diffhelpers: verify hline was created before using it

Found with cpychecker.

mercurial/diffhelpers.c

@@ -1,197 +1,199
 /*
  * diffhelpers.c - helper routines for mpatch
  *
  * Copyright 2007 Chris Mason <[e-mail]>
  *
  * This software may be used and distributed according to the terms
  * of the GNU General Public License v2, incorporated herein by reference.
  */
 
 #include <Python.h>
 #include <stdlib.h>
 #include <string.h>
 
 #include "util.h"
 
 static char diffhelpers_doc[] = "Efficient diff parsing";
 static PyObject *diffhelpers_Error;
 
 
 /* fixup the last lines of a and b when the patch has no newline at eof */
 static void _fix_newline(PyObject *hunk, PyObject *a, PyObject *b)
 {
 	Py_ssize_t hunksz = PyList_Size(hunk);
 	PyObject *s = PyList_GET_ITEM(hunk, hunksz-1);
 	char *l = PyBytes_AsString(s);
 	Py_ssize_t alen = PyList_Size(a);
 	Py_ssize_t blen = PyList_Size(b);
 	char c = l[0];
 	PyObject *hline;
 	Py_ssize_t sz = PyBytes_GET_SIZE(s);
 
 	if (sz > 1 && l[sz-2] == '\r')
 		/* tolerate CRLF in last line */
 		sz -= 1;
 
 	hline = PyBytes_FromStringAndSize(l, sz-1);
+	if (!hline) {
+		return NULL;
+	}
 
 	if (c == ' ' || c == '+') {
 		PyObject *rline = PyBytes_FromStringAndSize(l + 1, sz - 2);
 		PyList_SetItem(b, blen-1, rline);
 	}
 	if (c == ' ' || c == '-') {
 		Py_INCREF(hline);
 		PyList_SetItem(a, alen-1, hline);
 	}
 	PyList_SetItem(hunk, hunksz-1, hline);
 }
 
 /* python callable form of _fix_newline */
 static PyObject *
 fix_newline(PyObject *self, PyObject *args)
 {
 	PyObject *hunk, *a, *b;
 	if (!PyArg_ParseTuple(args, "OOO", &hunk, &a, &b))
 		return NULL;
 	_fix_newline(hunk, a, b);
 	return Py_BuildValue("l", 0);
 }
 
 #if (PY_VERSION_HEX < 0x02050000)
 static const char *addlines_format = "OOiiOO";
 #else
 static const char *addlines_format = "OOnnOO";
 #endif
 
 /*
  * read lines from fp into the hunk.  The hunk is parsed into two arrays
  * a and b.  a gets the old state of the text, b gets the new state
  * The control char from the hunk is saved when inserting into a, but not b
  * (for performance while deleting files)
  */
 static PyObject *
 addlines(PyObject *self, PyObject *args)
 {
 
 	PyObject *fp, *hunk, *a, *b, *x;
 	Py_ssize_t i;
 	Py_ssize_t lena, lenb;
 	Py_ssize_t num;
 	Py_ssize_t todoa, todob;
 	char *s, c;
 	PyObject *l;
 	if (!PyArg_ParseTuple(args, addlines_format,
 			      &fp, &hunk, &lena, &lenb, &a, &b))
 		return NULL;
 
 	while (1) {
 		todoa = lena - PyList_Size(a);
 		todob = lenb - PyList_Size(b);
 		num = todoa > todob ? todoa : todob;
 		if (num == 0)
 		    break;
 		for (i = 0; i < num; i++) {
 			x = PyFile_GetLine(fp, 0);
 			s = PyBytes_AsString(x);
 			c = *s;
 			if (strcmp(s, "\\ No newline at end of file\n") == 0) {
 				_fix_newline(hunk, a, b);
 				continue;
 			}
 			if (c == '\n') {
 				/* Some patches may be missing the control char
 				 * on empty lines. Supply a leading space. */
 				Py_DECREF(x);
 				x = PyBytes_FromString(" \n");
 			}
 			PyList_Append(hunk, x);
 			if (c == '+') {
 				l = PyBytes_FromString(s + 1);
 				PyList_Append(b, l);
 				Py_DECREF(l);
 			} else if (c == '-') {
 				PyList_Append(a, x);
 			} else {
 				l = PyBytes_FromString(s + 1);
 				PyList_Append(b, l);
 				Py_DECREF(l);
 				PyList_Append(a, x);
 			}
 			Py_DECREF(x);
 		}
 	}
 	return Py_BuildValue("l", 0);
 }
 
 /*
  * compare the lines in a with the lines in b.  a is assumed to have
  * a control char at the start of each line, this char is ignored in the
  * compare
  */
 static PyObject *
 testhunk(PyObject *self, PyObject *args)
 {
 
 	PyObject *a, *b;
 	long bstart;
 	Py_ssize_t alen, blen;
 	Py_ssize_t i;
 	char *sa, *sb;
 
 	if (!PyArg_ParseTuple(args, "OOl", &a, &b, &bstart))
 		return NULL;
 	alen = PyList_Size(a);
 	blen = PyList_Size(b);
 	if (alen > blen - bstart || bstart < 0) {
 		return Py_BuildValue("l", -1);
 	}
 	for (i = 0; i < alen; i++) {
 		sa = PyBytes_AsString(PyList_GET_ITEM(a, i));
 		sb = PyBytes_AsString(PyList_GET_ITEM(b, i + bstart));
 		if (strcmp(sa + 1, sb) != 0)
 			return Py_BuildValue("l", -1);
 	}
 	return Py_BuildValue("l", 0);
 }
 
 static PyMethodDef methods[] = {
 	{"addlines", addlines, METH_VARARGS, "add lines to a hunk\n"},
 	{"fix_newline", fix_newline, METH_VARARGS, "fixup newline counters\n"},
 	{"testhunk", testhunk, METH_VARARGS, "test lines in a hunk\n"},
 	{NULL, NULL}
 };
 
 #ifdef IS_PY3K
 static struct PyModuleDef diffhelpers_module = {
 	PyModuleDef_HEAD_INIT,
 	"diffhelpers",
 	diffhelpers_doc,
 	-1,
 	methods
 };
 
 PyMODINIT_FUNC PyInit_diffhelpers(void)
 {
 	PyObject *m;
 
 	m = PyModule_Create(&diffhelpers_module);
 	if (m == NULL)
 		return NULL;
 
 	diffhelpers_Error = PyErr_NewException("diffhelpers.diffhelpersError",
 											NULL, NULL);
 	Py_INCREF(diffhelpers_Error);
 	PyModule_AddObject(m, "diffhelpersError", diffhelpers_Error);
 
 	return m;
 }
 #else
 PyMODINIT_FUNC
 initdiffhelpers(void)
 {
 	Py_InitModule3("diffhelpers", methods, diffhelpers_doc);
 	diffhelpers_Error = PyErr_NewException("diffhelpers.diffhelpersError",
 	                                        NULL, NULL);
 }
 #endif
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