5 \___|\___/|_| \_\_____|
7 libcurl's binary interface
9 ABI - Application Binary Interface
10 ----------------------------------
12 "ABI" describes the low-level interface between an application program and a
13 library. Calling conventions, function arguments, return values, struct
14 sizes/defines and more.
16 [Wikipedia has a longer description](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.
31 In libcurl land, you really can't tell by the libcurl version number if that
32 libcurl is binary compatible or not with another libcurl version.
37 Whenever there are changes done to the library that will cause an ABI
38 breakage, that may require your application to get attention or possibly be
39 changed to adhere to new things, we will bump the soname. Then the library
40 will get a different output name and thus can in fact be installed in
41 parallel with an older installed lib (on most systems). Thus, old
42 applications built against the previous ABI version will remain working and
43 using the older lib, while newer applications build and use the newer one.
45 During the first seven years of libcurl releases, there have only been four
48 We are determined to bump the SONAME as rarely as possible. Ideally, we
54 Going to an older libcurl version from one you're currently using can be a
55 tricky thing. Mostly we add features and options to newer libcurls as that
56 won't break ABI or hamper existing applications. This has the implication
57 that going backwards may get you in a situation where you pick a libcurl
58 that doesn't support the options your application needs. Or possibly you
59 even downgrade so far so you cross an ABI break border and thus a different
60 soname, and then your application may need to adapt to the modified ABI.
65 The previous major library soname number bumps (breaking backwards
66 compatibility) have happened the following times:
68 0 - libcurl 7.1, August 2000
70 1 - libcurl 7.5 December 2000
72 2 - libcurl 7.7 March 2001
74 3 - libcurl 7.12.0 June 2004
76 4 - libcurl 7.16.0 October 2006