Introduction

This is a straightforward configuration system for writing portable C systems with OpenBSD-compatible features and functions.

To use:

copy configure, compats.c, and tests.c into your source tree
have include Makefile.configure at the top of your Makefile
have #include "config.h" as the first inclusion in your sources
read over the documentation below in case you need to guard header inclusion
compile compats.o with your sources and link with it

It allows easy porting to Linux (glibc and musl), FreeBSD, NetBSD, Mac OS X, SunOS (Solaris 11), and OmniOS (illumos). Other systems may also be supported: please let us know if they are.

See versions.md for version information.

This framework was inspired by mandoc's configure script written by Ingo Schwarze.

Users and maintainers

Run ./configure prior to running make. The configure script will check for common features as noted in the test files, e.g., pledge(2), and also provide compatibility for other functions, e.g., strlcpy(3).

The ./configure script may be executed in a cross-compiling environment with the compiler and linker set appropriately.

If you have Makefile flags you'd like to set, set them when you invoke configure as key-value pairs on the command-line, e.g.,

./configure PREFIX=/opt

These are set in the generated Makefile.configure, which should be included by the source's Makefile. The following are recognised:

LDADD: -l libraries and flags usually used for linking binaries
LDLIBS: -l libraries and flags usually used for linking shared libraries (LIBADD is sometimes used for this)
LDFLAGS: -L linker flags used for linking
CPPFLAGS: C preprocessor flags used for compiling objects
DESTDIR: prefixed to all install directories during installation, but not otherwise affecting install directories
PREFIX: directory for default install directories (defaults to /usr/local)
MANDIR: install directory for manpages (defaults to PREFIX/man)
LIBDIR: install directory for libraries (defaults to PREFIX/lib)
BINDIR: install directory for binaries (defaults to PREFIX/bin)
SHAREDIR: install directory for shared files (defaults to PREFIX/share)
SBINDIR: install directory for system binaries (defaults to PREFIX/sbin)
INCLUDEDIR: install directory for header files (defaults to PREFIX/include)
LINKER_SONAME: linker command used to create shared libraries (defaults to -soname or -install_name)

Anything else is discarded and warned about.

If you want to use override the default AR, CC, or CFLAGS variables, specify them as environmental variables. (The results will be set either way in Makefile.configure.) For example:

CC=musl-gcc ./configure

The CC, LDFLAGS, CPPFLAGS, and CFLAGS are used when running the configuration tests themselves. If a default cc compiler is not found, oconfigure will test for clang and gcc before giving up.

For Linux users with libbsd installed, oconfigure can be instructed to use libbsd exclusively as follows:

CFLAGS=$(pkg-config --cflags libbsd-overlay) \
  ./configure LDFLAGS=$(pkg-config --libs libbsd-overlay)

For new versions of libbsd, this will pull in the library for all compatibility replacements instead of those within compats.c.

For shared library generation, a LINKER_SONAME variable (which may be overridden) is set in the generated Makefile.configure to assist in Mac OS X portability. Generating a shared library lib.so.0 from lib.c might look like:

cc -fPIC -o lib.o -c lib.c
cc -shared -o lib.so.0 -Wl,${LINKER_SONAME},lib.so.0 lib.o

The choice of -fPIC or -fpic is left for the user.

Developers

Using oconfigure requires some work within your sources to node compatibility areas, then some in your build environment:

#include "config.h" /* required inclusion */

#if HAVE_ERR /* sometimes err.h exists, sometimes not */
# include <err.h>
#endif
#include <stdio.h>
#include <unistd.h>

int main(void) {
#if HAVE_PLEDGE /* do we have pledge? */
	if (pledge("stdio", NULL) == -1)
		err(1, NULL);
#endif
	warnx("hello, world!"); /* compat provides this */
	return 0;
}

And then...

./configure
cc -o compats.o -c compats.c
cc -o main.o -c main.c
cc compats.o main.o

It's better to build this into your Makefile, as the output Makefile.configure will set compiler, compiler flags, installation utilities, and so on.

