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https://github.com/moparisthebest/curl
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69 lines
2.4 KiB
Plaintext
69 lines
2.4 KiB
Plaintext
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curl_off_t explained
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====================
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curl_off_t is a data type provided by the external libcurl include headers. It
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is the type meant to be used for the curl_easy_setopt() options that end with
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LARGE. The type is 64bit large on most modern platforms.
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Transition from < 7.19.0 to >= 7.19.0
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-------------------------------------
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Applications that used libcurl before 7.19.0 that are rebuilt with a libcurl
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that is 7.19.0 or later may or may not have to worry about anything of
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this. We have made a significant effort to make the transition really seamless
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and transparent.
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You have have to take notice if you are in one of the following situations:
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o Your app is using or will after the transition use a libcurl that is built
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with LFS (large file support) disabled even though your system otherwise
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supports it.
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o Your app is using or will after the transition use a libcurl that doesn't
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support LFS at all, but your system and compiler support 64bit data types.
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In both these cases, the curl_off_t type will now (after the transition) be
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64bit where it previously was 32bit. This will cause a binary incompatibility
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that you MAY need to deal with.
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Benefits
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--------
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This new way has several benefits:
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o Platforms without LFS support can still use libcurl to do >32 bit file
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transfers and range operations etc as long as they have >32 bit data-types
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supported.
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o Applications will no longer easily build with the curl_off_t size
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mismatched, which has been a very frequent (and annoying) problem with
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libcurl <= 7.18.2
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Historically
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------------
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Previously, before 7.19.0, the curl_off_t type would be rather strongly
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connected to the size of the system off_t type, where currently curl_off_t is
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independent of that.
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The strong connection to off_t made it troublesome for application authors
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since when they did mistakes, they could get curl_off_t type of different
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sizes in the app vs libcurl, and that caused strange effects that were hard to
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track and detect by users of libcurl.
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SONAME
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------
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We opted to not bump the soname for the library unconditionally, simply
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because soname bumping is causing a lot of grief and moaning all over the
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community so we try to keep that at minimum. Also, our selected design path
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should be 100% backwards compatible for the vast majority of all libcurl
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users.
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Enforce SONAME bump
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-------------------
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If configure doesn't detect your case where a bump is necessary, re-run it
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with the --enable-soname-bump command line option!
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