2007-10-04 18:05:25 -04:00
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_ _ ____ _
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/ __| | | | |_) | |
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| (__| |_| | _ <| |___
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\___|\___/|_| \_\_____|
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libcurl's binary interface
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2007-10-05 11:18:34 -04:00
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ABI - Application Binary Interface
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2007-10-04 18:05:25 -04:00
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First, allow me to define the word for this context: ABI describes the
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low-level interface between an application program a library. Calling
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conventions, function arguments, return values, struct sizes/defines and
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more.
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2007-10-05 11:18:34 -04:00
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For a longer descricption, see
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http://en.wikipedia.org/wiki/Application_binary_interface
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2007-10-04 18:05:25 -04:00
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Upgrades
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In the vast majority of all cases, a typical libcurl upgrade does not break
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the ABI at all. Your application can remain using libcurl just as before,
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only with less bugs and possibly with added new features. You need to read
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the release notes, and if they mention an ABI break/soname bump, you may
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have to verify that your application still builds fine and uses libcurl as
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it now is defined to work.
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Version Numbers
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In libcurl land, you really can't tell by the libcurl version number if that
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libcurl is binary compatible or not with another libcurl version.
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Soname Bumps
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Whenever there are changes done to the library that will cause an ABI
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breakage, that may require your application to get attention or possibly be
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changed to adhere to new things, we will bump the soname. Then the library
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will get a different output name and thus can in fact be installed in
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parallell with an older installed lib (on most systems). Thus, old
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applications built against the previous ABI version will remain working and
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using the older lib, while newer applications build and use the newer one.
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During the first seven years of libcurl releases, there have only been four
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ABI breakages.
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Downgrades
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Going to an older libcurl version from one you're currently using can be a
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tricky thing. Mostly we add features and options to newer libcurls as that
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won't break ABI or hamper existing applications. This has the implication
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that going backwards may get you in a situation where you pick a libcurl
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that doesn't support the options your application needs. Or possibly you
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even downgrade so far so you cross an ABI break border and thus a different
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soname, and then your application may need to adapt to the modified ABI.
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