Fixes in 1998/schweikh2
There were a number of problems in the README.md that were fixed. A big one was in usage where it said you could run the program and then input a number. Although one could certainly go through that action it would have no effect. Not entering a number at the command line does something different (in a way different) from specifying a number. Also the historical notes were updated to be more consistent and hopefully clearer than before. Since the author called the program yarng (see README.md for why this is) the Makefile now creates a symlink to it, rather than forcing users to go back and forth as the author gives example uses as well. The to use and try sections now also use yarng. Running make clobber (from make clean) will remove the symlink. The .gitignore file was updated: added yarng. The thanks-for-fixes.md file was updated slightly for the above changes, particularly the historical remarks, linking indeed to the historical remarks in the README.md file.
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@@ -1,3 +1,4 @@
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schweikh2
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schweikh2.orig
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prog.orig
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yarng
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@@ -38,7 +38,7 @@ include ../../var.mk
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# Common C compiler warnings to silence
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#
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CSILENCE= -Wno-trigraphs -Wno-sign-compare -Wno-string-plus-int -Wno-switch-bool
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CSILENCE= -Wno-trigraphs -Wno-sign-compare -Wno-string-plus-int -Wno-switch-bool -Wno-implicit-int
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# Common C compiler warning flags
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#
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@@ -132,15 +132,13 @@ all: data ${TARGET}
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${PROG}: ${PROG}.c
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${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
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${LN} -sf $@ yarng
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# alternative executable
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#
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alt: data ${ALT_TARGET}
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@${TRUE}
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${PROG}.alt: ${PROG}.alt.c
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${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
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# data files
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#
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data: ${DATA}
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@@ -157,7 +155,7 @@ everything: all alt
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###############
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#
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clean:
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${RM} -f ${OBJ} ${ALT_OBJ}
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${RM} -f ${OBJ} ${ALT_OBJ} yarng
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@-if [ -f indent.c ]; then \
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echo ${RM} -f indent.c; \
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${RM} -f indent.c; \
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+50
-45
@@ -1,9 +1,6 @@
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# Most Erratic Behavior
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Jens Schweikhardt
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DFN Network Operation Center
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Schlartaeckerweg 3 (Home address)
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D-71384 Weinstadt
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Germany
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<http://www.schweikhardt.net>
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@@ -18,34 +15,25 @@ make all
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```sh
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./schweikh2
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<some number>
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./yarng
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```
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or
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```sh
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./schweikh2 integer_number
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./yarng integer_number
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```
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## Try:
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```sh
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./schweikh2 5
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./schweikh2 5
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./yarng 5
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./schweikh2
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5
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./yarng
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# watch what it does
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```
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What is the difference here?
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What happens if you don't put in any number like the below?
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```sh
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./schweikh2
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<ENTER>
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```
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What is the difference there?
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## Judges' remarks:
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@@ -56,16 +44,14 @@ results different? Why?
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### Historical remarks:
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At the time of judging, some non-gcc compilers that were not fully ANSI standard
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did not compile this entry correctly.
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At the time this hint file was written, some gcc and egcs implementations ran
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into problem when building the original entry:
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did not compile this entry correctly. Also at that time, some gcc and egcs
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implementations ran into a problem when building the entry. Doing:
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```sh
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make schweikh2
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```
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This program often produced an error of the form:
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often produced an error of the form:
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```
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gcc -ansi schweikh2.alt.c -o schweikh2.alt
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@@ -78,26 +64,27 @@ as: Error: cca00NzV.s, line 58: malformed statement
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because the line:
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```c
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??=line 10 ONE(O(1,1,2,6,0,6))
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#line 10 ONE(O(1,1,2,6,0,6))
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```
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turns into the line:
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turned into the line:
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```c
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# 9 "01\012"
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```
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which causes gcc to give to the assembler the following two lines:
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(note, though, how that line is on line 11) which caused gcc to give to the
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assembler the following two lines:
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```asm
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.stabs "whey.c
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.stabs "schweikh2.c
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",132,0,0,Ltext1
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```
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and the lone `"` after the `#.file` line results in an assembler syntax error.
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and the lone `"` after the `#.file` line resulted in an assembly syntax error.
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In some cases one must compile using `gcc -g`:
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In some cases one had to compile using `gcc -g`:
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```sh
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make schweikh2 CFLAGS=-g
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@@ -105,25 +92,31 @@ make schweikh2 CFLAGS=-g
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to trigger this error.
