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Diffstat (limited to 'cffi/_embedding.h')
| -rw-r--r-- | cffi/_embedding.h | 484 |
1 files changed, 484 insertions, 0 deletions
diff --git a/cffi/_embedding.h b/cffi/_embedding.h new file mode 100644 index 0000000..3953cd7 --- /dev/null +++ b/cffi/_embedding.h @@ -0,0 +1,484 @@ + +/***** Support code for embedding *****/ + +#ifdef __cplusplus +extern "C" { +#endif + + +#if defined(_WIN32) +# define CFFI_DLLEXPORT __declspec(dllexport) +#elif defined(__GNUC__) +# define CFFI_DLLEXPORT __attribute__((visibility("default"))) +#else +# define CFFI_DLLEXPORT /* nothing */ +#endif + + +/* There are two global variables of type _cffi_call_python_fnptr: + + * _cffi_call_python, which we declare just below, is the one called + by ``extern "Python"`` implementations. + + * _cffi_call_python_org, which on CPython is actually part of the + _cffi_exports[] array, is the function pointer copied from + _cffi_backend. + + After initialization is complete, both are equal. However, the + first one remains equal to &_cffi_start_and_call_python until the + very end of initialization, when we are (or should be) sure that + concurrent threads also see a completely initialized world, and + only then is it changed. +*/ +#undef _cffi_call_python +typedef void (*_cffi_call_python_fnptr)(struct _cffi_externpy_s *, char *); +static void _cffi_start_and_call_python(struct _cffi_externpy_s *, char *); +static _cffi_call_python_fnptr _cffi_call_python = &_cffi_start_and_call_python; + + +#ifndef _MSC_VER + /* --- Assuming a GCC not infinitely old --- */ +# define cffi_compare_and_swap(l,o,n) __sync_bool_compare_and_swap(l,o,n) +# define cffi_write_barrier() __sync_synchronize() +# if !defined(__amd64__) && !defined(__x86_64__) && \ + !defined(__i386__) && !defined(__i386) +# define cffi_read_barrier() __sync_synchronize() +# else +# define cffi_read_barrier() (void)0 +# endif +#else + /* --- Windows threads version --- */ +# include <Windows.h> +# define cffi_compare_and_swap(l,o,n) \ + (InterlockedCompareExchangePointer(l,n,o) == (o)) +# define cffi_write_barrier() InterlockedCompareExchange(&_cffi_dummy,0,0) +# define cffi_read_barrier() (void)0 +static volatile LONG _cffi_dummy; +#endif + +#ifdef WITH_THREAD +# ifndef _MSC_VER +# include <pthread.h> + static pthread_mutex_t _cffi_embed_startup_lock; +# else + static CRITICAL_SECTION _cffi_embed_startup_lock; +# endif + static char _cffi_embed_startup_lock_ready = 0; +#endif + +static void _cffi_acquire_reentrant_mutex(void) +{ + static void *volatile lock = NULL; + + while (!cffi_compare_and_swap(&lock, NULL, (void *)1)) { + /* should ideally do a spin loop instruction here, but + hard to do it portably and doesn't really matter I + think: pthread_mutex_init() should be very fast, and + this is only run at start-up anyway. */ + } + +#ifdef WITH_THREAD + if (!_cffi_embed_startup_lock_ready) { +# ifndef _MSC_VER + pthread_mutexattr_t attr; + pthread_mutexattr_init(&attr); + pthread_mutexattr_settype(&attr, PTHREAD_MUTEX_RECURSIVE); + pthread_mutex_init(&_cffi_embed_startup_lock, &attr); +# else + InitializeCriticalSection(&_cffi_embed_startup_lock); +# endif + _cffi_embed_startup_lock_ready = 1; + } +#endif + + while (!cffi_compare_and_swap(&lock, (void *)1, NULL)) + ; + +#ifndef _MSC_VER + pthread_mutex_lock(&_cffi_embed_startup_lock); +#else + EnterCriticalSection(&_cffi_embed_startup_lock); +#endif +} + +static void _cffi_release_reentrant_mutex(void) +{ +#ifndef _MSC_VER + pthread_mutex_unlock(&_cffi_embed_startup_lock); +#else + LeaveCriticalSection(&_cffi_embed_startup_lock); +#endif +} + + +/********** CPython-specific section **********/ +#ifndef PYPY_VERSION + +#include "_cffi_errors.h" + + +#define _cffi_call_python_org _cffi_exports[_CFFI_CPIDX] + +PyMODINIT_FUNC _CFFI_PYTHON_STARTUP_FUNC(void); /* forward */ + +static void _cffi_py_initialize(void) +{ + /* XXX use initsigs=0, which "skips initialization registration of + signal handlers, which might be useful when Python is + embedded" according to the Python docs. But review and think + if it should be a user-controllable setting. + + XXX we should also give a way to write errors to a buffer + instead of to stderr. + + XXX if importing 'site' fails, CPython (any version) calls + exit(). Should we try to work around this behavior here? + */ + Py_InitializeEx(0); +} + +static int _cffi_initialize_python(void) +{ + /* This initializes Python, imports _cffi_backend, and then the + present .dll/.so is set up as a CPython C extension module. + */ + int result; + PyGILState_STATE state; + PyObject *pycode=NULL, *global_dict=NULL, *x; + + state = PyGILState_Ensure(); + + /* Call the initxxx() function from the present module. It will + create and initialize us as a CPython extension module, instead + of letting the startup Python code do it---it might reimport + the same .dll/.so and get maybe confused on some platforms. + It might also have troubles locating the .dll/.so again for all + I know. + */ + (void)_CFFI_PYTHON_STARTUP_FUNC(); + if (PyErr_Occurred()) + goto error; + + /* Now run the Python code provided to ffi.embedding_init_code(). + */ + pycode = Py_CompileString(_CFFI_PYTHON_STARTUP_CODE, + "<init code for '" _CFFI_MODULE_NAME "'>", + Py_file_input); + if (pycode == NULL) + goto error; + global_dict = PyDict_New(); + if (global_dict == NULL) + goto error; + if (PyDict_SetItemString(global_dict, "__builtins__", + PyThreadState_GET()->interp->builtins) < 0) + goto error; + x = PyEval_EvalCode( +#if PY_MAJOR_VERSION < 3 + (PyCodeObject *) +#endif + pycode, global_dict, global_dict); + if (x == NULL) + goto error; + Py_DECREF(x); + + /* Done! Now if we've been called from + _cffi_start_and_call_python() in an ``extern "Python"``, we can + only hope that the Python code did correctly set up the + corresponding @ffi.def_extern() function. Otherwise, the + general logic of ``extern "Python"`` functions (inside the + _cffi_backend module) will find that the reference is still + missing and print an error. + */ + result = 0; + done: + Py_XDECREF(pycode); + Py_XDECREF(global_dict); + PyGILState_Release(state); + return result; + + error:; + { + /* Print as much information as potentially useful. + Debugging load-time failures with embedding is not fun + */ + PyObject *ecap; + PyObject *exception, *v, *tb, *f, *modules, *mod; + PyErr_Fetch(&exception, &v, &tb); + ecap = _cffi_start_error_capture(); + f = PySys_GetObject((char *)"stderr"); + if (f != NULL && f != Py_None) { + PyFile_WriteString( + "Failed to initialize the Python-CFFI embedding logic:\n\n", f); + } + + if (exception != NULL) { + PyErr_NormalizeException(&exception, &v, &tb); + PyErr_Display(exception, v, tb); + } + Py_XDECREF(exception); + Py_XDECREF(v); + Py_XDECREF(tb); + + if (f != NULL && f != Py_None) { + PyFile_WriteString("\nFrom: " _CFFI_MODULE_NAME + "\ncompiled with cffi version: 1.12.2" + "\n_cffi_backend module: ", f); + modules = PyImport_GetModuleDict(); + mod = PyDict_GetItemString(modules, "_cffi_backend"); + if (mod == NULL) { + PyFile_WriteString("not loaded", f); + } + else { + v = PyObject_GetAttrString(mod, "__file__"); + PyFile_WriteObject(v, f, 0); + Py_XDECREF(v); + } + PyFile_WriteString("\nsys.path: ", f); + PyFile_WriteObject(PySys_GetObject((char *)"path"), f, 0); + PyFile_WriteString("\n\n", f); + } + _cffi_stop_error_capture(ecap); + } + result = -1; + goto done; +} + +PyAPI_DATA(char *) _PyParser_TokenNames[]; /* from CPython */ + +static int _cffi_carefully_make_gil(void) +{ + /* This does the basic initialization of Python. It can be called + completely concurrently from unrelated threads. It assumes + that we don't hold the GIL before (if it exists), and we don't + hold it afterwards. + + (What it really does used to be completely different in Python 2 + and Python 3, with the Python 2 solution avoiding the spin-lock + around the Py_InitializeEx() call. However, after recent changes + to CPython 2.7 (issue #358) it no longer works. So we use the + Python 3 solution everywhere.) + + This initializes Python by calling Py_InitializeEx(). + Important: this must not be called concurrently at all. + So we use a global variable as a simple spin lock. This global + variable must be from 'libpythonX.Y.so', not from this + cffi-based extension module, because it must be shared from + different cffi-based extension modules. We choose + _PyParser_TokenNames[0] as a completely arbitrary pointer value + that is never written to. The default is to point to the + string "ENDMARKER". We change it temporarily to point to the + next character in that string. (Yes, I know it's REALLY + obscure.) + */ + +#ifdef WITH_THREAD + char *volatile *lock = (char *volatile *)_PyParser_TokenNames; + char *old_value; + + while (1) { /* spin loop */ + old_value = *lock; + if (old_value[0] == 'E') { + assert(old_value[1] == 'N'); + if (cffi_compare_and_swap(lock, old_value, old_value + 1)) + break; + } + else { + assert(old_value[0] == 'N'); + /* should ideally do a spin loop instruction here, but + hard to do it portably and doesn't really matter I + think: PyEval_InitThreads() should be very fast, and + this is only run at start-up anyway. */ + } + } +#endif + + /* call Py_InitializeEx() */ + { + PyGILState_STATE state = PyGILState_UNLOCKED; + if (!Py_IsInitialized()) + _cffi_py_initialize(); + else + state = PyGILState_Ensure(); + + PyEval_InitThreads(); + PyGILState_Release(state); + } + +#ifdef WITH_THREAD + /* release the lock */ + while (!cffi_compare_and_swap(lock, old_value + 1, old_value)) + ; +#endif + + return 0; +} + +/********** end CPython-specific section **********/ + + +#else + + +/********** PyPy-specific section **********/ + +PyMODINIT_FUNC _CFFI_PYTHON_STARTUP_FUNC(const void *[]); /* forward */ + +static struct _cffi_pypy_init_s { + const char *name; + void (*func)(const void *[]); + const char *code; +} _cffi_pypy_init = { + _CFFI_MODULE_NAME, + (void(*)(const void *[]))_CFFI_PYTHON_STARTUP_FUNC, + _CFFI_PYTHON_STARTUP_CODE, +}; + +extern int pypy_carefully_make_gil(const char *); +extern int pypy_init_embedded_cffi_module(int, struct _cffi_pypy_init_s *); + +static int _cffi_carefully_make_gil(void) +{ + return pypy_carefully_make_gil(_CFFI_MODULE_NAME); +} + +static int _cffi_initialize_python(void) +{ + return pypy_init_embedded_cffi_module(0xB011, &_cffi_pypy_init); +} + +/********** end PyPy-specific section **********/ + + +#endif + + +#ifdef __GNUC__ +__attribute__((noinline)) +#endif +static _cffi_call_python_fnptr _cffi_start_python(void) +{ + /* Delicate logic to initialize Python. This function can be + called multiple times concurrently, e.g. when the process calls + its first ``extern "Python"`` functions in multiple threads at + once. It can also be called recursively, in which case we must + ignore it. We also have to consider what occurs if several + different cffi-based extensions reach this code in parallel + threads---it is a different copy of the code, then, and we + can't have any shared global variable