69 lines
2.5 KiB
Markdown
69 lines
2.5 KiB
Markdown
|
<!--
|
||
|
|
Copyright (C) Daniel Stenberg, <daniel@haxx.se>, et al.
|
||
|
|
|
||
|
|
SPDX-License-Identifier: curl
|
||
|
|
-->
|
||
|
|
|
||
|
|
ABI - Application Binary Interface
|
||
|
|
==================================
|
||
|
|
|
||
|
|
"ABI" describes the low-level interface between an application program and a
|
||
|
|
library. Calling conventions, function arguments, return values, struct
|
||
|
|
sizes/defines and more.
|
||
|
|
|
||
|
|
[Wikipedia has a longer description](https://en.wikipedia.org/wiki/Application_binary_interface)
|
||
|
|
|
||
|
|
## Upgrades
|
||
|
|
|
||
|
|
A libcurl upgrade does not break the ABI or change established and documented
|
||
|
|
behavior. Your application can remain using libcurl just as before, only with
|
||
|
|
fewer bugs and possibly with added new features.
|
||
|
|
|
||
|
|
## Version Numbers
|
||
|
|
|
||
|
|
In libcurl land, you cannot tell by the libcurl version number if that
|
||
|
|
libcurl is binary compatible or not with another libcurl version. As a rule,
|
||
|
|
we do not break the ABI so you can *always* upgrade to a later version without
|
||
|
|
any loss or change in functionality.
|
||
|
|
|
||
|
|
## 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
|
||
|
|
changed to adhere to new things, we will bump the SONAME. Then the library
|
||
|
|
will get a different output name and thus can in fact be installed in
|
||
|
|
parallel with an older installed lib (on most systems). Thus, old
|
||
|
|
applications built against the previous ABI version will remain working and
|
||
|
|
using the older lib, while newer applications build and use the newer one.
|
||
|
|
|
||
|
|
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 are currently using can be a
|
||
|
|
tricky thing. Mostly we add features and options to newer libcurls as that
|
||
|
|
will not break ABI or hamper existing applications. This has the implication
|
||
|
|
that going backwards may get you in a situation where you pick a libcurl that
|
||
|
|
does not support the options your application needs. Or possibly you even
|
||
|
|
downgrade so far so you cross an ABI break border and thus a different
|
||
|
|
SONAME, and then your application may need to adapt to the modified ABI.
|
||
|
|
|
||
|
|
## History
|
||
|
|
|
||
|
|
The previous major library SONAME number bumps (breaking backwards
|
||
|
|
compatibility) happened the following times:
|
||
|
|
|
||
|
|
0 - libcurl 7.1, August 2000
|
||
|
|
|
||
|
|
1 - libcurl 7.5 December 2000
|
||
|
|
|
||
|
|
2 - libcurl 7.7 March 2001
|
||
|
|
|
||
|
|
3 - libcurl 7.12.0 June 2004
|
||
|
|
|
||
|
|
4 - libcurl 7.16.0 October 2006
|