5 \___|\___/|_| \_\_____|
7 libcurl's binary interface
9 ABI - Application Binary Interface
11 First, allow me to define the word for this context: ABI describes the
12 low-level interface between an application program and a library. Calling
13 conventions, function arguments, return values, struct sizes/defines and
16 For a longer descricption, see
17 http://en.wikipedia.org/wiki/Application_binary_interface
21 In the vast majority of all cases, a typical libcurl upgrade does not break
22 the ABI at all. Your application can remain using libcurl just as before,
23 only with less bugs and possibly with added new features. You need to read
24 the release notes, and if they mention an ABI break/soname bump, you may
25 have to verify that your application still builds fine and uses libcurl as
26 it now is defined to work.
30 In libcurl land, you really can't tell by the libcurl version number if that
31 libcurl is binary compatible or not with another libcurl version.
35 Whenever there are changes done to the library that will cause an ABI
36 breakage, that may require your application to get attention or possibly be
37 changed to adhere to new things, we will bump the soname. Then the library
38 will get a different output name and thus can in fact be installed in
39 parallell with an older installed lib (on most systems). Thus, old
40 applications built against the previous ABI version will remain working and
41 using the older lib, while newer applications build and use the newer one.
43 During the first seven years of libcurl releases, there have only been four
48 Going to an older libcurl version from one you're currently using can be a
49 tricky thing. Mostly we add features and options to newer libcurls as that
50 won't break ABI or hamper existing applications. This has the implication
51 that going backwards may get you in a situation where you pick a libcurl
52 that doesn't support the options your application needs. Or possibly you
53 even downgrade so far so you cross an ABI break border and thus a different
54 soname, and then your application may need to adapt to the modified ABI.