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From: Keith Thompson <kst-u@mib.org>
Newsgroups: comp.lang.c
Subject: Re: What are the odds? (a continuation of One works ...)
Date: Wed, 06 Nov 2019 19:26:28 -0800
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DFS <nospam@dfs.com> writes:
[...]
> char charset[62]
> ="abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
> int charsetLen = strlen(charset);
> printf("%d \n",charsetLen);
> 62

That still has undefined behavior.  It appears to "work" only because,
most likely, there just happens to be a null byte in memory immediately
after charset.

I just compiled and ran your on my system.  I got 62 with gcc and clang,
and 65 with tcc.  There is not necessarily any particular reason for
this, and it could just as easily produce different results tomorrow.

> char charset[63] =
> "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789";
> int charsetLen = strlen(charset);
> printf("%d \n",charsetLen);
> 62

That's well defined, but as I mentioned elsethread your (incorrect)
strlen call is the only thing that relies on charset containing a valid
string.

If you define charset using [] you can get its size using sizeof.

>> When you tested the code, did you not notice extraneous lines of 
>> output after the line for "9"?
>
> Not seeing that.  Compiled and ran on tcc/Windows and gcc (MSYS2) and 
> there are no extraneous lines of output after the output for 9.

That's one of thep problems with undefined behavior: it can evade
testing.

[...]

-- 
Keith Thompson (The_Other_Keith) kst-u@mib.org  <http://www.ghoti.net/~kst>
Working, but not speaking, for Philips Healthcare
void Void(void) { Void(); } /* The recursive call of the void */