The following example also includes portable idioms for a depending library. It uses BSD make style. The compats.c is as given in oconfigure, and Makefile.configure and config.h are generated when running configure.

include Makefile.configure

LDADD_PKG != pkg-config --libs zlib || echo "-lz"
CFLAGS_PKG != pkg-config --cflags zlib || echo ""
LDADD += $(LDADD_PKG)
CFLAGS += $(CFLAGS_PKG)

main: main.o compats.o
	$(CC) -o $@ main.o compats.o $(LDFLAGS) $(LDADD)

install:
	mkdir -p $(DESTDIR)$(BINDIR)
	$(INSTALL_PROGRAM) main $(DESTDIR)$(BINDIR)

main.o compats.o: config.h

clean:
	rm -f main main.o compats.o

Features

What follows is a description of the features and facilities provided by the package when included into your sources.

arc4random(3)

Tests for the arc4random(3) functions in stdlib.h, defining HAVE_ARC4RANDOM with the result.

#if HAVE_ARC4RANDOM
# include <stdlib.h> /* arc4random, arc4random_buf... */
#endif

If not found, provides compatibility functions. The compatibility functions provide the same quality (via the same source) as OpenBSD, using the host's getentropy function for seed.

blowfish(3)

Tests for the original blf_enc(3) cipher functions including the raw block functions (not documented on OpenBSD, but still in the public API.

#if HAVE_BLOWFISH
# include <blf.h> /* blf_enc ... */
#endif

If not found, provides compatibility functions.

b64_ntop

This and its partner b64_pton are sometimes declared but not defined. The following will guard against that in your sources.

#if HAVE_B64_NTOP
# include <netinet/in.h>
# include <resolv.h>
#endif

Some systems (Linux in particular) with HAVE_B64_NTOP need -lresolv during linking. If so, set LDADD_B64_NTOP in Makefile.configure to -lresolv. Otherwise it is empty.

If the functions are not found, provides compatibility functions b64_ntop and b64_pton.

Since these functions are always poorly documented, the following demonstrates usage for b64_ntop, which translates src into an encoded NUL-terminated string dst and returns the string length or -1. The dstsz is the maximum size required for encoding.

srcsz = strlen(src);
dstsz = ((srcsz + 2) / 3 * 4) + 1;
dst = malloc(dstsz);
if (b64_ntop(src, srcsz, dst, dstsz) == -1)
	goto bad_size;

b64_pton reverses this situation from an encoded NUL-terminated string src into the decoded and NUL-terminated string dst (it's common not to need the NUL-terminator for the decoded string, which is meant to be binary). The dstsz is the maximum size required for decoding.

srcsz = strlen(src);
dstsz = srscsz / 4 * 3;
dst = malloc(dstsz + 1); /* NUL terminator */
if ((c = b64_pton(src, dst, dstsz)) == -1)
	goto bad_data;
dst[c] = '\0'; /* NUL termination */

Capsicum

Tests for FreeBSD's Capsicum subsystem, defining the HAVE_CAPSICUM variable with the result. Does not provide any compatibility.

#if HAVE_CAPSICUM
# include <sys/resource.h>
# include <sys/capsicum.h>
#endif

The guard is required for systems without these headers.

crypt(3)

On OpenBSD, passwords are managed primarily through crypt_newhash(3) and friends. However, the old crypt(3) function is still used in portable applications. Even though it's not very portable.

This tests for crypt(3), defining HAVE_CRYPT with the result.

On many systems with HAVE_CRYPT, you'll also need to add -lcrypt when you compile your system, else it will fail with undefined references.

The LDADD_CRYPT value provided in Makefile.configure will be set to -lcrypt if it's required. Otherwise it is empty.

crypt_newhash(3)

This tests for the crypt(3)-replacing functions crypt_newhash(3) and crypt_checkpass(3) functions, defining HAVE_CRYPT_NEWHASH with the result. Provides compatibility functions if not found.

Just as document, the portability functions only provide bcrypt functionality.

endian.h

On most operating systems (Linux, OpenBSD), endian.h provides the POSIX.1 endian functions, e.g., htole32(3), be32toh(3), etc. On FreeBSD, however, these are in sys/endian.h. Mac OS X and SunOS have their own functions in their own places.

The required invocation to use the endian functions is:

#if HAVE_ENDIAN_H
# include <endian.h>
#elif HAVE_SYS_ENDIAN_H
# include <sys/endian.h>
#elif HAVE_OSBYTEORDER_H
# include <libkern/OSByteOrder.h>
#elif HAVE_SYS_BYTEORDER_H
# include <sys/byteorder.h>
#endif

Compatibility for the Mac OS X and SunOS functions to the usual htole32 style is provided.

To make this easier, the COMPAT_ENDIAN_H is also defined:

#include COMPAT_ENDIAN_H

This will paste the appropriate location.

err.h

Tests for the err(3) functions, defining HAVE_ERR variable with the result. If not found, provides compatibility functions err, errx, errc, warn, warnx, warnc, and the variable-argument versions of each.

