The manpage to errno tells the following story:
The <errno.h> header file defines the integer variable errno, which is
set by system calls and some library functions in the event of an error
to indicate what went wrong. Its value is significant only when the
return value of the call indicated an error (i.e., -1 from most system
calls; -1 or NULL from most library functions); a function that
succeeds is allowed to change errno.
Valid error numbers are all nonzero; errno is never set to zero by any
system call or library function.
These file systems are provided on-demand by loading a shared library
when the fstab node is traversed. By convention this library is named
after the file system it provides. For example a file system that
provides a 'random' file system node is called 'vfs_random.lib.so'. It
is still possible to give the the node another name in the vfs. The
following code snippts illustrates this matter:
! [...]
! <config>
! <libc>
! <vfs>
! <dir name="dev"> <jitterentropy name="random"/> </dir>
! </vfs>
! </libc>
! </config>
! [...]
Here the jitterentropy file system, implemented in
'vfs_jitterentropy.lib.so' provides a file system node named 'random'
in the 'dev' directory. When traversing the vfs section the libc will
try to load 'vfs_jitterentropy.lib.so' but programs may access the
file system only via '/dev/random'.
Fixes#1240.
This patch changes the top-level directory layout as a preparatory
step for improving the tools for managing 3rd-party source codes.
The rationale is described in the issue referenced below.
Issue #1082
Christian Helmuth
Alexander Boettcher
Josef Söntgen
Norman Feske