index parser: fix refcounting in case of errors, refactor

due to incorrect refcounting, on a bad revlog it was failing with:
*** glibc detected *** /usr/bin/python: corrupted double-linked list: 0x0816d318 ***
and a backtrace.

mercurial/parsers.c

@@ -1,414 +1,426 b''
 /*
  parsers.c - efficient content parsing
 
  Copyright 2008 Matt Mackall <[e-mail]> and others
 
  This software may be used and distributed according to the terms of
  the GNU General Public License, incorporated herein by reference.
 */
 
 #include <Python.h>
 #include <ctype.h>
 #include <string.h>
 
 static int hexdigit(char c)
 {
 	if (c >= '0' && c <= '9')
 		return c - '0';
 	if (c >= 'a' && c <= 'f')
 		return c - 'a' + 10;
 	if (c >= 'A' && c <= 'F')
 		return c - 'A' + 10;
 
 	PyErr_SetString(PyExc_ValueError, "input contains non-hex character");
 	return 0;
 }
 
 /*
  * Turn a hex-encoded string into binary.
  */
 static PyObject *unhexlify(const char *str, int len)
 {
 	PyObject *ret;
 	const char *c;
 	char *d;
 
 	ret = PyString_FromStringAndSize(NULL, len / 2);
 	if (!ret)
 		return NULL;
 
 	d = PyString_AS_STRING(ret);
 	for (c = str; c < str + len;) {
 		int hi = hexdigit(*c++);
 		int lo = hexdigit(*c++);
 		*d++ = (hi << 4) | lo;
 	}
 
 	return ret;
 }
 
 /*
  * This code assumes that a manifest is stitched together with newline
  * ('\n') characters.
  */
 static PyObject *parse_manifest(PyObject *self, PyObject *args)
 {
 	PyObject *mfdict, *fdict;
 	char *str, *cur, *start, *zero;
 	int len;
 
 	if (!PyArg_ParseTuple(args, "O!O!s#:parse_manifest",
 			      &PyDict_Type, &mfdict,
 			      &PyDict_Type, &fdict,
 			      &str, &len))
 		goto quit;
 
 	for (start = cur = str, zero = NULL; cur < str + len; cur++) {
 		PyObject *file = NULL, *node = NULL;
 		PyObject *flags = NULL;
 		int nlen;
 
 		if (!*cur) {
 			zero = cur;
 			continue;
 		}
 		else if (*cur != '\n')
 			continue;
 
 		if (!zero) {
 			PyErr_SetString(PyExc_ValueError,
 					"manifest entry has no separator");
 			goto quit;
 		}
 
 		file = PyString_FromStringAndSize(start, zero - start);
 		if (!file)
 			goto bail;
 
 		nlen = cur - zero - 1;
 
 		node = unhexlify(zero + 1, nlen > 40 ? 40 : nlen);
 		if (!node)
 			goto bail;
 
 		if (nlen > 40) {
 			PyObject *flags;
 
 			flags = PyString_FromStringAndSize(zero + 41,
 							   nlen - 40);
 			if (!flags)
 				goto bail;
 
 			if (PyDict_SetItem(fdict, file, flags) == -1)
 				goto bail;
 		}
 
 		if (PyDict_SetItem(mfdict, file, node) == -1)
 			goto bail;
 
 		start = cur + 1;
 		zero = NULL;
 
 		Py_XDECREF(flags);
 		Py_XDECREF(node);
 		Py_XDECREF(file);
 		continue;
 	bail:
 		Py_XDECREF(flags);
 		Py_XDECREF(node);
 		Py_XDECREF(file);
 		goto quit;
 	}
 
 	if (len > 0 && *(cur - 1) != '\n') {
 		PyErr_SetString(PyExc_ValueError,
 				"manifest contains trailing garbage");
 		goto quit;
 	}
 