unless it comes from + 'libpythonX.Y.so'. + + Idea: + + * _cffi_carefully_make_gil(): "carefully" call + PyEval_InitThreads() (possibly with Py_InitializeEx() first). + + * then we use a (local) custom lock to make sure that a call to this + cffi-based extension will wait if another call to the *same* + extension is running the initialization in another thread. + It is reentrant, so that a recursive call will not block, but + only one from a different thread. + + * then we grab the GIL and (Python 2) we call Py_InitializeEx(). + At this point, concurrent calls to Py_InitializeEx() are not + possible: we have the GIL. + + * do the rest of the specific initialization, which may + temporarily release the GIL but not the custom lock. + Only release the custom lock when we are done. + */ + static char called = 0; + + if (_cffi_carefully_make_gil() != 0) + return NULL; + + _cffi_acquire_reentrant_mutex(); + + /* Here the GIL exists, but we don't have it. We're only protected + from concurrency by the reentrant mutex. */ + + /* This file only initializes the embedded module once, the first + time this is called, even if there are subinterpreters. */ + if (!called) { + called = 1; /* invoke _cffi_initialize_python() only once, + but don't set '_cffi_call_python' right now, + otherwise concurrent threads won't call + this function at all (we need them to wait) */ + if (_cffi_initialize_python() == 0) { + /* now initialization is finished. Switch to the fast-path. */ + + /* We would like nobody to see the new value of + '_cffi_call_python' without also seeing the rest of the + data initialized. However, this is not possible. But + the new value of '_cffi_call_python' is the function + 'cffi_call_python()' from _cffi_backend. So: */ + cffi_write_barrier(); + /* ^^^ we put a write barrier here, and a corresponding + read barrier at the start of cffi_call_python(). This + ensures that after that read barrier, we see everything + done here before the write barrier. + */ + + assert(_cffi_call_python_org != NULL); + _cffi_call_python = (_cffi_call_python_fnptr)_cffi_call_python_org; + } + else { + /* initialization failed. Reset this to NULL, even if it was + already set to some other value. Future calls to + _cffi_start_python() are still forced to occur, and will + always return NULL from now on. */ + _cffi_call_python_org = NULL; + } + } + + _cffi_release_reentrant_mutex(); + + return (_cffi_call_python_fnptr)_cffi_call_python_org; +} + +static +void _cffi_start_and_call_python(struct _cffi_externpy_s *externpy, char *args) +{ + _cffi_call_python_fnptr fnptr; + int current_err = errno; +#ifdef _MSC_VER + int current_lasterr = GetLastError(); +#endif + fnptr = _cffi_start_python(); + if (fnptr == NULL) { + fprintf(stderr, "function %s() called, but initialization code " + "failed. Returning 0.\n", externpy->name); + memset(args, 0, externpy->size_of_result); + } +#ifdef _MSC_VER + SetLastError(current_lasterr); +#endif + errno = current_err; + + if (fnptr != NULL) + fnptr(externpy, args); +} + + +/* The cffi_start_python() function makes sure Python is initialized + and our cffi module is set up. It can be called manually from the + user C code. The same effect is obtained automatically from any + dll-exported ``extern "Python"`` function. This function returns + -1 if initialization failed, 0 if all is OK. */ +_CFFI_UNUSED_FN +static int cffi_start_python(void) +{ + if (_cffi_call_python == &_cffi_start_and_call_python) { + if (_cffi_start_python() == NULL) + return -1; + } + cffi_read_barrier(); + return 0; +} + +#undef cffi_compare_and_swap +#undef cffi_write_barrier +#undef cffi_read_barrier + +#ifdef __cplusplus +} +#endif |