From a8c5966ab27c7e487eae563550bef0013f8d9a63 Mon Sep 17 00:00:00 2001
From: Cody Boone Ferguson <53008573+xexyl@users.noreply.github.com>
Date: Mon, 10 Jul 2023 06:12:43 -0700
Subject: [PATCH] Elaborate on 2001/anonymous fix in thanks file

Mostly for educational value and because I documented a fair bit but it
was incomplete and I don't like to be incomplete.
---
 thanks-for-fixes.md | 44 +++++++++++++++++++++++++++++++-------------
 1 file changed, 31 insertions(+), 13 deletions(-)

diff --git a/thanks-for-fixes.md b/thanks-for-fixes.md
index 4ca714d2b..42c76b2ac 100644
--- a/thanks-for-fixes.md
+++ b/thanks-for-fixes.md
@@ -80,6 +80,11 @@ so that everyone can enjoy it with systems that are not VAX/PDP. We also refer y
 to the [FAQ](faq.md) as there are some winning entries that also let one enjoy
 it - with more to them of course!
 
+Cody also added the [gentab.c](1984/mullender/gentab.c) file, modified to
+compile with modern systems, which the author noted in their remarks which Cody
+also found.
+
+
 ## [1985/applin](1985/applin/applin.c) ([README.md](1985/applin/README.md]))
 
 Yusuke provided a patch to get this to not crash and Cody fixed this to
@@ -825,16 +830,40 @@ but according to the author's remarks it should be executed). He 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, it's a feature_ inherent in what it does!
 
-The following had to be done in order to get this to work:
+Below is what it took to fix.
 
 - `#include <sys/mman.h>` for `mmap()` and `munmap()`.
 - have `main()` call another function which is no longer a recursive function;
 this prevented `main()` from entering an infinite recursive loop.
 
-Without either of these it would crash and prevent modification of the 32-bit
+Without these it would crash and prevent modification of the 32-bit
 [ELF](https://en.wikipedia.org/wiki/Executable_and_Linkable_Format) (not elf :-) )
 binary. But again see [bugs.md](/bugs.md) here.
 
+These also had to be done:
+
+- when `open()`ing the file the file descriptor had to be saved so it could be
+closed prior to executing the program.
+- `munmap()` also had to be called prior to executing the program.
+
+Without those changes the program was not executed after modification which it
+was supposed to do, instead reporting text file busy error.
+
+Notice that the location of the calls to `munmap()` and `close()` followed by
+`execv()` _does matter_!
+
+To get this to compile with clang, `main()` had to change from:
+
+```c
+main (char *ck, char **k)
+```
+
+to:
+
+```c
+int main (int cka, char **k) { char *ck = (char *)cka; /* ... */ }
+```
+
 The following change was also made to be more portable, in case the constants
 `PROT_READ` and/or `PROT_WRITE` are not standardised:
 
@@ -842,17 +871,6 @@ 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).
 
-There was one other thing that had to be done though. Since the program used to
-recursively call (infinite recursion, seemingly) `main()` and since that cannot
-be done what had to be done instead is after the new function (`pain()` since it
-was a pain to fix :-) ) returns to first call `munmap()` and `close()` (else one
-would get text file busy error) and then the program can call `execv()` again
-like the function `pain()` (was in `main()`) did but with a slight change. See
-commit `2159caec4677e0f25ad704a74e04c8196fd6c343` for more details.
-
-Notice that the location of the calls to `munmap()` and `close()` followed by
-`execv()` _does matter_!
-
 NOTE: there might be educational value to see the progress of this fix; if you
 wish to see, try the following commands from the `2001/anonymous` directory: