Merge pull request #393 from xexyl/1990-theorem

1990/theorem/Makefile

@@ -115,7 +115,7 @@ PROG= ${ENTRY}
 #
 OBJ= ${PROG}.o
 DATA=
-TARGET= ${PROG} sorter fibonacci
+TARGET= ${PROG} sorter fibonacci theorem_bkp
 #
 ALT_OBJ=
 ALT_TARGET=
@@ -133,7 +133,6 @@ all: data ${TARGET}
 	supernova deep_magic magic charon pluto
 
 ${PROG}: ${PROG}.c
-	@echo "NOTE: this entry will segfault on no arg specified."
 	${CC} ${CFLAGS} $< -o $@ ${LIBS}
 
 sorter.c: ${PROG} ${PROG}.c
@@ -148,6 +147,12 @@ fibonacci.c: sorter ${PROG}.c
 fibonacci: fibonacci.c
 	${CC} ${CFLAGS} fibonacci.c -o $@
 
+theorem_bkp: sorter theorem_bkp.c
+	${CC} ${CFLAGS} theorem_bkp.c -o $@
+
+theorem_bkp.c:
+	-./sorter -r 0 0 0 0 < sorter.c > theorem_bkp.c
+
 # alternative executable
 #
 alt: data ${ALT_TARGET}

1990/theorem/README.md

@@ -18,14 +18,14 @@ impacted the usability of this program including some segfaults under modern
 systems (and possibly in some cases earlier systems) with this entry.
 Originally we noted that the 4 trailing args '0 0 0 0' were required on systems
 that dump core when NULL is dereferenced but this problem showed itself in
-modern systems even with the 4 '0 0 0 0'. He also fixed the code so that the
+modern systems even with the 4 '0 0 0 0'. He also fixed a segfault if not enough
-generated `fibonacci.c` actually works; before it just printed `0` over and over
+args are specified and fixed the code so that the generated `fibonacci.c`
-again (since it did not work anyway a segfault prevention was added here). He
+actually works; before it just printed `0` over and over again (since it did not
-also some array addressing (some of which might not be strictly necessary but as
+work anyway a segfault prevention was added here). He also some array addressing
-he was testing the `fibonacci.c` bug he ended up changing it anyway). Finally he
+(some of which might not be strictly necessary but as he was testing the
-changed this program to use `fgets()` not `gets()` to make it safer and to
+`fibonacci.c` bug he ended up changing it anyway). Finally he changed this
-prevent a warning about `gets()` at linking or runtime. Thank you Cody for your
+program to use `fgets()` not `gets()` to make it safer and to prevent a warning
-assistance!
+about `gets()` at linking or runtime. Thank you Cody for your assistance!
 
 [Yusuke Endoh](/winners.html#Yusuke_Endoh) pointed out that `atof` nowadays
 needs `#include <stdlib.h>` which was used in order to get this to work
@@ -46,7 +46,6 @@ where:
 	h - step size
 	y1 - initial value  (y(x1) == y1)
 
-NOTE: this entry will segfault on no arg specified.
 
 ## Try:
 
@@ -54,6 +53,11 @@ NOTE: this entry will segfault on no arg specified.
 ./theorem y 0 1 0.1 1
 ```
 
+### Known bug with `fibonacci.c` and `theorem_bkp.c`:
+
+If the two args added up equals 0 the program will enter an infinite loop,
+printing 0 over and over again. Cody fixed another condition where this happens
+but this has not been fixed. See [bugs.md](/bugs.md) for more details.
 
 ## Judges' comments:
 

1990/theorem/theorem.c

@@ -23,7 +23,9 @@ C
 w(g,R,u)float*g,u;char R;
 /**/{int b,f;if(A>2){A=atoi(a[1]);b=atoi(a[2]);while((f=A+b)<15000){printf("%d\n",f);A=b;b=f;}}}
 main(A,a)int A;char*a[];
-o o
+o
+o
+if (a[1]==NULL||a[2]==NULL||a[3]==NULL||a[4]==NULL||a[5]==NULL) return 1;
 if(!strcmp(*++a,"-r"))S();
 D=atof(*++a);
 T=atof(*++a);

bugs.md

@@ -27,6 +27,16 @@ format is consistent and clean.
 
 THANK YOU!
 
+## To the winning authors:
+
+If you're the author of an entry that has been fixed and you find it against
+your liking **PLEASE** let us know and we'll be happy to undo any fixes even if
+it takes away some instructional value or even usability. _In this case we're
+**VERY SORRY_** about it: it's a fine line, we know, and we tried to use careful
+judgement but invariably some might have been the wrong decision. Thank you for
+understanding!
+
+
 ### ON **ALL** FIXES / IMPROVEMENTS / CHANGES
 
 Make **ABSOLUTE CERTAIN** that you test the entry _BEFORE_ **AND** _AFTER_ your
@@ -122,6 +132,11 @@ when formatting code.
 Entries with this status have one or more bugs that need to be fixed. Are you
 able to fix it? We welcome your help!
 
+An important point to note is that there is a very fine line when fixing bugs
+where it might sometimes border on tampering with the program. And after all,
+these are not meant to be maintainable or even good programming style! Use
+careful judgement when fixing bugs please!
+
 ## STATUS: possible bug (possibly depending on system) - please help test and if necessary fix
 
 Entries with this status might or might not have a bug possibly depending on the
@@ -239,19 +254,19 @@ An example where a crash is not a bug: [2019/endoh](2019/endoh/endoh.c) is
 supposed to crash. There are others that are also supposed to crash or that are
 known to segfault but are considered features.
 
-As of 07 April 2023 the definition changed where just because an entry segfaults
+As of 10 April 2023 the definition changed for a second time (the first time was
-because of (for example) invalid input does not mean it's a bug that should be
+07 April 2023). If something is noted by the author as a known bug or limitation
-fixed. [Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) fixed some of the
+it need not be fixed unless it impacts the usability of the program or removes
-entries but he felt this is tampering with the entries (that after all are not
+instructional value. An example where a crash undocumented needn't be fixed is
-meant to be maintainable or even good programming style!); thus the definition
+[1984/laman](1984/laman/laman.c).  On the other hand the fixes made by [Cody
-of this status was changed and the 'fixes' were rolled back. There might be some
+Boone Ferguson](/winners.html#Cody_Boone_Ferguson) in
-exceptions where the entry did not actually work or compile under some systems;
+[1990/theorem](1990/theorem/theorem.c) were useful.
-in this case depending on how complicated the fix is it might not have been
-rolled back.
 
-We challenge you to fix them for educational/instructional value and/or
+Nonetheless we challenge you to fix these entries for educational/instructional
-enjoyment but we kindly request that you **DO NOT** submit a pull request! If
+value and/or enjoyment but we kindly request that you **DO NOT** submit a pull
-you can't figure it out you're invited to look at the git diffs if you wish.
+request! If you can't figure it out you're invited to look at the git diffs,
+where there are some (some were fixed earlier on but rolled back due the fix
+feeling like tampering).
 
 NOTE: in the case of `gets()` we've fixed some to avoid the warning of the
 compiler, linker or even during runtime, depending on the system. In [one
@@ -470,11 +485,47 @@ so it should stay with this note.
 
 
 ## [1990/theorem](1990/theorem/theorem.c) ([README.md](1990/theorem/README.md))
-## STATUS: INABIAF - please **DO NOT** fix
+## STATUS: known bug - please help us fix
 
-[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) fixed some segfaults in
+[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) fixed many bugs that
-this entry that prevented it from working. However if not enough args are
+prevented this from working properly (including segfaults) but one bug known to
-specified this program will crash.  This should NOT be fixed.
+exist remains: if `theorem_bkp` or `fibonacci` is passed two zeros the program
+will enter an infinite loop, printing 0 over and over again (another condition
+where this occurred was fixed).
+
+Cody provides some hints here:
+
+0. The function in `theorem.c` that matters is `w` (see below for definition).
+1. However adding checks for the value being > 0 does not work due to the way the
+code is generated. See below.
+
+`w()` looks like this:
+
+```c
+w(g,R,u)float*g,u;char R;
+/**/{int b,f;if(A>2){A=atoi(a[1]);b=atoi(a[2]);while((f=A+b)<15000){printf("%d\n",f);A=b;b=f;}}}
+```
+
+But as far as point 1 above changing it to be:
+
+```c
+/**/{int b,f;if(A>2){A=atoi(a[1]);b=atoi(a[2]);while(f!=0&&(f=A+b)<15000){printf("%d\n",f);A=b;b=f;}}}
+```
+
+and similar (like checking `>0`, doing a `do..while`, doing an `if` before the
+while etc.) cause compilation errors.
+
+Can you fix this? We welcome your help!
+
+BTW: one of the important fixes for `fibonacci` to work is:
+
+```diff
+-/**/{int b,f;A=atoi(++a);b=atoi(++a);while((f=A+b)<15000){printf("%d\n",f);A=b;b=f;}}
++/**/{int b,f;if(A>2){A=atoi(a[1]);b=atoi(a[2]);while((f=A+b)<15000){printf("%d\n",f);A=b;b=f;}}}
+```
+
+Observe the check for the number of args and the calls to `atoi()` have been
+changed a bit too.
 
 
 ## [1990/westley](1990/westley/westley.c) ([README.md](1990/westley/README.md))