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README.curl_off_t 2.4 KB

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  1. curl_off_t explained
  2. ====================
  3. curl_off_t is a data type provided by the external libcurl include headers. It
  4. is the type meant to be used for the curl_easy_setopt() options that end with
  5. LARGE. The type is 64bit large on most modern platforms.
  6. Transition from < 7.19.0 to >= 7.19.0
  7. -------------------------------------
  8. Applications that used libcurl before 7.19.0 that are rebuilt with a libcurl
  9. that is 7.19.0 or later may or may not have to worry about anything of
  10. this. We have made a significant effort to make the transition really seamless
  11. and transparent.
  12. You have have to take notice if you are in one of the following situations:
  13. o Your app is using or will after the transition use a libcurl that is built
  14. with LFS (large file support) disabled even though your system otherwise
  15. supports it.
  16. o Your app is using or will after the transition use a libcurl that doesn't
  17. support LFS at all, but your system and compiler support 64bit data types.
  18. In both these cases, the curl_off_t type will now (after the transition) be
  19. 64bit where it previously was 32bit. This will cause a binary incompatibility
  20. that you MAY need to deal with.
  21. Benefits
  22. --------
  23. This new way has several benefits:
  24. o Platforms without LFS support can still use libcurl to do >32 bit file
  25. transfers and range operations etc as long as they have >32 bit data-types
  26. supported.
  27. o Applications will no longer easily build with the curl_off_t size
  28. mismatched, which has been a very frequent (and annoying) problem with
  29. libcurl <= 7.18.2
  30. Historically
  31. ------------
  32. Previously, before 7.19.0, the curl_off_t type would be rather strongly
  33. connected to the size of the system off_t type, where currently curl_off_t is
  34. independent of that.
  35. The strong connection to off_t made it troublesome for application authors
  36. since when they did mistakes, they could get curl_off_t type of different
  37. sizes in the app vs libcurl, and that caused strange effects that were hard to
  38. track and detect by users of libcurl.
  39. SONAME
  40. ------
  41. We opted to not bump the soname for the library unconditionally, simply
  42. because soname bumping is causing a lot of grief and moaning all over the
  43. community so we try to keep that at minimum. Also, our selected design path
  44. should be 100% backwards compatible for the vast majority of all libcurl
  45. users.
  46. Enforce SONAME bump
  47. -------------------
  48. If configure doesn't detect your case where a bump is necessary, re-run it
  49. with the --enable-soname-bump command line option!