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

Merge pull request #1049 from xexyl/1998-schweikh2-fixes

Browse Source
This commit is contained in:
Landon Curt Noll authored and GitHub committed 2023-10-14 05:15:07 -07:00
2 parents 1cf18e6869 e1f617bb15
commit 18a6aecb53
5 files changed
+59 -52
Download Patch File Download Diff File Expand all files Collapse all files

No files matched your search

1998/schweikh2/.gitignore
+1
View File
@@ -1,3 +1,4 @@
schweikh2
schweikh2.orig
prog.orig
yarng
1998/schweikh2/Makefile
+3 -5
View File
@@ -38,7 +38,7 @@ include ../../var.mk
# Common C compiler warnings to silence
#
CSILENCE= -Wno-trigraphs -Wno-sign-compare -Wno-string-plus-int -Wno-switch-bool
CSILENCE= -Wno-trigraphs -Wno-sign-compare -Wno-string-plus-int -Wno-switch-bool -Wno-implicit-int
# Common C compiler warning flags
#
@@ -132,15 +132,13 @@ all: data ${TARGET}
${PROG}: ${PROG}.c
${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
${LN} -sf $@ yarng
# alternative executable
#
alt: data ${ALT_TARGET}
@${TRUE}
${PROG}.alt: ${PROG}.alt.c
${CC} ${CFLAGS} $< -o $@ ${LDFLAGS}
# data files
#
data: ${DATA}
@@ -157,7 +155,7 @@ everything: all alt
###############
#
clean:
${RM} -f ${OBJ} ${ALT_OBJ}
${RM} -f ${OBJ} ${ALT_OBJ} yarng
@-if [ -f indent.c ]; then \
echo ${RM} -f indent.c; \
${RM} -f indent.c; \
1998/schweikh2/README.md
+50 -45
View File
@@ -1,9 +1,6 @@
# Most Erratic Behavior
Jens Schweikhardt
DFN Network Operation Center
Schlartaeckerweg 3 (Home address)
D-71384 Weinstadt
Germany
<http://www.schweikhardt.net>
@@ -18,34 +15,25 @@ make all
```sh
./schweikh2
<some number>
./yarng
```
or
```sh
./schweikh2 integer_number
./yarng integer_number
```
## Try:
```sh
./schweikh2 5
./schweikh2 5
./yarng 5
./schweikh2
5
./yarng
# watch what it does
```
What is the difference here?
What happens if you don't put in any number like the below?
```sh
./schweikh2
<ENTER>
```
What is the difference there?
## Judges' remarks:
@@ -56,16 +44,14 @@ results different? Why?
### Historical remarks:
At the time of judging, some non-gcc compilers that were not fully ANSI standard
did not compile this entry correctly.
At the time this hint file was written, some gcc and egcs implementations ran
into problem when building the original entry:
did not compile this entry correctly. Also at that time, some gcc and egcs
implementations ran into a problem when building the entry. Doing:
```sh
make schweikh2
```
This program often produced an error of the form:
often produced an error of the form:
```
gcc -ansi schweikh2.alt.c -o schweikh2.alt
@@ -78,26 +64,27 @@ as: Error: cca00NzV.s, line 58: malformed statement
because the line:
```c
??=line 10 ONE(O(1,1,2,6,0,6))
#line 10 ONE(O(1,1,2,6,0,6))
```
turns into the line:
turned into the line:
```c
# 9 "01\012"
```
which causes gcc to give to the assembler the following two lines:
(note, though, how that line is on line 11) which caused gcc to give to the
assembler the following two lines:
```asm
.stabs "whey.c
.stabs "schweikh2.c
",132,0,0,Ltext1
```
and the lone `"` after the `#.file` line results in an assembler syntax error.
and the lone `"` after the `#.file` line resulted in an assembly syntax error.
In some cases one must compile using `gcc -g`:
In some cases one had to compile using `gcc -g`:
```sh
make schweikh2 CFLAGS=-g
@@ -105,25 +92,31 @@ make schweikh2 CFLAGS=-g
to trigger this error.
And with the proper text beyond the `\012`, it may be possible to have
all kinds of fun adding `inline assembly` via `#line` directives. :-)
For extra credit:
With the proper text beyond the `\012`, it was even possible to have all kinds
of fun adding inline assembly via `#line` directives. :-)
#### For extra fun and credit:
If your compiler had this bug, you could transform the line in the C program to
inject assembly instructions in such a way that the program would compile.
If you were able to do the above, you could try adding assembly instructions so
that it will compile, execute and do something interesting.
If you were able to do that, you could have tried adding assembly instructions
so that it will compile, execute and do something interesting (or uninteresting,
for that matter :-) ).
If you succeeded in doing this (especially on FreeBSD, Linux or SPARC),
If you succeeded in doing that (especially on FreeBSD, Linux or SunOS/Solaris),
you could have emailed the author for a free pat on the back (and maybe you
still can :-) ).
NOTE: the author submitted the program as `yarng` so when trying the examples
below change `yarng` to `./schweikh2`.
Because of this bug, the code was changed to be instead:
However in 2023 it was observed that it is gcc that has a problem with the
compilation of the _modified_ program, giving an internal compiler error:
```c
#line 10 "01\015"
```
However in 2023 it was observed that _it is gcc_ (at least some versions?) that
has a problem with the compilation of the _modified_ program, giving an internal
compiler error:
```
:10:16: warning: type defaults to 'int' in declaration of 'zero' [-Wimplicit-int]
@@ -132,8 +125,20 @@ compilation of the _modified_ program, giving an internal compiler error:
:12:19: internal compiler error: invalid built-in macro "__FILE__"
```
so the string `"01\015"` was changed to `ONE(O(1,1,2,6,0,6))` and now it works
with both clang and gcc.
so the line:
```c
#line 10 "01\015"
```
was changed to:
```c
#line 10 ONE(O(1,1,2,6,0,6))
```
and now it works with both clang and gcc.
## Author's remarks:
@@ -170,9 +175,9 @@ $ ./yarng 5
- Ever seen a 'do for ... while' loop?
- I avoided `int` like the plague. Instead I used storage class specifiers
(`register`, `auto`) to get implicit int. The Standard allows implicit int even in
casts as you can see in `(void(*)(register))main`. Where implicit int is
impossible, like in the `int main` declaration I have int split across two
(`register`, `auto`) to get implicit `int`. The Standard allows implicit `int` even in
casts as you can see in `(void(*)(register))main`. Where implicit `int` is
impossible, like in the `int main` declaration I have `int` split across two
lines. All indent programs I use insert space at the beginning of the
continuation line and thereby introduce a syntax error.
@@ -183,7 +188,7 @@ uttered "Works for me". Don't quote me on that!
- Even if you know how the program works, you just can't predict the output.
- Chained use of token pasting operators ## with shuffled arguments.
- Chained use of token pasting operators `##` with shuffled arguments.
- So you think you can't assign to `__LINE__` and `__FILE__`? Not so. The `#line`
preprocessor directive does the trick. But saying `#line 10 "01\n"` is a little
1998/schweikh2/schweikh2.c
+1 -1
View File
@@ -8,7 +8,7 @@ static volatile sig_atomic_t One;
#define ONE(One) Zero(One)
in??/
t
??=line 10 ONE(O(1,1,2,6,0,6))
#line 10 ONE(O(1,1,2,6,0,6))
main (register zero, char **ONE)
%:
<% switch (sizeof __FILE__ < zero) case 1: return One /= zero;
thanks-for-fixes.md
+4 -1
View File
@@ -948,7 +948,10 @@ Cody fixed the code to not trigger an internal compiler error in gcc:
:12:19: internal compiler error: invalid built-in macro "__FILE__"
```
The string `"01\015"` had to be changed to `ONE(O(1,1,2,6,0,6))`.
The string `"01\015"` had to be changed to `ONE(O(1,1,2,6,0,6))`. For an
interesting historical explanation and further details and fun, see the
[historical remarks](1998/schweikh2/README.md#historical-remarks) in the
README.md.
## [2000/anderson](2000/anderson/anderson.c) ([README.md](2000/anderson/README.md]))