b\b\b"
pdp: .word 4548, 3044, 58820, 9, 4407, 6, 5568, 1, 35076, 0, 9, 5570, 512, 35117, 32386, 496
```
The first word (after the label `vax`) is the PDP branch instruction. PDP branch
The first word (after the label `vax`) is the
[PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor) [branch
instruction](https://en.wikipedia.org/wiki/Branch_(computer_science)).
[PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor) branch
instructions are octal `400+` the distance divided by 2. The string that both
the PDP and VAX programs use is after the `str` label, and the PDP code is after
the pap label.
the [PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor) and
[VAX](https://en.wikipedia.org/wiki/VAX)
programs use is after the `str` label, and the
[PDP](https://en.wikipedia.org/wiki/Programmed_Data_Processor) code is after the
pdp label.
On the VAX, the program pushes 9 (the length of the string), the address of the
string and 1 (the file descriptor) on the stack and calls `write`. Since we
didn't know the exact calling sequence for system calls, we just copied the
source for the `write` system call stub into our program. After `write`
finishes, the program executes a delay loop, after which it jumps back to the
start of the program.
On the [VAX](https://en.wikipedia.org/wiki/VAX), the program
[pushes](https://en.wikipedia.org/wiki/Stack_(abstract_data_type)) 9 (the length
of the string), the address of the string and 1 (the [file
descriptor](https://en.wikipedia.org/wiki/File_descriptor) on the
[stack](https://en.wikipedia.org/wiki/Stack_(abstract_data_type)) and calls
`write(2)`. Since we didn't know the exact calling sequence for [system
calls](https://en.wikipedia.org/wiki/System_call), we just copied the source for
the `write(2)` system call stub into our program. After `write(2)` finishes, the
program executes a delay loop, after which it jumps back to the start of the
program.
We assembled this program, and extracted the machine code from the object file.
After this we only had to convert the machine code to ASCII and write a little
bit of C to glue everything together. We wanted to use different formats for
each constant in the resulting array, and we wanted to choose the format
randomly. So we wrote a program to choose an appropriate format at random. The
program we wrote for that follows. This program actually also extracted the
machine code from the object file.
We assembled this program, and extracted the [machine
code](https://en.wikipedia.org/wiki/Machine_code) from the [object
file](https://en.wikipedia.org/wiki/Object_file). After this we only had to
convert the machine code to [ASCII](https://en.wikipedia.org/wiki/ASCII) and
write a little bit of C to glue everything together. We wanted to use different
formats for each constant in the resulting array, and we wanted to choose the
format randomly. So we wrote a program to choose an appropriate format at
random. The program we wrote for that follows. This program actually also
extracted the machine code from the object file.
> NOTE from judges: see [gentab.c](gentab.c) for a copy of this file that can be
compiled in modern systems.
```c
#include <stdio.h>
@@ -356,13 +415,16 @@ As can be seen, there is a slight preference for decimal, and also a character
format is sometimes used, but only if the data is a printable ASCII character.
When we ran this program, we were almost completely satisfied with the result.
The only problem we had was that the program had chosen an octal representation
for the first word. Since everybody knows what a PDP-11 branch instruction looks
like (everyone knows that the traditional magic word for an executable, `0407`,
is a PDP-11 branch), we changed that to decimal. After checking the size of the
resulting program we saw that it was one byte too long. The limit was 512 bytes,
and our program was 513 bytes. So we changed the word `and` in the comment to
`&&`.
The only problem we had was that the program had chosen an
[octal](https://en.wikipedia.org/wiki/Octal) representation for the first word.
Since everybody knows what a [PDP-11](https://en.wikipedia.org/wiki/PDP-11)
branch instruction looks like (everyone knows that the traditional magic word
for an executable, `0407`, is a [PDP-11](https://en.wikipedia.org/wiki/PDP-11)
[branch](https://en.wikipedia.org/wiki/Branch_(computer_science)))), we changed
that to decimal. After checking the size of the resulting program we saw that it
was one byte too long. The limit was 512 bytes, and our program was 513 bytes.
So we changed the word `and` in the comment to `&&`.
## Copyright and CC BY-SA 4.0 License: