#include bug

[Tomasz Borowczyk]

Hello.
I tried to use GNU Autogen to generate some code for my embedded system 
project and it works nice unless I try to modularize definitions files 
and use the #include directive. Here is the example with three files:

params.def file:
ext_param1 = "test ext_param1 successful";

inc.def file:
Autogen definitions inc;
#include params.def
param1 = "param1 test successful";

inc.tpl file:
[+ AutoGen5 template txt +]
[+param1+]
[+ext_param1+]

The three files above are in the same directory. I have autogen 5.18.16 
installed on Ubuntu 22.04.2 with apt install autogen command. When I run :
autogen inc.def
I get:
WARNING: fserr 2 (No such file or directory) performing 'search for' on 
inc.def
and the output file inc.txt has the following contents:
param1 test successful

When I run the same command on Cygwin on Windows 8.1 I get:
fserr 0: cannot read params.def: No error
Aborted (core dumped)
and no output file.

When I replace the #include directive with:
#shell cat params.def #endshell
I get:
Missing #endshell after '#shell' in inc.def on line 3
(strange because this is in line 2 in inc.def file.

Am I doing something wrong? Is it a bug? I tried to download Autogen 
5.19.98 and compile from source and after I run:
config/bootstrap
aclocal
autoconf
./configure
make
I get a lot of errors that look like:
./sys/select.h:744:5: error: #if with no expression

This is all what I have tried.

Best regards,
Tomasz