Track down required changes in 2001/anonymous

In order to know what had to change exactly I tested this out (though it's possible I forgot to initially document changes and so I did not test everything) and I have documented it in the README.md. The required changes: - remove infinite recursion from main(): move the body of main() to another function. - add #include <sys/mman.h> for mmap(). Without either this did not work. I also changed (in case of non-standardised constants) '3' in the call to mmap() to be PROT_READ|PROT_WRITE but this appears to not be strictly required. I added the script try.me.sh which has more commands than the previous try section to show how it works and what changes etc. Updated .gitignore as the above script creates some. Make make all attempt to compile anonymous.ten.c: it's an important part of the program though it can work on other 32-bit ELF binaries. Update bugs.md explaining why this won't work with macOS.
2023-05-02 03:11:18 -07:00
1 parent ffc50a98a5
commit 9990fe2abd
@@ -1,2 +1,6 @@
 anonymous
 anonymous.ten
+ten.bak.od
+ten.bak.txt
+ten.od
+ten.txt
@@ -117,7 +117,7 @@ PROG= ${ENTRY}
 #
 OBJ= ${PROG}.o
 DATA= 
-TARGET= ${PROG}
+TARGET= ${PROG} ${PROG}.ten
 #
 ALT_OBJ=
 ALT_TARGET=
@@ -135,7 +135,6 @@ all: data ${TARGET}
 	supernova deep_magic magic charon pluto

 ${PROG}: ${PROG}.c
-	@echo "NOTE: this entry seems to no longer work."
 	magic='${CC} ${CFLAGS}'; \
 	X='-DA(X)=#X'; \
 	warning='-Dprocessor'; \
@@ -144,12 +143,17 @@ ${PROG}: ${PROG}.c


 ${PROG}.ten: ${PROG}.ten.c
-	@echo "NOTE: this program must be compiled as 32-bit to use with the entry itself."
-	@echo "if you want to use it where this is not possible e.g. with a Mac try, say to"
+	@echo "WARNING: ${PROG}.ten.c must be compiled as 32-bit to use with the entry itself;"
+	@echo "this is because the program works on 32-bit binaries. If you cannot use -m32 this"
+	@echo "will NOT work!"
+	@echo
+	@echo "If you want to use it where this is not possible e.g. with a Mac, say to"
 	@echo "use by itself, try:"
 	@echo
 	@echo "	    ${CC} $< -o $@"
 	@echo
+	@echo "but running ${PROG} on the resulting binary will crash."
+	@echo
 	${CC} ${CFLAGS} -m32 $< -o $@ ${LIBS}

 # alternative executable
@@ -181,6 +185,7 @@ clean:

 clobber: clean
 	${RM} -f ${TARGET} ${ALT_TARGET}
+	${RM} -f anonymous.ten.bak ten.od ten.od.bak ten.txt ten.bak.txt
 	@-if [ -e sandwich ]; then \
 	    ${RM} -f sandwich; \
 	    echo 'ate sandwich'; \
@@ -15,25 +15,53 @@ make
 ./anonymous x86_program
 ```

-NOTE: [Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) fixed both the
+[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) fixed both the
 supplementary program and the program itself, both of which segfaulted. He
-managed to do this with linux but it will not work with macOS (see below why);
-this is not a bug but a feature inherent in what it does. He said this took
-serious debugging and skill (shameless self promotion but it's true :-) ) and we
-thank him _very much_!
+managed to do this with linux but it will not work with macOS (see
+[bugs.md](/bugs.md) for why this is); this is not a bug but a feature inherent
+in what it does. He said this took serious debugging and skill (shameless self
+promotion but it's true :-) ) and we thank him _very much_! But what needed to
+be changed? Although it took a fair bit of debugging it turns out all that
+needed to be changed was:

-Why does this not work on macOS? Because Apple has made it very hard to compile
-32-bit programs. It's even harder with the Apple silicon chip. Thus this will
-have to remain for linux only. BSD was not tested. 
+- `#include <sys/mman.h>` for `mmap()`.
+- have `main()` call another function which is the recursive function; this
+prevented `main()` from entering an infinite loop.

-WARNING: this will somewhat destroy files that it is used on. See the author's
-warning about this.
+Without either of these it would crash and prevent modification of the 32-bit
+[ELF](https://en.wikipedia.org/wiki/Executable_and_Linkable_Format) (not elf :-)
+) binary. The following change was also made to be more portable, in case the
+constants `PROT_READ` and/or `PROT_WRITE` are not standardised:
+
+Change `3` in the call to `mmap()` to be `PROT_READ|PROT_WRITE`: just in case
+`PROT_READ|PROT_WRITE` does not equal 3 (though it seems to be equal in both
+macOS and linux).
+
+NOTE: there might be educational value to see the progress of this fix; if you
+wish to see, try:
+
+```sh
+git diff d2a42f42e8f477f29e9d5ed09ce2bb349eaf7397..93aa8d79f208dcccc3c5a2370a727b5cf64e9c53 anonymous.c
+git diff 93aa8d79f208dcccc3c5a2370a727b5cf64e9c53..c48629017117379a52b1a512ef8f2593ca9569c8 anonymous.c
+git diff c48629017117379a52b1a512ef8f2593ca9569c8..efdee208a2bc650256637b9357ddfd0de82d2f41 anonymous.c
+git diff efdee208a2bc650256637b9357ddfd0de82d2f41..e9a3f77ea3b209e63ac3f9c06bb84ad86e5ea706 anonymous.c
+```
+
+### WARNING on note from the author
+
+The author suggested that this will somewhat destroy the binaries this touches
+but Cody did not observe this. It does indeed modify the files as the script
+below will show you (though not all files are modified: can you figure out why
+that is?) but Cody did not notice any problems in using them. Perhaps it's
+something he's not aware of. If you follow the try commands below you will
+notice that although the binaries do differ it's not many differences. See the
+author's warning about this.

 ### INABIAF - it's not a bug it's a feature! :-)

 This entry will not work on 64-bit binaries! The program itself can be compiled
-as 64-bit but the files it processes must be 32-bit binaries. Not doing this
-will likely cause a crash or cause your computer [halt and catch
+as 64-bit but the files it processes must be 32-bit ELF binaries. Not doing this
+will likely cause a crash or cause your computer to [halt and catch
 fire](https://en.wikipedia.org/wiki/Halt_and_Catch_Fire_(computing)! :-)

 This entry will also very likely crash if no arg is specified. It might do
@@ -42,8 +70,7 @@ something funny if you run it on itself as well but see below :-)
 ## Try:

 ```sh
-make anonymous.ten
-./anonymous anonymous.ten
+./try.me.sh
 ```

 What happens if the x86 program has already been modified by this program?
@@ -53,7 +80,6 @@ you recompile it okay? What if you run it on `anonymous` itself? Can you run the
 program successfully after it without recompiling?


-
 ## Judges' remarks:

 Is emulation the sincerest form of flattery?  This small program does
@@ -0,0 +1,24 @@
+#!/usr/bin/env bash
+
+make clobber
+make all 2>/dev/null
+echo "$ cp anonymous.ten anonymous.ten.bak" 1>2
+cp anonymous.ten anonymous.ten.bak
+echo "$ ./anonymous anonymous.ten" 1>&2
+./anonymous anonymous.ten
+echo "$ ./anonymous.ten" 1>&2
+./anonymous.ten
+echo "$ diff -s anonymous.ten anonymous.ten.bak" 1>&2
+diff -s anonymous.ten anonymous.ten.bak
+echo "$ od anonymous.ten > ten.od" 1>&2
+od anonymous.ten > ten.od
+echo "$ od anonymous.ten.bak > ten.bak.od" 1>&2
+od anonymous.ten.bak > ten.bak.od
+echo "$ diff ten.bak.od ten.od" 1>&2
+diff ten.bak.od ten.od
+echo "$ ./anonymous.ten > ten.txt" 1>&2
+./anonymous.ten > ten.txt
+echo "$ ./anonymous.ten.bak > ten.bak.txt" 1>&2
+./anonymous.ten.bak > ten.bak.txt
+echo "$ diff -s ten.txt ten.bak.txt" 1>&2
+diff -s ten.txt ten.bak.txt
@@ -195,6 +195,8 @@ Please help us by writing alternative code!

 ## STATUS: main() function args not allowed - please help us fix

+At this time all of these have been fixed but the below is what it's all about.
+
 Entries with this status have a problem in that the args to main() are not of a
 specific type due to this being allowed in earlier C. Some compilers like clang
 have a deficiency where they do not allow this so these entries do not work with
@@ -1051,6 +1053,24 @@ fire](https://en.wikipedia.org/wiki/Halt_and_Catch_Fire_(computing))! :-) ).

 # 2001

+## [2001/anonymous](2001/anonymous/anonymous.c) ([README.md](2001/anonymous/README.md))
+## STATUS: INABIAF - please **DO NOT** fix
+
+[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) fixed this so that it
+works in modern systems but he notes that the program
+[anonymous.ten.c](2001/anonymous/anonymous.ten.c) **MUST** be compiled as a
+32-bit ELF binary! This because the program acts on 32-bit ELF binaries. If you
+cannot use `-m32` on this file the program **will** almost certainly crash but
+in no case will it work properly.
+
+This means that for macOS it will not work. Why will this not work in macOS?
+Because Apple saw to it to make it very hard to compile 32-bit binaries (thanks
+Apple for ruining some IOCCC entries! :-) :-( ). This appears to be even harder
+with the Apple silicon chip. Thus this entry will not work with macOS unless you
+have an older, out of date version.
+
+Other BSD Unices were not tested.
+
 ## [2001/bellard](2001/bellard/bellard.c) ([README.md](2001/bellard/README.md))
 ## STATUS: doesn't work with some platforms - please help us fix