 	Py_INCREF(Py_None);
 	return Py_None;
 quit:
 	return NULL;
 }
 
 #ifdef _WIN32
 # ifdef _MSC_VER
 /* msvc 6.0 has problems */
 #  define inline __inline
 typedef unsigned long uint32_t;
 typedef unsigned __int64 uint64_t;
 # else
 #  include <stdint.h>
 # endif
 static uint32_t ntohl(uint32_t x)
 {
 	return ((x & 0x000000ffUL) << 24) |
 		((x & 0x0000ff00UL) <<  8) |
 		((x & 0x00ff0000UL) >>  8) |
 		((x & 0xff000000UL) >> 24);
 }
 #else
 /* not windows */
 # include <sys/types.h>
 # if defined __BEOS__ && !defined __HAIKU__
 #  include <ByteOrder.h>
 # else
 #  include <arpa/inet.h>
 # endif
 # include <inttypes.h>
 #endif
 
 static PyObject *parse_dirstate(PyObject *self, PyObject *args)
 {
 	PyObject *dmap, *cmap, *parents = NULL, *ret = NULL;
 	PyObject *fname = NULL, *cname = NULL, *entry = NULL;
 	char *str, *cur, *end, *cpos;
 	int state, mode, size, mtime, flen;
 	int len;
 	char decode[16]; /* for alignment */
 
 	if (!PyArg_ParseTuple(args, "O!O!s#:parse_dirstate",
 			      &PyDict_Type, &dmap,
 			      &PyDict_Type, &cmap,
 			      &str, &len))
 		goto quit;
 
 	/* read parents */
 	if (len < 40)
 		goto quit;
 
 	parents = Py_BuildValue("s#s#", str, 20, str + 20, 20);
 	if (!parents)
 		goto quit;
 
 	/* read filenames */
 	cur = str + 40;
 	end = str + len;
 
 	while (cur < end - 17) {
 		/* unpack header */
 		state = *cur;
 		memcpy(decode, cur + 1, 16);
 		mode = ntohl(*(uint32_t *)(decode));
 		size = ntohl(*(uint32_t *)(decode + 4));
 		mtime = ntohl(*(uint32_t *)(decode + 8));
 		flen = ntohl(*(uint32_t *)(decode + 12));
 		cur += 17;
 		if (cur + flen > end)
 			goto quit;
 
 		entry = Py_BuildValue("ciii", state, mode, size, mtime);
 		PyObject_GC_UnTrack(entry); /* don't waste time with this */
 		if (!entry)
 			goto quit;
 
 		cpos = memchr(cur, 0, flen);
 		if (cpos) {
 			fname = PyString_FromStringAndSize(cur, cpos - cur);
 			cname = PyString_FromStringAndSize(cpos + 1,
 							   flen - (cpos - cur) - 1);
 			if (!fname || !cname ||
 			    PyDict_SetItem(cmap, fname, cname) == -1 ||
 			    PyDict_SetItem(dmap, fname, entry) == -1)
 				goto quit;
 			Py_DECREF(cname);
 		} else {
 			fname = PyString_FromStringAndSize(cur, flen);
 			if (!fname ||
 			    PyDict_SetItem(dmap, fname, entry) == -1)
 				goto quit;
 		}
 		cur += flen;
 		Py_DECREF(fname);
 		Py_DECREF(entry);
 		fname = cname = entry = NULL;
 	}
 
 	ret = parents;
 	Py_INCREF(ret);
 quit:
 	Py_XDECREF(fname);
 	Py_XDECREF(cname);
 	Py_XDECREF(entry);
 	Py_XDECREF(parents);
 	return ret;
 }
 
 const char nullid[20];
 const int nullrev = -1;
 
