X-Git-Url: https://sigrok.org/gitweb/?p=libsigrokdecode.git;a=blobdiff_plain;f=decode.c;h=5289470670a227606666bdf0a7353769fd4bdab5;hp=6acbd10455f48da6dfb00516e4c94a3f3eb6ebb8;hb=4fa17efc0be6542055476bd7764fc04391bc652d;hpb=d842aebec31fd21fe0803cb9504ded698f6c1457

diff --git a/decode.c b/decode.c
index 6acbd10..5289470 100644
--- a/decode.c
+++ b/decode.c
@@ -34,6 +34,19 @@
 /* The list of protocol decoders. */
 GSList *list_pds = NULL;
 
+/*
+ * Here's a quick overview of Python/C API reference counting.
+ *
+ * Check the Python/C API docs for what type of reference a function returns.
+ *
+ *  - If it returns a "new reference", you're responsible to Py_DECREF() it.
+ *
+ *  - If it returns a "borrowed reference", you MUST NOT Py_DECREF() it.
+ *
+ *  - If a function "steals" a reference, you no longer are responsible for
+ *    Py_DECREF()ing it (someone else will do it for you at some point).
+ */
+
 /**
  * Initialize libsigrokdecode.
  *
@@ -86,7 +99,7 @@ GSList *sigrokdecode_list_decoders(void)
  *
  * TODO: @param entries.
  *
- * @return LIBSIGROKDECODE_OK upon success, a (negative) error code otherwise.
+ * @return SIGROKDECODE_OK upon success, a (negative) error code otherwise.
  *         The 'outstr' argument points to a malloc()ed string upon success.
  */
 static int h_str(PyObject *py_res, PyObject *py_func, PyObject *py_mod,
@@ -98,15 +111,20 @@ static int h_str(PyObject *py_res, PyObject *py_func, PyObject *py_mod,
 	py_str = PyMapping_GetItemString(py_res, (char *)key);
 	if (!py_str || !PyString_Check(py_str)) {
 		if (PyErr_Occurred())
-			PyErr_Print();
+			PyErr_Print(); /* Returns void. */
 		Py_DECREF(py_func);
 		Py_DECREF(py_mod);
 		return SIGROKDECODE_ERR_PYTHON; /* TODO: More specific error? */
 	}
 
+	/*
+	 * PyString_AsString()'s returned string refers to an internal buffer
+	 * (not a copy), i.e. the data must not be modified, and the memory
+	 * must not be free()'d.
+	 */
 	if (!(str = PyString_AsString(py_str))) {
 		if (PyErr_Occurred())
-			PyErr_Print();
+			PyErr_Print(); /* Returns void. */
 		Py_DECREF(py_str);
 		Py_DECREF(py_func);
 		Py_DECREF(py_mod);
@@ -115,7 +133,7 @@ static int h_str(PyObject *py_res, PyObject *py_func, PyObject *py_mod,
 
 	if (!(*outstr = strdup(str))) {
 		if (PyErr_Occurred())
-			PyErr_Print();
+			PyErr_Print(); /* Returns void. */
 		Py_DECREF(py_str);
 		Py_DECREF(py_func);
 		Py_DECREF(py_mod);
@@ -132,7 +150,7 @@ static int h_str(PyObject *py_res, PyObject *py_func, PyObject *py_mod,
  *
  * @param name TODO
  *
- * @return LIBSIGROKDECODE_OK upon success, a (negative) error code otherwise.
+ * @return SIGROKDECODE_OK upon success, a (negative) error code otherwise.
  */
 int sigrokdecode_load_decoder(const char *name,
 			      struct sigrokdecode_decoder **dec)
@@ -142,31 +160,31 @@ int sigrokdecode_load_decoder(const char *name,
 	int r;
 
 	/* Get the name of the decoder module as Python string. */
-	if (!(py_name = PyString_FromString(name))) {
-		PyErr_Print();
+	if (!(py_name = PyString_FromString(name))) { /* NEWREF */
+		PyErr_Print(); /* Returns void. */
 		return SIGROKDECODE_ERR_PYTHON; /* TODO: More specific error? */
 	}
 
 	/* "Import" the Python module. */
-	if (!(py_mod = PyImport_Import(py_name))) {
-		PyErr_Print();
+	if (!(py_mod = PyImport_Import(py_name))) { /* NEWREF */
+		PyErr_Print(); /* Returns void. */
 		Py_DECREF(py_name);
 		return SIGROKDECODE_ERR_PYTHON; /* TODO: More specific error? */
 	}
 	Py_DECREF(py_name);
 
 	/* Get the 'register' function name as Python callable object. */
-	py_func = PyObject_GetAttrString(py_mod, "register");
+	py_func = PyObject_GetAttrString(py_mod, "register"); /* NEWREF */
 	if (!py_func || !PyCallable_Check(py_func)) {
 		if (PyErr_Occurred())
-			PyErr_Print();
+			PyErr_Print(); /* Returns void. */
 		Py_DECREF(py_mod);
 		return SIGROKDECODE_ERR_PYTHON; /* TODO: More specific error? */
 	}
 
 	/* Call the 'register' function without arguments, get the result. */
-	if (!(py_res = PyObject_CallFunction(py_func, NULL))) {
-		PyErr_Print();
+	if (!(py_res = PyObject_CallFunction(py_func, NULL))) { /* NEWREF */
+		PyErr_Print(); /* Returns void. */
 		Py_DECREF(py_func);
 		Py_DECREF(py_mod);
 		return SIGROKDECODE_ERR_PYTHON; /* TODO: More specific error? */
@@ -190,10 +208,10 @@ int sigrokdecode_load_decoder(const char *name,
 	Py_DECREF(py_func);
 
