C standard library¶
The C standard library is an integral part of any C program, and Zephyr provides two implementations for the application to choose from.
The first one, named “minimal libc” is part of the Zephyr code base and provides
the minimal subset of the standard C library required to meet the needs of
Zephyr and its subsystems and features, 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.
Its implementation can be found in lib/libc/minimal in the main zephyr
tree.
The second one is newlib, a complete C library implementation written for
embedded systems. Newlib is separate open source project and is not included in
source code form with Zephyr. Instead, the Install the Zephyr Software Development Kit (SDK) comes with a
precompiled library for each supported architecture (libc.a and
libm.a). Other 3rd-party toolchains, such as GNU ARM Embedded,
also bundle newlib as a precompiled library.
Newlib can be enabled by selecting the :kconfig:`CONFIG_NEWLIB_LIBC` in the
application configuration file. Part of the support for newlib is a set of
hooks available under lib/libc/newlib/libc-hooks.c which integrates
the C standard library with basic kernel services.
API Reference¶
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 are defined in the POSIX errno.h specification,
and others have been added to it from other sources.
A conscious effort is made in Zephyr to keep the values of system error numbers
consistent between the different implementations of the C standard library. The
version of errno.h that is in the main zephyr tree, errno.h, is
checked against newlib’s own list 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.
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group
system_errno System error numbers Error codes returned by functions. Includes a list of those defined by IEEE Std 1003.1-2017.
Defines
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errno¶
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EPERM¶ Not owner
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ENOENT¶ No such file or directory
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ESRCH¶ No such context
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EINTR¶ Interrupted system call
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EIO¶ I/O error
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ENXIO¶ No such device or address
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E2BIG¶ Arg list too long
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ENOEXEC¶ Exec format error
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EBADF¶ Bad file number
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ECHILD¶ No children
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EAGAIN¶ No more contexts
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ENOMEM¶ Not enough core
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EACCES¶ Permission denied
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EFAULT¶ Bad address
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ENOTBLK¶ Block device required
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EBUSY¶ Mount device busy
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EEXIST¶ File exists
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EXDEV¶ Cross-device link
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ENODEV¶ No such device
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ENOTDIR¶ Not a directory
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EISDIR¶ Is a directory
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EINVAL¶ Invalid argument
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ENFILE¶ File table overflow
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EMFILE¶ Too many open files
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ENOTTY¶ Not a typewriter
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ETXTBSY¶ Text file busy
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EFBIG¶ File too large
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ENOSPC¶ No space left on device
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ESPIPE¶ Illegal seek
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EROFS¶ Read-only file system
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EMLINK¶ Too many links
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EPIPE¶ Broken pipe
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EDOM¶ Argument too large
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ERANGE¶ Result too large
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ENOMSG¶ Unexpected message type
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EDEADLK¶ Resource deadlock avoided
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ENOLCK¶ No locks available
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ENOSTR¶ STREAMS device required
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ENODATA¶ Missing expected message data
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ETIME¶ STREAMS timeout occurred
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ENOSR¶ Insufficient memory
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EPROTO¶ Generic STREAMS error
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EBADMSG¶ Invalid STREAMS message
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ENOSYS¶ Function not implemented
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ENOTEMPTY¶ Directory not empty
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ENAMETOOLONG¶ File name too long
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ELOOP¶ Too many levels of symbolic links
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EOPNOTSUPP¶ Operation not supported on socket
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EPFNOSUPPORT¶ Protocol family not supported
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ECONNRESET¶ Connection reset by peer
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ENOBUFS¶ No buffer space available
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EAFNOSUPPORT¶ Addr family not supported
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EPROTOTYPE¶ Protocol wrong type for socket
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ENOTSOCK¶ Socket operation on non-socket
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ENOPROTOOPT¶ Protocol not available
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ESHUTDOWN¶ Can’t send after socket shutdown
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ECONNREFUSED¶ Connection refused
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EADDRINUSE¶ Address already in use
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ECONNABORTED¶ Software caused connection abort
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ENETUNREACH¶ Network is unreachable
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ENETDOWN¶ Network is down
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ETIMEDOUT¶ Connection timed out
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EHOSTDOWN¶ Host is down
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EHOSTUNREACH¶ No route to host
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EINPROGRESS¶ Operation now in progress
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EALREADY¶ Operation already in progress
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EDESTADDRREQ¶ Destination address required
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EMSGSIZE¶ Message size
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EPROTONOSUPPORT¶ Protocol not supported
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ESOCKTNOSUPPORT¶ Socket type not supported
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EADDRNOTAVAIL¶ Can’t assign requested address
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ENETRESET¶ Network dropped connection on reset
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EISCONN¶ Socket is already connected
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ENOTCONN¶ Socket is not connected
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ETOOMANYREFS¶ Too many references: can’t splice
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ENOTSUP¶ Unsupported value
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EILSEQ¶ Illegal byte sequence
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EOVERFLOW¶ Value overflow
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ECANCELED¶ Operation canceled
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EWOULDBLOCK¶ Operation would block
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