#if HAVE_ERR
# include <err.h>
#endif

The err.h header needs to be guarded to prevent systems using the compatibility functions for failing, as the header does not exist.

It's worth noting that glibc defines many of these functions, but misses the errc and warnc variations. oconfigure considers it all or nothing, so will not define HAVE_ERR in this case.

explicit_bzero(3)

Tests for explicit_bzero(3) in string.h, defining HAVE_EXPLICIT_BZERO with the result.

#include <string.h> /* explicit_bzero */

If not found, provides a compatibility function. The compatibility layer will use memset_s, if found. HAVE_EXPLICIT_BZERO shouldn't be directly used in most circumstances.

fts(3)

Tests for the fts_open(3) family of functions in fts.h, defining HAVE_FTS with the result. If not found, provides compatibility functions.

#if HAVE_FTS
# include <sys/types.h>
# include <fts.h> /* fts_open(3) et al. */
#endif

The fts.h header needs to be guarded to prevent systems using the compatibility functions for failing, as the header does not exist.

getprogname(3)

Tests for getprogname(3) in stdlib.h, defining HAVE_GETPROGNAME with the result. Provides a compatibility function if not found.

#include <stdlib.h> /* getprogname */

The compatibility function tries to use __progname, program_invocation_short_name, or getexecname(). If none of these interfaces may be found, it will emit a compile-time error. HAVE_GETPROGNAME shouldn't be directly used in most circumstances.

INFTIM

Tests for INFTIM in poll(2), defining HAVE_INFTIM with the result. Provides a compatibility value if not found.

#include <poll.h> /* INFTIM */

Since a compatibility function is provided, HAVE_INFTIM shouldn't be directly used in most circumstances.

landlock

Tests for Linux's landlock) LSM. Defines HAVE_LANDLOCK if found. Does not provide any compatibility.

This test does not mean that the module is enabled. You'll need to perform a run-time check for landlock_restrict_self's return value in your sources.

To actually use Landlock, you'll need to modify your system's LSM at boot time.

libsocket

On IllumOS-based distributions, all socket functions (bind(2), listen(2), socketpair(2), etc.) require linking to the -lsocket and -lnsl libraries.

If this is required, the LDADD_LIB_SOCKET variable in Makefile.configure will be set to the required libraries.

md5.h

Tests for the standalone md5(3) functions, defining HAVE_MD5 with the result.

If not found, provides a full complement of standalone (i.e., not needing any crypto libraries) MD5 hashing functions. These are MD5Init, MD5Update, MD5Pad, MD5Transform, MD5End, and MD5Final. The preprocessor macros MD5_BLOCK_LENGTH, MD5_DIGEST_LENGTH, and MD5_DIGEST_STRING_LENGTH are also defined.

These differ ever-so-slightly from the OpenBSD versions in that they use C99 types for greater portability, e.g., uint8_t instead of u_int8_t.

If using these functions, you'll want to guard an inclusion of the system-default. Otherwise a partial md5.h may conflict with results, or a missing md5.h may terminate compilation.

#if HAVE_MD5
# include <sys/types.h>
# include <md5.h>
#endif

On some systems (FreeBSD or those with Guillem Jover's libmd) with HAVE_MD5, you'll also need to add -lmd when you compile your system, else it will fail with undefined references.

The LDADD_MD5 value provided in Makefile.configure will be set to -lmd if it's required. Otherwise it is empty.

memmem(3)

Tests for memmem(3) in string.h, defining HAVE_MEMMEM with the result. Provides a compatibility function if not found.

#include <string.h> /* memmem */

Since a compatibility function is provided, HAVE_MEMMEM shouldn't be directly used in most circumstances.

memrchr(3)

Tests for memrchr(3) in string.h, defining HAVE_MEMRCHR with the result. Provides a compatibility function if not found.

#include <string.h> /* memrchr */

Since a compatibility function is provided, HAVE_MEMRCHR shouldn't be directly used in most circumstances.

minor(2)

major(2), minor(2), and makedev(2) all live in different places on different systems.

#if HAVE_SYS_MKDEV_H
# include <sys/types.h> /* dev_t */
# include <sys/mkdev.h> /* minor/major/makedev */
#elif HAVE_SYS_SYSMACROS_H
# include <sys/sysmacros.h> /* minor/major/makedev */
#else
# include <sys/types.h> /* minor/major/makedev */
#endif

This can be made much easier as follows, where COMPAT_MAJOR_MINOR_H is set to one of the above. sys/types.h may be included twice.

