Minimal libc
The most basic C library, named “minimal libc”, is part of the Zephyr codebase and provides the minimal subset of the standard C library required to meet the needs of Zephyr and its subsystems, primarily in the areas of string manipulation and display.
It is very low footprint and is suitable for projects that do not rely on less frequently used portions of the ISO C standard library. It can also be used with a number of different toolchains.
The minimal libc implementation can be found in lib/libc/minimal in the
main Zephyr tree.
Functions
The minimal libc implements the minimal subset of the ISO/IEC 9899:2011 standard C library functions required to meet the needs of the Zephyr kernel, as defined by the Coding Guidelines Rule A.4.
Formatted Output
The minimal libc does not implement its own formatted output processor;
instead, it maps the C standard formatted output functions such as printf
and sprintf to the cbprintf() function, which is Zephyr’s own
C99-compatible formatted output implementation.
For more details, refer to the Formatted Output OS service documentation.
Dynamic Memory Management
The minimal libc uses the malloc api family implementation provided by the common C library, which itself is built upon the kernel memory heap API.
Error numbers
Error numbers are used throughout Zephyr APIs to signal error conditions as
return values from functions. They are typically returned as the negative value
of the integer literals defined in this section, and are defined in the
errno.h header file.
A subset of the error numbers defined in the POSIX errno.h specification and other de-facto standard sources have been added to the minimal libc.
A conscious effort is made in Zephyr to keep the values of the minimal libc
error numbers consistent with the different implementations of the C standard
libraries supported by Zephyr. The minimal libc errno.h is checked
against that of the Newlib to ensure that the error
numbers are kept aligned.
Below is a list of the error number definitions. For the actual numeric values please refer to errno.h.
- group system_errno
System error numbers Error codes returned by functions.
Includes a list of those defined by IEEE Std 1003.1-2017.
Defines
-
errno
-
EPERM
Not owner.
-
ENOENT
No such file or directory.
-
ESRCH
No such context.
-
EINTR
Interrupted system call.
-
EIO
I/O error.
-
ENXIO
No such device or address.
-
E2BIG
Arg list too long.
-
ENOEXEC
Exec format error.
-
EBADF
Bad file number.
-
ECHILD
No children.
-
EAGAIN
No more contexts.
-
ENOMEM
Not enough core.
-
EACCES
Permission denied.
-
EFAULT
Bad address.
-
ENOTBLK
Block device required.
-
EBUSY
Mount device busy.
-
EEXIST
File exists.
-
EXDEV
Cross-device link.
-
ENODEV
No such device.
-
ENOTDIR
Not a directory.
-
EISDIR
Is a directory.
-
EINVAL
Invalid argument.
-
ENFILE
File table overflow.
-
EMFILE
Too many open files.
-
ENOTTY
Not a typewriter.
-
ETXTBSY
Text file busy.
-
EFBIG
File too large.
-
ENOSPC
No space left on device.
-
ESPIPE
Illegal seek.
-
EROFS
Read-only file system.
-
EMLINK
Too many links.
-
EPIPE
Broken pipe.
-
EDOM
Argument too large.
-
ERANGE
Result too large.
-
ENOMSG
Unexpected message type.
-
EDEADLK
Resource deadlock avoided.
-
ENOLCK
No locks available.
-
ENOSTR
STREAMS device required.
-
ENODATA
Missing expected message data.
-
ETIME
STREAMS timeout occurred.
-
ENOSR
Insufficient memory.
-
EPROTO
Generic STREAMS error.
-
EBADMSG
Invalid STREAMS message.
-
ENOSYS
Function not implemented.
-
ENOTEMPTY
Directory not empty.
-
ENAMETOOLONG
File name too long.
-
ELOOP
Too many levels of symbolic links.
-
EOPNOTSUPP
Operation not supported on socket.
-
EPFNOSUPPORT
Protocol family not supported.
-
ECONNRESET
Connection reset by peer.
-
ENOBUFS
No buffer space available.
-
EAFNOSUPPORT
Addr family not supported.
-
EPROTOTYPE
Protocol wrong type for socket.
-
ENOTSOCK
Socket operation on non-socket.
-
ENOPROTOOPT
Protocol not available.
-
ESHUTDOWN
Can’t send after socket shutdown.
-
ECONNREFUSED
Connection refused.
-
EADDRINUSE
Address already in use.
-
ECONNABORTED
Software caused connection abort.
-
ENETUNREACH
Network is unreachable.
-
ENETDOWN
Network is down.
-
ETIMEDOUT
Connection timed out.
-
EHOSTDOWN
Host is down.
-
EHOSTUNREACH
No route to host.
-
EINPROGRESS
Operation now in progress.
-
EALREADY
Operation already in progress.
-
EDESTADDRREQ
Destination address required.
-
EMSGSIZE
Message size.
-
EPROTONOSUPPORT
Protocol not supported.
-
ESOCKTNOSUPPORT
Socket type not supported.
-
EADDRNOTAVAIL
Can’t assign requested address.
-
ENETRESET
Network dropped connection on reset.
-
EISCONN
Socket is already connected.
-
ENOTCONN
Socket is not connected.
-
ETOOMANYREFS
Too many references: can’t splice.
-
ENOTSUP
Unsupported value.
-
EILSEQ
Illegal byte sequence.
-
EOVERFLOW
Value overflow.
-
ECANCELED
Operation canceled.
-
EWOULDBLOCK
Operation would block.
-
errno