What’s New


Nothing changed from v1.2.0.


  • Out-of-line mode: int a[][...]; can be used to declare a structure field or global variable which is, simultaneously, of total length unknown to the C compiler (the a[] part) and each element is itself an array of N integers, where the value of N is known to the C compiler (the int and [...] parts around it). Similarly, int a[5][...]; is supported (but probably less useful: remember that in C it means int (a[5])[...];).
  • PyPy: the lib.some_function objects were missing the attributes __name__, __module__ and __doc__ that are expected e.g. by some decorators-management functions from functools.
  • Out-of-line API mode: you can now do from _example.lib import x to import the name x from _example.lib, even though the lib object is not a standard module object. (Also works in from _example.lib import *, but this is even more of a hack and will fail if lib happens to declare a name called __all__. Note that * excludes the global variables; only the functions and constants make sense to import like this.)
  • lib.__dict__ works again and gives you a copy of the dict—assuming that lib has got no symbol called precisely __dict__. (In general, it is safer to use dir(lib).)
  • Out-of-line API mode: global variables are now fetched on demand at every access. It fixes issue #212 (Windows DLL variables), and also allows variables that are defined as dynamic macros (like errno) or __thread -local variables. (This change might also tighten the C compiler’s check on the variables’ type.)
  • Issue #209: dereferencing NULL pointers now raises RuntimeError instead of segfaulting. Meant as a debugging aid. The check is only for NULL: if you dereference random or dead pointers you might still get segfaults.
  • Issue #152: callbacks: added an argument ffi.callback(..., onerror=...). If the main callback function raises an exception and onerror is provided, then onerror(exception, exc_value, traceback) is called. This is similar to writing a try: except: in the main callback function, but in some cases (e.g. a signal) an exception can occur at the very start of the callback function—before it had time to enter the try: except: block.
  • Issue #115: added ffi.new_allocator(), which officializes support for alternative allocators.


  • 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.)