#include <sys/types.h>
#include COMPAT_MAJOR_MINOR_H

mkfifoat(2)

Tests for the mkfifoat(3) function, defining HAVE_MKFIFOAT with the result. Provides a compatibility function if not found.

This is not a direct replacement, as the function is not atomic: it internally gets a reference to the current directory, changes into the "at" directory, runs the function, then returns to the prior current.

Upon errors, it makes a best effort to restore the current working directory to what it was.

mknodat(2)

Tests for the mknodat(3) function, defining HAVE_MKNODAT with the result. Provides a compatibility function if not found.

This is not a direct replacement, as the function is not atomic: it internally gets a reference to the current directory, changes into the "at" directory, runs the function, then returns to the prior current.

Upon errors, it makes a best effort to restore the current working directory to what it was.

PATH_MAX

Tests for the PATH_MAX variable in limits.h, defining HAVE_PATH_MAX with the result. If not found, defines the PATH_MAX macro to be 4096.

#include <limits.h> /* PATH_MAX */

Since a compatibility value is provided, HAVE_PATH_MAX shouldn't be directly used in most circumstances.

pledge(2)

Test for pledge(2), defining HAVE_PLEDGE with the result. Does not provide any compatibility.

#include <unistd.h> /* pledge */

The HAVE_PLEDGE guard is not required except around the function invocation.

readpassphrase(3)

Tests for the readpassphrase(3) function, defining HAVE_READPASSPHRASE with the result. Provides a compatibility function if not found. The <readpassphrase.h> header inclusion needs to be guarded for systems that include it by default; otherwise, the definitions are provided in the generated config.h:

#if HAVE_READPASSPHRASE
# include <readpassphrase.h>
#endif

If using this function, makes sure you explicitly zero the passphrase buffer as described in readpassphrase(3).

reallocarray(3)

Tests for reallocarray(3) in stdlib.h, defining HAVE_REALLOCARRAY with the result. Provides a compatibility function if not found.

#include <stdlib.h> /* reallocarray */

Since a compatibility function is provided, HAVE_REALLOCARRAY shouldn't be directly used in most circumstances.

recallocarray(3)

Tests for recallocarray(3) in stdlib.h, defining HAVE_RECALLOCARRAY with the result. Provides a compatibility function if not found.

#include <stdlib.h> /* recallocarray */

Since a compatibility function is provided, HAVE_RECALLOCARRAY shouldn't be directly used in most circumstances.

sandbox_init(3)

Tests for sandbox_init(3), defining HAVE_SANDBOX_INIT with the result. Does not provide any compatibility.

scan_scaled(3), fmt_scaled(3)

Tests for OpenBSD's scan_scaled(3), defining HAVE_SCAN_SCALED if it was found. Provides a compatibility function if not found. If the function is not found, fmt_scaled(3) is also part of the compatibility package.

#if HAVE_SCAN_SCALED
# include <util.h>
#endif

If this is required, the LDADD_SCAN_SCALED variable in Makefile.configure will be set to the required library (-lutil).

seccomp-filter(3)

Tests for Linux's prctl(2) function, which is the gateway for seccomp(2). This defines several variables:

HAVE_SECCOMP_HEADER: Compile-time support exists for seccomp.
SECCOMP_AUDIT_ARCH: If HAVE_SECCOMP_HEADER is set, this is set to the architecture used for seccomp operations (e.g., AUDIT_ARCH_ARM). If this is not set and HAVE_SECCOMP_HEADER is set, seccomp is enabled in the kernel but the hardware architecture is not known by oconfigure. Please create an issue or pull request with your uname -m and hardware profile.
HAVE_SECCOMP_FILTER: Set if both HAVE_SECCOMP_HEADER and SECCOMP_AUDIT_ARCH are set.

Does not provide any compatibility.

This test does not mean that the sandboxing is enabled. You'll need to perform a run-time check for prctl's return value in your sources.

sha2.h

Tests for the standalone sha2(3) functions, defining HAVE_SHA2 with the result. This was previously provided as HAVE_SHA2_H, which still works as an alias for HAVE_SHA2.

If not found, provides a full complement of standalone SHA2 hashing functions. These are SHA256Init, SHA256Transform, SHA256Update, SHA256Pad, SHA256Final, SHA256End, SHA256File, SHA256FileChunk, and SHA256Data. The preprocessor macros SHA256_BLOCK_LENGTH, SHA256_DIGEST_LENGTH, and SHA256_DIGEST_STRING_LENGTH are also defined.

