The library provides a set of compatibility macros and functions commonly found on BSD-based systems. Its purpose is to make those available on non-BSD based systems to ease portability. The library can be used in an overlay mode, which is the preferred way, so that the code is portable and requires no modification to the original BSD code. This can be done easily with the library named Or by adding the system-specific include directory with the suffix to the list of system include paths. With this could be In addition the pre-processor variable needs to be defined. The includes in this case should be the usual system ones, such as The other way to use the library is to use the namespaced headers, this is less portable as it makes using mandatory and it will not work on BSD-based systems, and requires modifying original BSD code. This can be done with the library named The includes in this case should be namespaced with such as The package also provides a static library that can be used to inject automatic constructors into a program so that the function gets invoked automatically at startup time. This can be done with the library named The following are the headers provided by that extend the standard system headers. They can work in normal or overlay modes, for the former they need to be prefixed with The following is a specific convenience header, that includes some of the extended headers. It only works in non-overlay mode. Some functions have different prototypes depending on the BSD where they originated from, and these various implementations provided are selectable at build-time. This is the list of functions that provide multiple implementations: added and but unfortunately made it incompatible with the existing one in and Freedesktop's libbsd (the former having existed for over ten years). Despite this incompatibility being reported during development (see http://gnats.netbsd.org/44977) they still shipped it. Even more unfortunately and later MacOS picked up this incompatible implementation. Provide both implementations and default for now to the historical one to avoid breakage, but we will switch to the one in a later release, which is internally consistent with the other functions and is now more widespread. Define to switch to the Define to keep using the one. Some functions have been deprecated, they will emit warnings at compile time and possibly while being linked at run-time. This might be due to the functions not being portable at all to other systems, making the package not buildable there; not portable in a correct or non-buggy way; or because there are better more portable replacements now. This is the list of currently deprecated macros and functions: Unportable, requires assistance from the stdio layer. An implementation has to choose between leaking buffers or being reentrant for a limited amount of streams (this implementation chose the latter with a limit of 32). Use instead, which is available in many systems and required by Unportable, requires assistance from the stdio layer. An implementation has to choose between leaking buffers or being reentrant for a limited amount of streams (this implementation chose the latter with a limit of 32). Use instead, which is available in many systems and required by and Unportable, requires assistance from the stdio layer or some hook framework. On GNU systems the function can be used. Otherwise the code needs to be prepared for neither of these functions being available. Some functions have been superseded by implementations in other system libraries, and might disappear on the next SONAME bump, assuming those other implementation have widespread deployment, or the implementations are present in all major for example. The set of MD5 digest functions are now proxies for the implementations provided by the companion library, so it is advised to switch to use that directly instead. This function is provided by 2.25. This function is provided by 2.26. The project started in the Debian GNU/kFreeBSD port as a way to ease porting code from FreeBSD to the GNU-based system. Pretty early on it was generalized and a project created on FreeDesktop.org for other distributions and projects to use. It is now distributed as part of most non-BSD distributions.