CYGWIN supports "/dev/fd" for listing the set of file descriptors open in a process.

[carlo-bramini]

Bug report

Bug description:

While inspecting the code for finding the causes of the issues of my build for CYGWIN, I found this piece of code:

cpython/Modules/_posixsubprocess.c

Lines 66 to 70 in 5c3deca

	#if defined(__FreeBSD__) || (defined(__APPLE__) && defined(__MACH__)) || defined(__DragonFly__)
	# define FD_DIR "/dev/fd"
	#else
	# define FD_DIR "/proc/self/fd"
	#endif

CYGWIN supports /dev/fd and not /dev/self/fd as you can see here:

so a tiny fix is needed for adding __CYGWIN__ to the list of platforms to support the rigth entry with the set of file descriptors open in a process.

CPython versions tested on:

CPython main branch

Operating systems tested on:

Windows

Linked PRs

• gh-148575: Use the right entry to read the set of file descriptors on CYGWIN #148576