Thinking that maybe the gcc version is too old I tried using instead CentOS gcc7 development environment (GCC) 7.3.1 20180303 (Red Hat 7.3.1-5) (which doesn't come out of the box). This was an educated guess as c99 is only partially supported in gcc-4.8.5. I have now successfully built:
libgpg-error-1.39
libassuan-2.5.3
gpgme-1.14.0
using gcc 7.3.1. All make check tests have passed.

The json problem can be overcome by changing the configure line to:

Actually I don't use systemd unit to start gpg-agent (creating that service file in systemd and make it start automatically) but I run it manually within the script. Also the script has selfcheck not to run multiple gpg-agent like below:

You used custom options which did not pick up the proper libksba. Install libksba correctly then try again. Please direct further questions to the mailing list and please build the latest version 2.2.23 and not an arbitrary old version.

@werner can you confirm if the environment I provided will work with OpenSSH support fully implemented?

We encountered the same issue today, and below is the debug messages. It works as expected once we downgraded to 2.2.21. We're on Arch Linux.

Version 2 is a bit too unspecific. Which version of what software are you using. Which OS?

Good catch. Thank you.

Hi,
I corrected all the accents. I created a PR here https://github.com/gpg/gpg4win/pull/3

Any ideas? Is there any other info needed that could help move this along?

There is a conflict between the systemd based launching of gpg-agent and gpg's own launching of the agent. Further systemd seems to remove the /run/user/UID directory which unlinks gpg-agent's socket. gpg-agent's self-check notices this after a minute and termintates itself.

I think that rG61aea64b3c17: scd: Fix the use case of verify_chv2 by CHECKPIN. fixes this issue.

I observed that the card reader's going erroneous state when I removed a card during its communication.
In this state, it never reports the card removal by the interrupt transfer.
I applied rG920f258eb601: scd: Internal CCID driver: More fix for SPR532. for this problem.

Great, thank you @gniibe.

Thanks for your report.

Update found out the answer for this mystery but I need to know why from you guys:

With all respect. Should I wait for a follow-up or I should consider this case as closed?

With 2.3 we add the keyboxd which uses sqlite (and thus indices) as database. This makes lookups much much faster and avoids problems with several processes accessing the pubring.kbx. If you want to try this you can do so with 2.3:

The patch rG684a52dffa8b: scd: Change handling of SPR532 card reader. makes me happier. It is more stable.

This is also what I found out with my tests with the libvirt usb: removing and redirecting back the device got it working again.

Testing more, I managed to encounter failure with physical usb.
Once in this failure mode, I need to remove the card reader from USB and reinsert again.
I need to figure out a sequence to avoid this situation and to reset the card reader correctly.

I tested with physical usb, did multiple operations with external events (insert/remove/etc. for card). I haven't seen any problem (if so, I were doing more fixes), so far.

That code in gnupg has not been touched in a very long time so this may be caused by some side effect.

Ok. Tried to test this with master, but failed. I got it compiled and installed, and it actually detected the first removal after reboot/suspend/reader attach/whatever reason, but after that when I inserted the card back, it didn't function anymore. I suppose you also tried that? I mean that's the use case, I suppose: to be able to remove/insert the card reliably all day long.

I am sorry, but I do not understand your request. Please give real commands as examples.
You known that you can always use --output FILENAME to force a certain file name?

Currently, yes. After some testing, I'll backport it to 2.2.