Help with "config.h file not found error" on Gnupg version 1.4.13

[Robert J. Hansen]

> First of all, thank you for taking your time to reply to this email. I
> tried it using the -l flag. The config file was found in the directory
> before that. Below is the command I executed.

I don't want to sound dismissive or discouraging, but you may want to 
consider whether you have the necessary C skills for the task you're 
undertaking.  Learning C development is difficult; learning 
cybersecurity is difficult; doing both at the same time borders on the 
impossible.

> I tried copying the header file mpi.h into the directory gnupg-1.4.13
> and compiling the mpi-pow.c program, now the error is like given
> below:

The easiest way to find all the directories you need to include is to 
take a look at the Autotools build script.  GnuPG was never meant to be 
compiled by hand, file-by-file.  Instead, there's an automated system to 
do it, and you can learn everything you need about how to build an 
individual file by studying this system.  Again, it's something you 
learn in the course of becoming a C developer.

> Is there anything wrong with the way I used the -l flag ? If so could
> anyone guide me in the right direction?

This is a compile-time (include file location) problem, not a link-time 
(library file location) problem.  Again: something discovered in the 
course of becoming a C developer.

Have you considered reaching out to the FLUSH+RELOAD paper authors, to 
see if they have a pre-built binary they might be willing to share with 
you?  It would be a heck of a lot faster than learning enough C to 
implement your own FLUSH+RELOAD on GnuPG.