diff --git a/2018/burton1/README.md b/2018/burton1/README.md index 0be1b77b4..ee09acc7b 100644 --- a/2018/burton1/README.md +++ b/2018/burton1/README.md @@ -4,6 +4,9 @@ make ``` +There is an alternate version of this entry. See [Alternate +code](#alternate-code) below. + ## To use: @@ -15,8 +18,7 @@ make ### Try: ```sh -./prog < prog -./prog < prog.c +./try.sh ``` @@ -24,15 +26,23 @@ make An alternate version of this entry, [prog.alt.c](prog.alt.c), is provided This alternate code was supposed to compile without warnings, however -with modern compilers this is no longer the case. +with modern compilers this is no longer the case so it will only cleanly compile +with `-Wno-` options. + + +### Alternate build: -To compile this alternate version: ```sh make alt ``` +### Alternate use: + +Use `prog.alt` as you would `prog`. + + ## Judges' remarks: One line, one array, one loop and one statement but it prints many bytes. It won. @@ -40,9 +50,9 @@ One line, one array, one loop and one statement but it prints many bytes. It won ## Author's remarks: -Feed this anything on stdin. +Feed this anything on `stdin`. -The [included script](scripthd) may be used as a driver program for this entry. +The [included script.sh](scripthd.sh) may be used as a driver program for this entry. It adds several nice-to-have features, and allows salt-to-taste customizability. This code has been compiled and tested on: @@ -51,21 +61,24 @@ This code has been compiled and tested on: * X86-Linux, gcc 4.1.2 and 4.8.4, -O0 and -O3 * ARM-QEMU, gcc 4.8.4, -O0 and -O3 * X86-FreeBSD 10.3, clang 3.4.1, -O0 and -O3 -* TCC 0.9.26 (x86-64) (used as a proxy for [2001/bellard](http://ioccc.org/years.html#2001_bellard)) +* TCC 0.9.26 (x86-64) (used as a proxy for [2001/bellard](/years.html#2001_bellard)) * UNIX V7 pcc (Johnson's C compiler) on a [simulated PDP-11/45](http://simh.trailing-edge.com/) (see spoiler for further detail)
Spoiler below; scroll down.
+ ### SPOILER: -This started life as a personal challenge: write the shortest hex dump utility in C. +This started life as a personal challenge: write the shortest hex dump utility +in C. The self-imposed ground rules in the hunt for shortest: -- the code has to output correctly, -- no extraneous newlines, the code must be portable, -and without bypassing the solution using execve(2), or functions built upon it (system(3), popen(3), etc). +- The code has to output correctly. +- No extraneous newlines, the code must be portable, +and without bypassing the solution using `execve(2)`, or functions built upon it +(`system(3)`, `popen(3)`, etc). E.g: @@ -155,8 +168,10 @@ $ ``` An obfuscated hex dump has been done before: -[1986/bright/bright.c](http://ioccc.org/1986/bright/bright.c) is similar in function, -but it uses more characters in just setting up its obfuscation than this entire solution! +[1986/bright](/1986/bright/README.md) is similar in function, +but it uses more characters in just setting up its obfuscation than this entire +solution! + ### BIGGER SPOILER: @@ -165,12 +180,13 @@ replace the cryptic expression `4<(4^l>>5)?l:46` with `32>l|l>126?46:l`. Both take the same number of characters, but the former is a bit more interesting. Bonus question: how does the first expression work? + ### BIGGEST SPOILER (and some history): Technically, `char o[0];` is illegal (SS 6.7.6.2) according to ISO (N1570). And `char o[];` is a conditionally supported feature (SS 6.7.6.2, 6.10.8.3). However, it works in modern C implementations as an extension, including GCC, -Clang and TCC, for X86 and ARM, on multiple operating systems (Linux, OSX, +Clang and TCC, for X86 and ARM, on multiple operating systems (Linux, OSX/macOS, FreeBSD), so it is _functionally_ correct. MicroSoft Visual C++ does not allow `char o[]` or `char o[0]`, and implements its close relative `char o[1]` such that writing more than a single char will cause a fault, which is _technically_ @@ -185,7 +201,8 @@ bytes following `O`, addressed via `o`, and this code only needs 17. This is _undefined_ behavior, but as shown, it is widely available. The [1979 Seventh Edition UNIX][1] (v7) system pre-dates the IOCCC by several years, -and the source code to `sh`(1) was a [significant inspiration for this contest][2]. +and the source code to `sh`(1) was a [significant inspiration for this +contest](/all/README.md). There are two C compilers present: `cc` written by Dennis Ritchie, and `pcc` written by Steven Johnson. The nested conditional expressions in 116 and smaller are too complex for `cc` ("Illegal conditional") but `pcc` handles them correctly, and neither compiler accepts `char o[]` or @@ -194,9 +211,9 @@ not yet written for UNIX). [1]: http://minnie.tuhs.org/cgi-bin/utree.pl [2]: http://ioccc.org/all/README -[3]: https://web.archive.org/web/20180521074522/http://www.computerworld.com.au/article/279011/a-z_programming_languages_bourne_shell_sh/?pp=4 +[2]: https://web.archive.org/web/20180521074522/http://www.computerworld.com.au/article/279011/a-z_programming_languages_bourne_shell_sh/?pp=4 -More significant is that v7 `printf`(3) does not report the number of characters +More significant is that v7 `printf(3)` does not report the number of characters written, and therefore 111 compiles but does not work correctly; 113 is the shortest code that compiles and runs correctly in Ancient UNIX. @@ -216,7 +233,7 @@ page 71, remarks: It is fascinating to explore the roots of C through the history of the operating system it was birthed within. C is often criticized as a difficult, inscrutable language, but as this contest demonstrates, this is in parody. _Shell-gol_ is -one of those instances where someone [preferred a different language][3], and +one of those instances where someone [preferred a different language][2], and (ab)used the preprocessor to re-mold C into something they found comfortable. Most of the rest of the system, especially in the kernel, are models of clarity and efficient expression. @@ -247,6 +264,12 @@ Try: cat prog.c prog.alt.c ``` +or + +```sh +cmp -b prog.c prog.alt.c +``` + to compare the differences (`diff` is not helpful on a one-liner). diff --git a/2018/burton1/scripthd b/2018/burton1/scripthd.sh similarity index 100% rename from 2018/burton1/scripthd rename to 2018/burton1/scripthd.sh diff --git a/2018/burton1/try.sh b/2018/burton1/try.sh new file mode 100755 index 000000000..6deb1b5cb --- /dev/null +++ b/2018/burton1/try.sh @@ -0,0 +1,39 @@ +#!/usr/bin/env bash +# +# try.sh - demonstrate IOCCC winner 2018/burton1 +# + +# make sure CC is set so that when we do make CC="$CC" it isn't empty. Doing it +# this way allows us to have the user specify a different compiler in an easy +# way. +if [[ -z "$CC" ]]; then + CC="cc" +fi + +make CC="$CC" everything >/dev/null || exit 1 + +for i in prog scripthd.sh; do + echo "$ ./$i < prog.c" 1>&2 + ./"$i" < prog.c + echo 1>&2 + + read -r -n 1 -p "Press any key to run: ./$i < prog (space = next page, q = quit): " + echo 1>&2 + ./"$i" < prog | less -EXF + echo 1>&2 + + read -r -n 1 -p "Press any key to run: ./$i < scripthd.sh (space = next page, q = quit): " + echo 1>&2 + ./"$i" < scripthd.sh | less -EXF + echo 1>&2 + + + read -r -n 1 -p "Press any key to run: head $0 | ./$i: " + echo 1>&2 + head "$0" | ./"$i" + echo 1>&2 + + read -r -n 1 -p "Press any key to run: tail -n 15 Makefile | ./$i: " + echo 1>&2 + tail -n 15 Makefile | ./"$i" +done