+/* create an index tuple, insert into the nodemap */
+static PyObject * _build_idx_entry(PyObject *nodemap, int n, uint64_t offset_flags,
+                                   int comp_len, int uncomp_len, int base_rev,
+                                   int link_rev, int parent_1, int parent_2,
+                                   const char *c_node_id)
+{
+	int err;
+	PyObject *entry, *node_id, *n_obj;
+
+	node_id = PyString_FromStringAndSize(c_node_id, 20);
+	n_obj = PyInt_FromLong(n);
+	if (!node_id || !n_obj)
+		err = -1;
+	else
+		err = PyDict_SetItem(nodemap, node_id, n_obj);
+
+	Py_XDECREF(n_obj);
+	if (err)
+		goto error_dealloc;
+
+	entry = Py_BuildValue("LiiiiiiN", offset_flags, comp_len,
+			      uncomp_len, base_rev, link_rev,
+			      parent_1, parent_2, node_id);
+	if (!entry)
+		goto error_dealloc;
+	PyObject_GC_UnTrack(entry); /* don't waste time with this */
+
+	return entry;
+
+error_dealloc:
+	Py_XDECREF(node_id);
+	return NULL;
+}
+
 /* RevlogNG format (all in big endian, data may be inlined):
  *    6 bytes: offset
  *    2 bytes: flags
  *    4 bytes: compressed length
  *    4 bytes: uncompressed length
  *    4 bytes: base revision
  *    4 bytes: link revision
  *    4 bytes: parent 1 revision
  *    4 bytes: parent 2 revision
  *   32 bytes: nodeid (only 20 bytes used)
  */
 static int _parse_index_ng (const char *data, int size, int inlined,
 			    PyObject *index, PyObject *nodemap)
 {
-	PyObject *entry = NULL, *node_id = NULL, *n_obj = NULL;
-	PyObject *nullrev_obj = NULL, *nullid_obj = NULL;
+	PyObject *entry;
+	int n = 0, err;
+	uint64_t offset_flags;
 	int comp_len, uncomp_len, base_rev, link_rev, parent_1, parent_2;
-	uint64_t offset_flags;
-	int n = 0;
+	const char *c_node_id;
 	const char *end = data + size;
 
 	while (data < end) {
                 offset_flags = ntohl(*((uint32_t *) (data + 4)));
                 if (n == 0) /* mask out version number for the first entry */
                         offset_flags &= 0xFFFF;
                 else {
 			uint32_t offset_high =  ntohl(*((uint32_t *) data));
                         offset_flags |= ((uint64_t) offset_high) << 32;
 		}
 
-
 		comp_len = ntohl(*((uint32_t *) (data + 8)));
 		uncomp_len = ntohl(*((uint32_t *) (data + 12)));
 		base_rev = ntohl(*((uint32_t *) (data + 16)));
 		link_rev = ntohl(*((uint32_t *) (data + 20)));
 		parent_1 = ntohl(*((uint32_t *) (data + 24)));
 		parent_2 = ntohl(*((uint32_t *) (data + 28)));
-		node_id = PyString_FromStringAndSize(data + 32, 20);
-		n_obj = PyInt_FromLong(n);
-		if (!node_id || !n_obj ||
-		    PyDict_SetItem(nodemap, node_id, n_obj) != 0)
-			goto quit;
-		Py_DECREF(n_obj);
+		c_node_id = data + 32;
 		
-		entry = Py_BuildValue("LiiiiiiN", offset_flags, comp_len,
-				      uncomp_len, base_rev, link_rev,
-				      parent_1, parent_2, node_id);
-		PyObject_GC_UnTrack(entry); /* don't waste time with this */
+		entry = _build_idx_entry(nodemap, n, offset_flags,
+					comp_len, uncomp_len, base_rev,
+					link_rev, parent_1, parent_2,
+					c_node_id);
 		if (!entry)
-			goto quit;
+			return 0;
 
-		/* append to or set value in the index list */
 		if (inlined) {
-			if (PyList_Append(index, entry) != 0)
-				goto quit;
+			err = PyList_Append(index, entry);
 			Py_DECREF(entry);
-		} else {
+			if (err)
+				return 0;
+		} else
 			PyList_SET_ITEM(index, n, entry); /* steals reference */
-		}
 
 		data += 64 + (inlined ? comp_len : 0);
 		n++;
 	}
 	if (data > end) {
 		if (!PyErr_Occurred())
 			PyErr_SetString(PyExc_ValueError, "corrupt index file");
-		goto quit;
+		return 0;
 	}
 