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And with the proper text beyond the `\012`, it may be possible to have
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all kinds of fun adding `inline assembly` via `#line` directives. :-)
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For extra credit:
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With the proper text beyond the `\012`, it was even possible to have all kinds
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of fun adding inline assembly via `#line` directives. :-)
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#### For extra fun and credit:
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If your compiler had this bug, you could transform the line in the C program to
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inject assembly instructions in such a way that the program would compile.
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If you were able to do the above, you could try adding assembly instructions so
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that it will compile, execute and do something interesting.
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If you were able to do that, you could have tried adding assembly instructions
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so that it will compile, execute and do something interesting (or uninteresting,
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for that matter :-) ).
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If you succeeded in doing this (especially on FreeBSD, Linux or SPARC),
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If you succeeded in doing that (especially on FreeBSD, Linux or SunOS/Solaris),
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you could have emailed the author for a free pat on the back (and maybe you
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still can :-) ).
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NOTE: the author submitted the program as `yarng` so when trying the examples
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below change `yarng` to `./schweikh2`.
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Because of this bug, the code was changed to be instead:
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However in 2023 it was observed that it is gcc that has a problem with the
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compilation of the _modified_ program, giving an internal compiler error:
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```c
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#line 10 "01\015"
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```
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However in 2023 it was observed that _it is gcc_ (at least some versions?) that
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has a problem with the compilation of the _modified_ program, giving an internal
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compiler error:
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```
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:10:16: warning: type defaults to 'int' in declaration of 'zero' [-Wimplicit-int]
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@@ -132,8 +125,20 @@ compilation of the _modified_ program, giving an internal compiler error:
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:12:19: internal compiler error: invalid built-in macro "__FILE__"
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```
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so the string `"01\015"` was changed to `ONE(O(1,1,2,6,0,6))` and now it works
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with both clang and gcc.
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so the line:
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```c
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#line 10 "01\015"
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```
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was changed to:
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```c
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#line 10 ONE(O(1,1,2,6,0,6))
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```
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and now it works with both clang and gcc.
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## Author's remarks:
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@@ -170,9 +175,9 @@ $ ./yarng 5
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- Ever seen a 'do for ... while' loop?
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- I avoided `int` like the plague. Instead I used storage class specifiers
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(`register`, `auto`) to get implicit int. The Standard allows implicit int even in
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casts as you can see in `(void(*)(register))main`. Where implicit int is
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impossible, like in the `int main` declaration I have int split across two
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(`register`, `auto`) to get implicit `int`. The Standard allows implicit `int` even in
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casts as you can see in `(void(*)(register))main`. Where implicit `int` is
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impossible, like in the `int main` declaration I have `int` split across two
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lines. All indent programs I use insert space at the beginning of the
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continuation line and thereby introduce a syntax error.
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@@ -183,7 +188,7 @@ uttered "Works for me". Don't quote me on that!
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- Even if you know how the program works, you just can't predict the output.
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- Chained use of token pasting operators ## with shuffled arguments.
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- Chained use of token pasting operators `##` with shuffled arguments.
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- So you think you can't assign to `__LINE__` and `__FILE__`? Not so. The `#line`
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preprocessor directive does the trick. But saying `#line 10 "01\n"` is a little
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@@ -8,7 +8,7 @@ static volatile sig_atomic_t One;
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#define ONE(One) Zero(One)
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in??/
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t
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??=line 10 ONE(O(1,1,2,6,0,6))
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#line 10 ONE(O(1,1,2,6,0,6))
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main (register zero, char **ONE)
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%:
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<% switch (sizeof __FILE__ < zero) case 1: return One /= zero;
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+4
-1
@@ -948,7 +948,10 @@ Cody fixed the code to not trigger an internal compiler error in gcc:
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:12:19: internal compiler error: invalid built-in macro "__FILE__"
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```
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The string `"01\015"` had to be changed to `ONE(O(1,1,2,6,0,6))`.
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The string `"01\015"` had to be changed to `ONE(O(1,1,2,6,0,6))`. For an
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interesting historical explanation and further details and fun, see the
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[historical remarks](1998/schweikh2/README.md#historical-remarks) in the
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README.md.
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## [2000/anderson](2000/anderson/anderson.c) ([README.md](2000/anderson/README.md]))
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