Fwd: odd behavior of length(), match() and field splitting with multi-byte characters

[Ed Morton]

Is there any more information I can provide for someone to be able to 
look into this bug?

     Ed.

On 7/6/2024 7:26 AM, Ed Morton wrote:
> I posted the below bug report to the GNU awk bugs mailing list, 
> https://lists.gnu.org/archive/html/bug-gawk/2024-07/msg00000.html, the 
> feedback there is that it's a cygwin or MSYS2 port issue, could you 
> please take a look? I'm also posting this at 
> https://github.com/msys2/mingw-packages/issues per the advice from the 
> GNU bug list.
>
> Regards,
>
>     Ed Morton.
>
> -------- Forwarded Message --------
> Subject: 	odd behavior of length(), match() and field splitting with 
> multi-byte characters
> Date: 	Mon, 1 Jul 2024 05:56:02 -0500
> From: 	Ed Morton
> To: 	bug-gawk@gnu.org <bug-gawk@gnu.org>
>
>
>
> Configuration Information [Automatically generated, do not change]:
> Machine: x86_64
> OS: cygwin
> Compiler: gcc
> Compilation CFLAGS: -ggdb -O2 -pipe -Wall -Werror=format-security 
> -Wp,-D_FORTIFY_SOURCE=2 -fstack-protector-strong 
> --param=ssp-buffer-size=4 
> -fdebug-prefix-map=/cygdrive/d/a/scallywag/gawk/gawk-5.3.0-1.x86_64/build=/usr/src/debug/gawk-5.3.0-1 
> -fdebug-prefix-map=/cygdrive/d/a/scallywag/gawk/gawk-5.3.0-1.x86_64/src/gawk-5.3.0=/usr/src/debug/gawk-5.3.0-1 
> -DNDEBUG
> uname output: CYGWIN_NT-10.0-22631 TournaMart_2023 3.5.3-1.x86_64 
> 2024-04-03 17:25 UTC x86_64 Cygwin
> Machine Type: x86_64-pc-cygwin
>
> Gawk Version: 5.3.0
>
> Attestation 1:
>         I have read 
> https://www.gnu.org/software/gawk/manual/html_node/Bugs.html.
>         Yes
>
> Attestation 2:
>         I have not modified the sources before building gawk.
>         True
>
> Description:
>         gawk is reporting odd lengths and matches of strings
>         when multi-byte characters are involved.
>
> Repeat-By:
>         Someone on StackOverflow asked about a couple of issues they 
> saw that, so far at least, no-one there can explain and seem to just 
> be bugs.
>
>         1) 
> https://stackoverflow.com/questions/78676444/conditional-replacement-of-arbitrarily-large-strings-that-occur-at-arbitrary-dis#comment138715434_78676444 
> and 
> https://stackoverflow.com/questions/78676444/conditional-replacement-of-arbitrarily-large-strings-that-occur-at-arbitrary-dis#comment138720207_78676444:
>
>         If we output 4 multi-byte characters as 10 bytes using:
>
>             $ echo '61F09F948DF09F948E62' | xxd -r -p > file1
>             $
>
>         and run the following gawk command on it we get the output shown:
>
>             $ LC_ALL=en_US.utf8 gawk '{print(length($0))}' file1
>             6
>             $
>
>         i.e. 6 instead of 4. If we run
>
>             $ printf 'F0989A9F' | xxd -r -p | LC_ALL=en_US.utf8 awk -F 
> '' '{print NF, length(); for (i=1; i<=NF; i++) print $i}' | cat -A
>             2 2$
>             M-pM-^XM-^Z$
>             M-^_$
>             $
>
>         it shows that what is intended to be single a 4-byte character 
> is being treated as 2 characters, one 3 bytes and the other 1 byte.
>
>         2) 
> https://stackoverflow.com/questions/78690533/why-does-the-match-function-not-work-in-this-particular-situation
>
>         If we create some input using:
>
>             $ echo 
> '3C6469763E3C6469763E5F3C2F6469763E5F3C68313E6162636465665F3C2F68313E5F3C2F6469763E3C6469763EF09F93853C2F6469763E0A' 
> | xxd -r -p > file2
>
>         and then run this on it we get the expected output shown::
>
>             $ LC_ALL=en_US.utf8 gawk 
> '{match($0,/^.*_<h1>(.*)_<\/h1>.*$/,a); print a[1]}' file2
>             abcdef
>             $
>
>         but if we add the `IGNORECASE` flag we get a blank line output:
>
>             $  LC_ALL=en_US.utf8 gawk -vIGNORECASE=1 
> '{match($0,/^.*_<h1>(.*)_<\/h1>.*$/,a); print a[1]}' file2
>
>             $
>
>         unless we also remove the end of string delimiter, `$`, from 
> the end of the regexp:
>
>             $ LC_ALL=en_US.utf8 gawk -vIGNORECASE=1 
> '{match($0,/^.*_<h1>(.*)_<\/h1>.*/,a); print a[1]}' file2
>             abcdef
>             $
>