Clarify gets()/fgets()/ARG_MAX in 1992/gson

By accident I stated that I changed this entry to not use gets() but
instead fgets(). This is unfortunately not true because of the way
gets() is used. I have now made it (I hope) a bit clearer. I also
pointed out that it's theoretically safe. Since it uses gets() which
comes from stdin ARG_MAX should be relevant. Thus I made the buffer size
ARG_MAX+1. But something I am not so clear on is whether or not ARG_MAX
is the entire command line or a single argument. Looking did not help
here as some say one thing and others say the other. Doing xargs
--show-limits and also checking the value of ARG_MAX suggests that it's
for the entire command but I don't know for sure of that. Nevertheless
it is safer than it was if not completely safe.
This commit is contained in:
Cody Boone Ferguson committed 2023-04-03 12:29:51 -07:00
1 parent 0791a31fc7
commit 89860e7b71
1 file changed
+13 -10
+13 -10
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@@ -14,16 +14,19 @@
./ag word word2 word3 < /path/to/dictionary
[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) fixed this entry to not
use gets(). Previously it had a buffer size of 256 which could easily overflow.
Now in this entry `gets()` is used in a more complicated way (first `m` is set
to `*++p` in a for loop where `p` is argv and then later `m` is set to point to
`h` which is of size 256) and trying to change it to use fgets() proved more a
problem. Since the input must come from the command line Cody changed the buffer
size to `ARG_MAX+1` which should be enough especially since the command expects
redirecting a dictionary file as part of the command line. This also makes it
possible for longer strings to be read (in case the `gets()` was not used in a
loop). Thank you Cody for your assistance!
[Cody Boone Ferguson](/winners.html#Cody_Boone_Ferguson) changed the buffer size
in such a way that gets() should be safe (theoretically) as it comes from the
command line. Ideally `fgets()` would be used but this is a more problematic.
Previously it had a buffer size of 256 which could easily overflow. Now in this
entry `gets()` is used in a more complicated way. First `m` is set to `*++p` in
a for loop where `p` is argv and then later `m` is set to point to `h` which is
of size 256. `gets()` is called as `m = gets(m)`) but trying to change it to use
fgets() proved more a problem. Since the input must come from the command line
Cody changed the buffer size to `ARG_MAX+1` which should be enough (again
theoretically) especially since the command expects redirecting a dictionary
file as part of the command line. This also makes it possible for longer strings
to be read (in case the `gets()` was not used in a loop). Thank you Cody for
your assistance!
## Judges' comment: