fix Makefile and README.md for 2001/westley
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@@ -63,14 +63,16 @@ X11_INCDIR= /opt/X11/include
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# Common C compiler warnings to silence
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# Common C compiler warnings to silence
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#
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#
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#CSILENCE=
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#CSILENCE=
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CSILENCE= -Wno-trigraphs -Wno-implicit-function-declaration -Wno-pedantic
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CSILENCE= -Wno-empty-body -Wno-error -Wno-implicit-function-declaration \
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-Wno-implicit-int -Wno-main -Wno-return-type -Wno-trigraphs \
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-Wno-unused-parameter
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# Common C compiler warning flags
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# Common C compiler warning flags
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#
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#
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#CWARN= ${CSILENCE}
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#CWARN= ${CSILENCE}
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#CWARN= -Wall ${CSILENCE}
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#CWARN= -Wall ${CSILENCE}
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#CWARN= -Wall -Wextra ${CSILENCE}
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CWARN= -Wall -Wextra ${CSILENCE}
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CWARN= -Wall -Wextra -pedantic ${CSILENCE}
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#CWARN= -Wall -Wextra -pedantic ${CSILENCE}
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# Compiler standard
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# Compiler standard
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#
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#
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@@ -138,7 +140,9 @@ CC= cc
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#
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#
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ifeq ($(CC),clang)
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ifeq ($(CC),clang)
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#
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#
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CSILENCE+= -Wno-disabled-macro-expansion -Wno-poison-system-directories
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CSILENCE+= -Wno-disabled-macro-expansion -Wno-extra-semi -Wno-missing-prototypes \
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-Wno-missing-variable-declarations -Wno-pedantic \
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-Wno-poison-system-directories -Wno-shadow -Wno-strict-prototypes
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#
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#
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CWARN+= -Weverything
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CWARN+= -Weverything
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#
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#
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+130
-112
@@ -1,4 +1,4 @@
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Best position-independent code:
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# Best position-independent code:
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Brian Westley
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Brian Westley
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Firesign Theatre webmaster
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Firesign Theatre webmaster
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@@ -8,25 +8,30 @@ Best position-independent code:
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http://www.westley.org
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http://www.westley.org
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# To build:
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## To build:
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```sh
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make
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```
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make all
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### To run:
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### To run
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```sh
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././westley
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./westley
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```
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### Try:
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### Try:
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./westley < westley.c > westley2.c
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```sh
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make westley2
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./westley < westley.c > westley2.c
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echo 'Bozos, please deflate shoes before entering the bus!'| ./westley2
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make westley2
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sort -b < westley2.c > westley3.c
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echo 'Bozos, please deflate shoes before entering the bus!'| ./westley2
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make westley3
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sort -b < westley2.c > westley3.c
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./westley3 < westley.c | diff - westley.c
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make westley3
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./westley3 < westley.c | diff - westley2.c
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./westley3 < westley.c | diff - westley.c
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./westley3 < westley.c | diff - westley3.c
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./westley3 < westley.c | diff - westley2.c
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./westley3 < westley.c | diff - westley3.c
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```
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### Alternate code
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### Alternate code
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@@ -34,132 +39,145 @@ An alternate version of this entry, `westley.alt.c`, is provided. This alternat
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To compile this alternate version:
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To compile this alternate version:
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make alt
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```sh
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make alt
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```
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Use `westley.alt` as you would `westley` above.
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Use `westley.alt` as you would `westley` above.
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## Judges' comments
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## Judges' comments
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Try copying the source to a new file and changing around the
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Try copying the source to a new file and changing around the
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order of the lines. Does it produce the exact same output?
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order of the lines. Does it produce the exact same output?
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By changing the order of the source, figure out in how many different
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By changing the order of the source, figure out in how many different
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ways this program can transform input to output.
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ways this program can transform input to output.
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This assortment obfuscated lines takes position-independant code
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This assortment obfuscated lines takes position-independant code
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to a new level! :-)
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to a new level! :-)
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## Author's comments
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## Author's comments
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Punch cards, or Hollerith cards, were becoming obsolete just
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Punch cards, or Hollerith cards, were becoming obsolete just
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as C was becoming more popular*; this is rather unfortunate,
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as C was becoming more popular*; this is rather unfortunate,
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because C has an advantage over many other languages when it
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because C has an advantage over many other languages when it
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comes to punch cards - C programs can be written to be "drop
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comes to punch cards - C programs can be written to be "drop
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proof".
