libcurl's binary interface
ABI - Application Binary Interface
+----------------------------------
- First, allow me to define the word for this context: ABI describes the
- low-level interface between an application program and a library. Calling
- conventions, function arguments, return values, struct sizes/defines and
- more.
+ "ABI" describes the low-level interface between an application program and a
+ library. Calling conventions, function arguments, return values, struct
+ sizes/defines and more.
- For a longer description, see
- http://en.wikipedia.org/wiki/Application_binary_interface
+ [Wikipedia has a longer description](http://en.wikipedia.org/wiki/Application_binary_interface)
Upgrades
+--------
In the vast majority of all cases, a typical libcurl upgrade does not break
the ABI at all. Your application can remain using libcurl just as before,
it now is defined to work.
Version Numbers
+---------------
In libcurl land, you really can't tell by the libcurl version number if that
libcurl is binary compatible or not with another libcurl version.
Soname Bumps
+------------
Whenever there are changes done to the library that will cause an ABI
breakage, that may require your application to get attention or possibly be
During the first seven years of libcurl releases, there have only been four
ABI breakages.
+ We are determined to bump the SONAME as rarely as possible. Ideally, we
+ never do it again.
+
Downgrades
+----------
Going to an older libcurl version from one you're currently using can be a
tricky thing. Mostly we add features and options to newer libcurls as that
soname, and then your application may need to adapt to the modified ABI.
History
+-------
The previous major library soname number bumps (breaking backwards
compatibility) have happened the following times: