1 _ _ ____ _ 2 ___| | | | _ \| | 3 / __| | | | |_) | | 4 | (__| |_| | _ <| |___ 5 \___|\___/|_| \_\_____| 6 7 libcurl's binary interface 8 9 ABI - Application Binary Interface 10 ---------------------------------- 11 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. 15 16 [Wikipedia has a longer description](http://en.wikipedia.org/wiki/Application_binary_interface) 17 18 Upgrades 19 -------- 20 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. 27 28 Version Numbers 29 --------------- 30 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. 33 34 Soname Bumps 35 ------------ 36 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. 44 45 During the first seven years of libcurl releases, there have only been four 46 ABI breakages. 47 48 We are determined to bump the SONAME as rarely as possible. Ideally, we 49 never do it again. 50 51 Downgrades 52 ---------- 53 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. 61 62 History 63 ------- 64 65 The previous major library soname number bumps (breaking backwards 66 compatibility) have happened the following times: 67 68 0 - libcurl 7.1, August 2000 69 70 1 - libcurl 7.5 December 2000 71 72 2 - libcurl 7.7 March 2001 73 74 3 - libcurl 7.12.0 June 2004 75 76 4 - libcurl 7.16.0 October 2006 77