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proof".
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Consider the following C program:
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Consider the following C program:
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main(){a();b();c();}
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```c
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a(){printf("A");}
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main(){a();b();c();}
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b(){printf("B");}
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a(){printf("A");}
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c(){printf("C");}
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b(){printf("B");}
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c(){printf("C");}
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```
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This program will compile and run no matter what order the
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This program will compile and run no matter what order the
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lines are in. If you punch it on cards (one line of code per
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lines are in. If you punch it on cards (one line of code per
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card, naturally) and drop them, you don't need to put them in
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card, naturally) and drop them, you don't need to put them in
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any particular order**; it will always produce "ABC" as output.
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any particular order**; it will always produce "ABC" as output.
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You can also use global variables:
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You can also use global variables:
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char *greet = "Hello, world!";
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```c
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char *greet; main(){puts(greet);}
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char *greet = "Hello, world!";
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char *greet; main(){puts(greet);}
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```
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It would be trivial to write an entire C program that is
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It would be trivial to write an entire C program that is
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"drop proof" using the above techniques; surprisingly, it's
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"drop proof" using the above techniques; surprisingly, it's
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possible to write a program that will always compile but
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possible to write a program that will always compile but
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behave differently depending on the line order:
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behave differently depending on the line order:
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test(a,b){return a;}
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```c
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#define test(a,b) test(b,a)
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test(a,b){return a;}
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main(){if (test(0,1)) printf("T"); else printf("F");}
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#define test(a,b) test(b,a)
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main(){if (test(0,1)) printf("T"); else printf("F");}
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```
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This program will print out "T" if the #define statement
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This program will print out "T" if the #define statement
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falls between the declaration of test() and its use in
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falls between the declaration of test() and its use in
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main(), otherwise it will print out "F". Furthermore,
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main(), otherwise it will print out "F". Furthermore,
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you can use the same call to test() repeatedly in
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you can use the same call to test() repeatedly in
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different lines to return different values:
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different lines to return different values:
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#define test(x,y) test(y,x)
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```c
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main(){int i=0;a(&i);b(&i);c(&i);d(&i);printf("%d\n",i);}
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#define test(x,y) test(y,x)
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a(i)int*i;{if (test(0,1)) *i += 1;}
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main(){int i=0;a(&i);b(&i);c(&i);d(&i);printf("%d\n",i);}
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b(i)int*i;{if (test(0,1)) *i += 2;}
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a(i)int*i;{if (test(0,1)) *i += 1;}
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c(i)int*i;{if (test(0,1)) *i += 4;}
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b(i)int*i;{if (test(0,1)) *i += 2;}
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d(i)int*i;{if (test(0,1)) *i += 8;}
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c(i)int*i;{if (test(0,1)) *i += 4;}
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test(x,y){return x;}
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d(i)int*i;{if (test(0,1)) *i += 8;}
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test(x,y){return x;}
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```
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If you enter the above program on punch cards, throw them
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If you enter the above program on punch cards, throw them
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up in the air, gather them up, and run it, you will get
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up in the air, gather them up, and run it, you will get
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a number from 0 to 15 printed out. Now *that's* a random
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a number from 0 to 15 printed out. Now *that's* a random
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number generator...
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number generator...
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Of course, there are drawbacks to C programming on punch
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Of course, there are drawbacks to C programming on punch
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cards; an 80-character line limit can be restricting, and
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cards; an 80-character line limit can be restricting, and
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(to be maximally portable) you need to use trigraphs for
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(to be maximally portable) you need to use trigraphs for
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the characters "^[]{}\" (these aren't found on every
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the characters "^[]{}\" (these aren't found on every
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keypunch, and have various encodings).
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keypunch, and have various encodings).
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My C program entry does the following:
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My C program entry does the following:
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1) reads in lines
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1) reads in lines
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2) rearranges the lines, or not
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2) rearranges the lines, or not
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2a) if it rearranges the lines, they are sorted or scrambled
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2a) if it rearranges the lines, they are sorted or scrambled
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3) reverses the order of the lines, or not
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3) reverses the order of the lines, or not
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4) prints out the lines as either text or EBCDIC punch cards.
