Python: Restrict code to stable ABI subset

Limit usage of the Python C API to the stable ABI subset as defined
by PEP 384. This removes some type definitions and functions which
libsigrokdecode made use of. Convert all affected code to suitable
API alternatives. Also fix a few leaks that became apparent while
working on the code.

The most visible change is that PyTypeObject is now an opaque type.
Thus, the custom Decoder and srd_logic types are now created on the
heap via an alternative API. Unfortunately, since tp_name is now
inaccessible, type names had to be removed from the log output.

Stack traces after Python exceptions are now formatted by calling
into Python, since the trace object C API is no longer available.

1 files changed, 13 insertions, 6 deletions

diff --git a/libsigrokdecode-internal.h b/libsigrokdecode-internal.h
index bcf6bb7..fa8e91c 100644
--- a/libsigrokdecode-internal.h
+++ b/libsigrokdecode-internal.h
@@ -22,6 +22,9 @@
 #ifndef LIBSIGROKDECODE_LIBSIGROKDECODE_INTERNAL_H
 #define LIBSIGROKDECODE_LIBSIGROKDECODE_INTERNAL_H
 
+/* Use the stable ABI subset as per PEP 384. */
+#define Py_LIMITED_API 0x03020000
+
 #include <Python.h> /* First, so we avoid a _POSIX_C_SOURCE warning. */
 #include "libsigrokdecode.h"
 
@@ -83,16 +86,20 @@ SRD_PRIV int srd_log(int loglevel, const char *format, ...) G_GNUC_PRINTF(2, 3);
 #define srd_warn(...)	srd_log(SRD_LOG_WARN, __VA_ARGS__)
 #define srd_err(...)	srd_log(SRD_LOG_ERR,  __VA_ARGS__)
 
+/* type_decoder.c */
+SRD_PRIV PyObject *srd_Decoder_type_new(void);
+
+/* type_logic.c */
+SRD_PRIV PyObject *srd_logic_type_new(void);
+
 /* module_sigrokdecode.c */
 PyMODINIT_FUNC PyInit_sigrokdecode(void);
 
 /* util.c */
-SRD_PRIV int py_attr_as_str(const PyObject *py_obj, const char *attr,
-        char **outstr);
-SRD_PRIV int py_dictitem_as_str(const PyObject *py_obj, const char *key,
-        char **outstr);
-SRD_PRIV int py_str_as_str(const PyObject *py_str, char **outstr);
-SRD_PRIV int py_strseq_to_char(const PyObject *py_strseq, char ***outstr);
+SRD_PRIV int py_attr_as_str(PyObject *py_obj, const char *attr, char **outstr);
+SRD_PRIV int py_dictitem_as_str(PyObject *py_obj, const char *key, char **outstr);
+SRD_PRIV int py_str_as_str(PyObject *py_str, char **outstr);
+SRD_PRIV int py_strseq_to_char(PyObject *py_strseq, char ***out_strv);
 
 /* exception.c */
 SRD_PRIV void srd_exception_catch(const char *format, ...);