 	/* create the nullid/nullrev entry in the nodemap and the 
 	 * magic nullid entry in the index at [-1] */
-	nullid_obj = PyString_FromStringAndSize(nullid, 20);
-	nullrev_obj = PyInt_FromLong(nullrev);
-	if (!nodemap || !nullid_obj || !nullrev_obj ||
-	    PyDict_SetItem(nodemap, nullid_obj, nullrev_obj) != 0)
-		goto quit;
-	Py_DECREF(nullrev_obj);
-		
-	entry = Py_BuildValue("iiiiiiiN", 0, 0, 0, -1, -1, -1, -1, nullid_obj);
-	PyObject_GC_UnTrack(entry); /* don't waste time with this */
+	entry = _build_idx_entry(nodemap, 
+			nullrev, 0, 0, 0, -1, -1, -1, -1, nullid);
 	if (!entry)
-		goto quit;
+		return 0;
 	if (inlined) {
-		if (PyList_Append(index, entry) != 0)
-			goto quit;
+		err = PyList_Append(index, entry);
 		Py_DECREF(entry);
-	} else {
+		if (err)
+			return 0;
+	} else
 		PyList_SET_ITEM(index, n, entry); /* steals reference */
-	}
 
 	return 1;
-
-quit:
-	Py_XDECREF(n_obj);
-	Py_XDECREF(node_id);
-	Py_XDECREF(entry);
-	Py_XDECREF(nullrev_obj);
-	Py_XDECREF(nullid_obj);
-	return 0;
 }
 
-
-
 /* This function parses a index file and returns a Python tuple of the
  * following format: (index, nodemap, cache)
  *
  * index: a list of tuples containing the RevlogNG records
  * nodemap: a dict mapping node ids to indices in the index list
  * cache: if data is inlined, a tuple (index_file_content, 0) else None
  */
 static PyObject *parse_index(PyObject *self, PyObject *args)
 {
 	const char *data;
 	int size, inlined;
 	PyObject *rval = NULL, *index = NULL, *nodemap = NULL, *cache = NULL; 
 	PyObject *data_obj = NULL, *inlined_obj;
 
 	if (!PyArg_ParseTuple(args, "s#O", &data, &size, &inlined_obj))
 		return NULL;
 	inlined = inlined_obj && PyObject_IsTrue(inlined_obj);
 
 	/* If no data is inlined, we know the size of the index list in 
 	 * advance: size divided by size of one one revlog record (64 bytes) 
 	 * plus one for the nullid */  
 	index = inlined ? PyList_New(0) : PyList_New(size / 64 + 1);
 	if (!index)
 		goto quit;
 
 	nodemap = PyDict_New();
+	if (!nodemap)
+		goto quit;
 
 	/* set up the cache return value */
 	if (inlined) {
 		/* Note that the reference to data_obj is only borrowed */
 		data_obj = PyTuple_GET_ITEM(args, 0);
 		cache = Py_BuildValue("iO", 0, data_obj);
 		if (!cache)
 			goto quit;
 	} else {
 		cache = Py_None;
 		Py_INCREF(Py_None);
 	}
 
 	/* actually populate the index and the nodemap with data */
 	if (!_parse_index_ng (data, size, inlined, index, nodemap))
 		goto quit;
 
 	rval = Py_BuildValue("NNN", index, nodemap, cache);
 	if (!rval)
 		goto quit;
 	return rval;
 
 quit:
 	Py_XDECREF(index);
 	Py_XDECREF(nodemap);
 	Py_XDECREF(cache);
 	Py_XDECREF(rval);
 	Py_XDECREF(data_obj);
 	return NULL;
 }
 
 
 static char parsers_doc[] = "Efficient content parsing.";
 
 static PyMethodDef methods[] = {
 	{"parse_manifest", parse_manifest, METH_VARARGS, "parse a manifest\n"},
 	{"parse_dirstate", parse_dirstate, METH_VARARGS, "parse a dirstate\n"},
 	{"parse_index", parse_index, METH_VARARGS, "parse a revlog index\n"},
 	{NULL, NULL}
 };
 
 PyMODINIT_FUNC initparsers(void)
 {
 	Py_InitModule3("parsers", methods, parsers_doc);
 }