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4) prints out the lines as either text or EBCDIC punch cards.
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The code, as written, scrambles the input and prints it out
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The code, as written, scrambles the input and prints it out
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as normal text, so you can simulate 'dropping' the cards.
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as normal text, so you can simulate 'dropping' the cards.
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You can repeatedly scramble the code to get all 12 variants
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You can repeatedly scramble the code to get all 12 variants
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(but the scrambling isn't very random; it's just a bubble
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(but the scrambling isn't very random; it's just a bubble
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sort with a random number, so some variants are more common
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sort with a random number, so some variants are more common
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than others). You can also just swap the arguments in the
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than others). You can also just swap the arguments in the
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calls to t() in all combinations to get all the variations.
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calls to t() in all combinations to get all the variations.
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If you sort the lines, you will get the version that just
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If you sort the lines, you will get the version that just
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prints out the input as punch cards (you will need to display
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prints out the input as punch cards (you will need to display
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at least 82 columns of text, or clip the last few chars by
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at least 82 columns of text, or clip the last few chars by
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piping it through "sed s/...$//"). If you use this on the
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piping it through "sed s/...$//"). If you use this on the
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original code, you will see that it spells out "HOLLERITH"
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original code, you will see that it spells out "HOLLERITH"
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when punched on cards (you can see the tall, thin letters
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when punched on cards (you can see the tall, thin letters
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spelling out "HOLLERITH" if you turn the C code sideways).
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spelling out "HOLLERITH" if you turn the C code sideways).
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You will also see why "/KC 0000 K" is a "Hollerith emoticon".
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You will also see why "/KC 0000 K" is a "Hollerith emoticon".
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Unrecognized characters are punched as a lace column.
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Unrecognized characters are punched as a lace column.
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(You can see an ASCII simulation of the code as punch cards
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(You can see an ASCII simulation of the code as punch cards
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by looking at card.gif)
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by looking at card.gif)
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For a nice test pattern, try
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For a nice test pattern, try
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&-0123456789ABCDEFGHIJKLMNOPQR/STUVWXYZ:#@'=".<(+|!$*);,%_>?abcmnoxyz^[]{}\
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If you want to analyze the program, sorting the lines while
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```
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ignoring leading blanks works best (sort -b). This will
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&-0123456789ABCDEFGHIJKLMNOPQR/STUVWXYZ:#@'=".<(+|!$*);,%_>?abcmnoxyz^[]{}\
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produce the version that just reverses the line order, and
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```
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the routines in the code are in a sensible order.
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This program should work on EBCDIC computers. It assumes
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If you want to analyze the program, sorting the lines while
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that the time_t ptr param to time() will work with an int
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ignoring leading blanks works best (sort -b). This will
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ptr, and that "passing through" a char[][] array as a simple
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produce the version that just reverses the line order, and
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char* is ok. Your compiler MUST understand trigraphs, or it
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the routines in the code are in a sensible order.
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will miss the trigraph backslash before the double quote in
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the K string and complain about a malformed string; for GNU
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C, use -ansi or -trigraphs. Entering a line of more than 80
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characters, or more than 81 lines, will jam the card reader.
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I've used the a[b] ==> *(a+b) trick, because this is
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This program should work on EBCDIC computers. It assumes
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actually shorter than the trigraph version of a??(b??).
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that the time_t ptr param to time() will work with an int
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ptr, and that "passing through" a char[][] array as a simple
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char* is ok. Your compiler MUST understand trigraphs, or it
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will miss the trigraph backslash before the double quote in
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the K string and complain about a malformed string; for GNU
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C, use -ansi or -trigraphs. Entering a line of more than 80
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characters, or more than 81 lines, will jam the card reader.
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With 28 lines of code (not counting the blank lines or the
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I've used the a[b] ==> *(a+b) trick, because this is
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comment), there are technically 28! different programs, or
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actually shorter than the trigraph version of a??(b??).
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304,888,344,611,713,860,501,504,000,000 different versions,
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all legal C.
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*except in Florida voting machines
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With 28 lines of code (not counting the blank lines or the
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**all cards must be face down, nine-edge first, of course.
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comment), there are technically 28! different programs, or
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304,888,344,611,713,860,501,504,000,000 different versions,
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all legal C.
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*except in Florida voting machines
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**all cards must be face down, nine-edge first, of course.
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