Reading from a Closed File Descriptor - linux

Question

I traced open, read, close and dup system calls in gimp-2.8.22 using strace, with the following command:
strace -eread,openat,open,close,dup,dup2 gimp
In gimp, I opened an image named babr.jpg. The trace shows that this image was opened (file descriptor is 14), read and closed. But, immediately after that, the same file descriptor (14 is not opened after the last close) is used for reading. How is it possible?
Here is the relevant portion of trace:
read(14, "\371\331\25\233M\311j\261b\271\332\240\33\315d\234\340y\236\217\323\206(\214\270x2\303S\212\252\254"..., 4096) = 4096
read(14, "t\260\265fv<\243.5A\324\17\221+\36\207\265&+rL\247\343\366\372\236\353\353'\226\27\27"..., 4096) = 318
close(14) = 0
openat(AT_FDCWD, "/home/ahmad/Pictures/babr.jpg", O_RDONLY) = 14
read(14, "\377\330\377\340\0\20JFIF\0\1\1\1\1,\1,\0\0\377\355(\212Photosho"..., 4096) = 4096
close(14) = 0
openat(AT_FDCWD, "/opt/gimp-2.8.22/lib/gimp/2.0/plug-ins/file-jpeg", O_RDONLY) = 19
read(19, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0P[\0\0\0\0\0\0"..., 4096) = 4096
close(19) = 0
close(20) = 0
read(19, "", 8) = 0
close(19) = 0
close(17) = 0
close(16) = 0
read(4, "\2\0\0\0\0\0\0\0", 16) = 8
Gtk-^[[1;32mMessage^[[0m: ^[[34m15:09:02.956^[[0m: Failed to load module "canberra-gtk-module"
read(14, "\0\0\0\5", 4) = 4
read(14, "\0\0\0\23", 4) = 4
read(14, "gimp-progress-init\0", 19) = 19
read(14, "\0\0\0\2", 4) = 4
I also checked this using Pin and found the same result.

Answer 1

The second file descriptor #14 is very likely a pipe between the plugin and Gimp (the handle being free has been reused). And you don't trace the creation of pipes.
From gimpplugin.c:
/* Open two pipes. (Bidirectional communication).
*/
if ((pipe (my_read) == -1) || (pipe (my_write) == -1))
{
gimp_message (plug_in->manager->gimp, NULL, GIMP_MESSAGE_ERROR,
"Unable to run plug-in \"%s\"\n(%s)\n\npipe() failed: %s",
gimp_object_get_name (plug_in),
gimp_file_get_utf8_name (plug_in->file),
g_strerror (errno));
return FALSE;
}