 	/* Get the 'decode' function name as Python callable object. */
-	py_func = PyObject_GetAttrString(py_mod, "decode");
+	py_func = PyObject_GetAttrString(py_mod, "decode"); /* NEWREF */
 	if (!py_func || !PyCallable_Check(py_func)) {
 		if (PyErr_Occurred())
-			PyErr_Print();
+			PyErr_Print(); /* Returns void. */
 		Py_DECREF(py_mod);
 		return SIGROKDECODE_ERR_PYTHON; /* TODO: More specific error? */
 	}
@@ -216,7 +234,7 @@ int sigrokdecode_load_decoder(const char *name,
  * @param outbuf TODO
  * @param outbuflen TODO
  *
- * @return LIBSIGROKDECODE_OK upon success, a (negative) error code otherwise.
+ * @return SIGROKDECODE_OK upon success, a (negative) error code otherwise.
  */
 int sigrokdecode_run_decoder(struct sigrokdecode_decoder *dec,
 			     uint8_t *inbuf, uint64_t inbuflen,
@@ -241,13 +259,13 @@ int sigrokdecode_run_decoder(struct sigrokdecode_decoder *dec,
 
 	/* TODO: Error handling. */
 	py_mod = dec->py_mod;
+	Py_INCREF(py_mod);
 	py_func = dec->py_func;
-
-	/* TODO: Really run Py_DECREF on py_mod/py_func? */
+	Py_INCREF(py_func);
 
 	/* Create a Python tuple of size 1. */
-	if (!(py_args = PyTuple_New(1))) {
-		PyErr_Print();
+	if (!(py_args = PyTuple_New(1))) { /* NEWREF */
+		PyErr_Print(); /* Returns void. */
 		Py_DECREF(py_func);
 		Py_DECREF(py_mod);
 		return SIGROKDECODE_ERR_PYTHON; /* TODO: More specific error? */
@@ -255,26 +273,30 @@ int sigrokdecode_run_decoder(struct sigrokdecode_decoder *dec,
 
 	/* Get the input buffer as Python "string" (byte array). */
 	/* TODO: int vs. uint64_t for 'inbuflen'? */
-	if (!(py_value = Py_BuildValue("s#", inbuf, inbuflen))) {
-		PyErr_Print();
+	if (!(py_value = Py_BuildValue("s#", inbuf, inbuflen))) { /* NEWREF */
+		PyErr_Print(); /* Returns void. */
 		Py_DECREF(py_args);
 		Py_DECREF(py_func);
 		Py_DECREF(py_mod);
 		return SIGROKDECODE_ERR_PYTHON; /* TODO: More specific error? */
 	}
 
-	if (PyTuple_SetItem(py_args, 0, py_value) != 0) {
-		PyErr_Print();
-		Py_DECREF(py_value);
+	/*
+	 * IMPORTANT: PyTuple_SetItem() "steals" a reference to py_value!
+	 * That means we are no longer responsible for Py_DECREF()'ing it.
+	 * It will automatically be free'd when the 'py_args' tuple is free'd.
+	 */
+	if (PyTuple_SetItem(py_args, 0, py_value) != 0) { /* STEAL */
+		PyErr_Print(); /* Returns void. */
+		Py_DECREF(py_value); /* TODO: Ref. stolen upon error? */
 		Py_DECREF(py_args);
 		Py_DECREF(py_func);
 		Py_DECREF(py_mod);
 		return SIGROKDECODE_ERR_PYTHON; /* TODO: More specific error? */
 	}
 
-	if (!(py_res = PyObject_CallObject(py_func, py_args))) {
-		PyErr_Print();
-		Py_DECREF(py_value);
+	if (!(py_res = PyObject_CallObject(py_func, py_args))) { /* NEWREF */
+		PyErr_Print(); /* Returns void. */
 		Py_DECREF(py_args);
 		Py_DECREF(py_func);
 		Py_DECREF(py_mod);
@@ -283,9 +305,8 @@ int sigrokdecode_run_decoder(struct sigrokdecode_decoder *dec,
 
 	if ((ret = PyObject_AsCharBuffer(py_res, (const char **)outbuf,
 					 (Py_ssize_t *)outbuflen))) {
-		PyErr_Print();
+		PyErr_Print(); /* Returns void. */
 		Py_DECREF(py_res);
-		Py_DECREF(py_value);
 		Py_DECREF(py_args);
 		Py_DECREF(py_func);
 		Py_DECREF(py_mod);
@@ -293,7 +314,6 @@ int sigrokdecode_run_decoder(struct sigrokdecode_decoder *dec,
 	}
 
 	Py_DECREF(py_res);
-	// Py_DECREF(py_value);
 	Py_DECREF(py_args);
 	Py_DECREF(py_func);
 	Py_DECREF(py_mod);
@@ -304,7 +324,7 @@ int sigrokdecode_run_decoder(struct sigrokdecode_decoder *dec,
 /**
  * Shutdown libsigrokdecode.
  *
- * @return LIBSIGROKDECODE_OK upon success, a (negative) error code otherwise.
+ * @return SIGROKDECODE_OK upon success, a (negative) error code otherwise.
  */
 int sigrokdecode_shutdown(void)
 {