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