npth_t is untouched for Windows 64-bit.

assuan_sock_accept approach is taken in gnupg master.

gniibe/t6606 patches are all pushed into master.

Applied: rGb8c5d99406c9: gpg,agent,kbx,sm,scd,tpm2d,g13: Use assuan_control.

In T6606#173044, @gniibe wrote:

More care is needed to be perfect; There are places in GnuPG where assuan_sock_connect may be used before syscall clamp set up (after the first assuan_sock_bind failure).

Applied to master.

Applied the changes for libassuan T6487 into gniibe/t6606.

Pushed the change in gniibe/t6606 branch.

Another approach would be:

• Use assuan_sock_accept which has consistent API with gnupg_fd_t

On 64-bit Windows, the situation now is:

Use of FD2INT for the first argument of select is semantically not good. It's the number of file descriptor. When we use FD2INT here, the type is converted to 64-bit integer, then implicitly demoted to 32-bit integer. We need new macro, say, FD2NUM to convert FD into 32-bit integer.
<--- done in: rGea1935252e28: commond: Introduce FD2NUM to express conversion to number of fds.

Here is a test program for 64-bit Windows to see how cast works:

#include <stdint.h>
#include <stdio.h>

The case in check_special_filename is fixed. So, there is no cases in GnuPG where the value of out of range is silently converted to wrong value.

Remaining places are:

• common/sysutil.c debug output to format HANDLE --> T6597
• common/sysutil.c iobuf_get_fd and its use cases --> T6580
• agent, kbx, scdaemon, dirmngr: socket and FD2INT/INT2FD --> T6598

Except a case, all use cases of translate_sys2libc_fd_int is with a result of integer from command line argument.