The SHA2 functions and macros are provided for SHA256, SHA384, and SHA512. So for example the SHA512Final function is also provided.

If using these functions, you'll want to guard an inclusion of the system-default. Otherwise a partial sha2.h may conflict with results, or a missing sha2.h may terminate compilation.

#if HAVE_SHA2
# include <sys/types.h>
# include <sha2.h>
#endif

On some systems (such as those with Guillem Jover's libmd) with HAVE_SHA2, you'll also need to add -lmd when you compile your system, else it will fail with undefined references.

The LDADD_SHA2 value provided in Makefile.configure will be set to -lmd if it's required. Otherwise it is empty.

SOCK_NONBLOCK

Tests for socketpair(2) in sys/socket.h supporting the SOCK_NONBLOCK mask as found on OpenBSD. Defines the HAVE_SOCK_NONBLOCK variable.

#if HAVE_SOCK_NONBLOCK
	socketpair(AF_UNIX, flags|SOCK_NONBLOCK, 0, fd);
#else
	socketpair(AF_UNIX, flags, 0, fd);
	fcntl(fd[0], F_SETFL, 
	      fcntl(fd[0], F_GETFL, 0)|O_NONBLOCK);
	fcntl(fd[1], F_SETFL, 
	      fcntl(fd[1], F_GETFL, 0)|O_NONBLOCK);
#endif

The guard is not required only around the variable usage, not header inclusion. However, the above example could have the fcntl.h header guarded by !HAVE_SOCK_NONBLOCK.

strlcat(3)

Tests for strlcat(3) in string.h, defining HAVE_STRLCAT with the result. Provides a compatibility function if not found.

#include <string.h> /* strlcat */

Since a compatibility function is provided, HAVE_STRLCAT shouldn't be directly used in most circumstances.

strlcpy(3)

Tests for strlcpy(3) in string.h, defining HAVE_STRLCPY with the result. Provides a compatibility function if not found.

#include <string.h> /* strlcpy */

Since a compatibility function is provided, HAVE_STRLCPY shouldn't be directly used in most circumstances.

strndup(3)

Tests for strndup(3) in string.h, defining HAVE_STRNDUP with the result. Provides a compatibility function if not found.

#include <string.h> /* strndup */

Since a compatibility function is provided, HAVE_STRNDUP shouldn't be directly used in most circumstances.

strnlen(3)

Tests for strnlen(3) in string.h, defining HAVE_STRNLEN with the result. Provides a compatibility function if not found.

#include <string.h> /* strnlen */

Since a compatibility function is provided, HAVE_STRNLEN shouldn't be directly used in most circumstances.

strtonum(3)

Tests for strtonum(3) in stdlib.h, defining HAVE_STRTONUM with the result. Provides a compatibility function if not found.

#include <stdlib.h> /* strtonum */

Since a compatibility value is provided, HAVE_STRTONUM shouldn't be directly used in most circumstances.

sys/queue.h

Tests for the queue(3) header, sys/queue.h. Defines HAVE_SYS_QUEUE if found and provides all of the queue macros if not. To use these macros, make sure to guard inclusion:

#if HAVE_SYS_QUEUE
# include <sys/queue.h>
#endif

This uses TAILQ_FOREACH_SAFE as a basis for determining whether the header exists and is well-formed. This is because glibc provides a skeleton sys/queue.h without this critical macro.

sys/tree.h

Tests for the tree(3) header, sys/tree.h. Defines HAVE_SYS_TREE if found and provides all of the tree macros if not. To use these macros, make sure to guard inclusion:

#if HAVE_SYS_TREE
# include <sys/tree.h>
#endif

systrace(4)

Tests for the deprecated systrace(4) interface. Defines HAVE_SYSTRACE if found. Does not provide any compatibility.

This function is never "found".

termios(4)

Tests for whether termios(4) exists, defining HAVE_TERMIOS with the result, specifically with the use case of testing terminal widths via ioctl(2) and TIOCGWINSZ (which must also exist). Does not provide any compaibility.

timingsafe_bcmp(3)

Tests for the timingsafe_bcmp(3) functions in string.h, defining HAVE_TIMINGSAFE_BCMP with the result.

#if HAVE_TIMINGSAFE_BCMP
# include <string.h> /* timingsafe_bcmp... */
#endif