What’s New


  • ffi.gc(): fixed a race condition in multithreaded programs introduced in 1.1.1


  • Out-of-line mode: ffi.string(), ffi.buffer() and ffi.getwinerror() didn’t accept their arguments as keyword arguments, unlike their in-line mode equivalent. (It worked in PyPy.)
  • Out-of-line ABI mode: documented a restriction of ffi.dlopen() when compared to the in-line mode.
  • ffi.gc(): when called several times with equal pointers, it was accidentally registering only the last destructor, or even none at all depending on details. (It was correctly registering all of them only in PyPy, and only with the out-of-line FFIs.)


  • Out-of-line API mode: we can now declare integer types with typedef int... foo_t;. The exact size and signedness of foo_t is figured out by the compiler.
  • Out-of-line API mode: we can now declare multidimensional arrays (as fields or as globals) with int n[...][...]. Before, only the outermost dimension would support the ... syntax.
  • Out-of-line ABI mode: we now support any constant declaration, instead of only integers whose value is given in the cdef. Such “new” constants, i.e. either non-integers or without a value given in the cdef, must correspond to actual symbols in the lib. At runtime they are looked up the first time we access them. This is useful if the library defines extern const sometype somename;.
  • ffi.addressof(lib, "func_name") now returns a regular cdata object of type “pointer to function”. You can use it on any function from a library in API mode (in ABI mode, all functions are already regular cdata objects). To support this, you need to recompile your cffi modules.
  • Issue #198: in API mode, if you declare constants of a struct type, what you saw from lib.CONSTANT was corrupted.
  • Issue #196: ffi.set_source("package._ffi", None) would incorrectly generate the Python source to package._ffi.py instead of package/_ffi.py. Also fixed: in some cases, if the C file was in build/foo.c, the .o file would be put in build/build/foo.o.


  • Same as 1.0.2, apart from doc and test fixes on some platforms.


  • Variadic C functions (ending in a ”...” argument) were not supported in the out-of-line ABI mode. This was a bug—there was even a (non-working) example doing exactly that!


  • ffi.set_source() crashed if passed a sources=[..] argument. Fixed by chrippa on pull request #60.
  • Issue #193: if we use a struct between the first cdef() where it is declared and another cdef() where its fields are defined, then this definition was ignored.
  • Enums were buggy if you used too many ”...” in their definition.


  • The main news item is out-of-line module generation:
  • (this page will list what is new from all versions from 1.0.0 forward.)