All changes in gniibe/t7855 are pushed into master.

Fixed in master: rGae431b04370f: w32:common: Take care of possible race on startup under Windows.

This issue should be fixed in 2.6, too.

Pushed the change to gnupg master: rG61ff3759e827: common,dirmngr:w32: Fix for semi-hosted environment.

In libgpg-error, I pushed thread-safe version : rE0313b660f8bd: w32: Don't convert slash->backslash when it's under Wine.
I'm going to push similar code to gnupg master.

Lastly, pushed a change into gniibe/t7855 branch.
rGf861b2a33f96: gpg,gpgsm: Fix thinko for FP closing under no lock.

I pushed further changes into gniibe/t7855 branch.
rG2fe62809014e: gpg,gpgsm: Serialize write access to keybox/keyring to protect.

I'm fixing this issue under T7855. So, I move this ticket as a child of T7855.

For remaining changes in 2.2, I pushed changes into gniibe/t7855 branch.
rGbd65b06b74c2: gpg,gpgsm: Don't lock recursively when KEEP_LOCK is enabled.
rG423fd047da87: kbx,gpg,gpgsm: Add FP-close method for keydb to close before unlock.
rG966258ac5f99: gpgsm: Fix delete and store certificate locking glitches.

I pushed changes into gniibe/t7855 for compressing the keybox.
rG8cc2a0e0ffee: gpg: Minor clean up for keydb_lock API.
rGe4d3c3aa2220: kbx,gpg,gpgsm: Introduce keybox_compress_when_no_other_users.
rG3e441d5b299f: kbx,gpg,gpgsm: More changes for compressing the keybox.

Then, we need to integrate following commits of 2.2 into gniibe/t7855 branch:
rG43fe9073aa81: gpg,gpgsm: Tweak the locking of the pubring.kbx
rG8491aca73cff: gpg: Revert the always locking introduced with 43fe9073aa
rGad4a5117ab1c: gpgsm: Properly release the lock when compressing a pubring.
rG7962eca3a023: gpgsm: Change delete and store certificate locking glitches.
rG22f9c4a3b3c1: gpg: Release lock after close also in the compress code path.

I created gniibe/t7855 branch for this issue.
To start with, I forward-port/cherry-pick 2.2 commits to the branch:
rG39430d9f78dc: build,common,g13,sm,tools: Require GpgRT 1.56.
rGe71aca2a628d: common: New function gnupg_remove_ext.
rGe38c5f7d5873: w32:common: Take care of possible race on startup under Windows.
rG7bfd37e305c0: common,w32: Always use share mode readwrite for the keybox.

@timegrid Thank you for your confirmation.

Sorry for my late review. I should have reviewed earlier.

I understand that this is for 2.6.

Here are places where I found problems.

Fixed in 1.56.

Fixed in 1.3.2.

Reading the commit log message in rG6dc3846d7819: sm: Support creation of EdDSA certificates.
I created a file to keygen.

Key-Type: ECDSA
Key-Length: 1024
Key-Grip: 0286DCA85E771F64AB9FD9C89717369524D55471
Key-Usage: sign,encrypt
Hash-Algo: sha384
Serial: random
Name-DN: CN=dummy test nistp384

I updated the branch.

I think that modifying gnupg_remove is a bit risky because it's used in many places.
I'd rather introduce new function for Windows; gnupg_w32_delete_file for this particular purpose.
Factoring out wait_when_sharing_violation function from gnupg_rename_file.

Here is a possible fix:

This is current work of mine:

I can't find any causes of slowness in keyboxd initialization. I think that there is a situation where it simply takes time on Windows.

@ametzler1 Thank you.

test -a is not a POSIX construct, I intentionally avoided it.

@ametzler1 Thank you for your report.
I modified a bit (not using && between two test but using -a for a single test command), and pushed the change:
rP121494245f49: build: Allow build with fltk 1.4.

@m.eik Could you please enable debug option for gpg-agent and get the log output for the crash?

I fixed the problem (which I identified above) in gniibe/t7759 branch. There might be other causes/problems for the particular symptom, so, I don't know the fix resolves the symptom or not, though. Anyhow, I believe that this is an improvement.

Thank you for the report.

Similar situation could happen with gpgsm + gpg-agent, when gpg-agent is invoked by gpgsm.
(1) No gpg-agent.
(2) In gpgme, by engine-gpgsm, gpgsm is invoked with --logger.
(3) In gpgsm_keylist, it makes sure gpg-agent is available by GETINFO agent-check, using gpgsm_assuan_simple_command.
(4) In the server side, it tries to connect gpg-agent, invokes gpg-agent, and connect to the agent again.
(5) On Windows, it may takes time to invoke gpg-agent. And it may try to connect multiple times. Each trial may generate debug messages.
(6) When it takes too much time, the debug messages are too much. It may fill the pipe.
(7) And it blocks at log_string in my_libassuan_log_handler.
(8) ... it hangs.

Hypothetical scenario (gpgsm --server + dirmngr):
(0) It may hang when much debug messages are generated by libassuan to the pipe of --logger (diag_cb).
(1) In gpgme, by engine-gpgsm, gpgsm is invoked with --logger.
(2) If it's the case of standard gpgme interactions which uses gpgsm_io_event, no problem. Because the data on diag_cb is consumed well.
(3) In case of gpgsm_encrypt (or other commands), it uses gpgsm_assuan_simple_command which does not consume the data on diag_cb pipe at all.
(4) In particular, in set_recipients, gpgsm_assuan_simple_command is called by the number of recipients times.
(5) IIUC, in the server side, to handle RECIPIENT command, dirmngr is used by the call chain of:

• cmd_recipient
• gpgsm_add_to_certlist
• gpgsm_validate_chain...
• gpgsm_dirmngr_isvalid

(6) In gpgsm_dirmngr_isvalid function, libassuan is used as client side, it generates debug messages.
(7) When there are many recipients, the debug message may be big enough to fill the pipe.
(8) When pipe is filled, it blocks at log_string in my_libassuan_log_handler, waiting the data in pipe is consumed.
(9) ... it hangs.