_compile(): raise an exception if downcasting to SRE_CODE

loses information:

    OverflowError: regular expression code size limit exceeded

Otherwise the compiled code is gibberish, possibly leading at
least to wrong results or (as reported on c.l.py) internal
sre errors at match time.

I'm not sure how to test this.  SRE_CODE is a 2-byte type on
my box, and it's easy to create a regexp that causes the new
exception to trigger here.  But it may be a 4-byte type on
other boxes, and creating a regexp large enough to trigger
problems there would be pretty crazy.

Bugfix candidate.

1 files changed, 40 insertions, 37 deletions

diff --git a/Modules/_sre.c b/Modules/_sre.c
index 4d9d1cd..3cc90d4 100644
--- a/Modules/_sre.c
+++ b/Modules/_sre.c
@@ -451,7 +451,7 @@ SRE_CHARSET(SRE_CODE* set, SRE_CODE ch)
                 if (ch < 256 && (set[ch >> 4] & (1 << (ch & 15))))
                     return ok;
                 set += 16;
-            } 
+            }
             else {
                 /* <CHARSET> <bitmap> (32 bits per code word) */
                 if (ch < 256 && (set[ch >> 5] & (1 << (ch & 31))))
@@ -492,7 +492,7 @@ SRE_CHARSET(SRE_CODE* set, SRE_CODE ch)
                 else
                     block = -1;
                 set += 64;
-                if (block >=0 && 
+                if (block >=0 &&
                     (set[block*8 + ((ch & 255)>>5)] & (1 << (ch & 31))))
                     return ok;
                 set += count*8;
@@ -568,7 +568,7 @@ SRE_COUNT(SRE_STATE* state, SRE_CODE* pattern, int maxcount)
         while (ptr < end && (SRE_CODE) *ptr != chr)
             ptr++;
         break;
-                
+
     case SRE_OP_NOT_LITERAL_IGNORE:
         /* repeated non-literal */
         chr = pattern[1];
@@ -644,7 +644,7 @@ SRE_INFO(SRE_STATE* state, SRE_CODE* pattern)
  * - Recursive SRE_MATCH() returned false, and will continue the
  *   outside 'for' loop: must be protected when breaking, since the next
  *   OP could potentially depend on lastmark;
- *   
+ *
  * - Recursive SRE_MATCH() returned false, and will be called again
  *   inside a local for/while loop: must be protected between each
  *   loop iteration, since the recursive SRE_MATCH() could do anything,
@@ -848,7 +848,7 @@ entrance:
                 /* state->lastmark is the highest valid index in the
                    state->mark array.  If it is increased by more than 1,
                    the intervening marks must be set to NULL to signal
-                   that these marks have not been encountered. */ 
+                   that these marks have not been encountered. */
                 int j = state->lastmark + 1;
                 while (j < i)
                     state->mark[j++] = NULL;
@@ -1065,9 +1065,9 @@ entrance:
                         RETURN_ON_ERROR(ret);
                         RETURN_SUCCESS;
                     }
-                    
+
                     LASTMARK_RESTORE();
-                    
+
                     ctx->ptr--;
                     ctx->count--;
                 }
@@ -1115,7 +1115,7 @@ entrance:
                 RETURN_ON_ERROR(ret);
                 DATA_LOOKUP_AT(SRE_MATCH_CONTEXT, ctx, ctx_pos);
                 if (ret < (int) ctx->pattern[1])
-                    /* didn't match minimum number of times */ 
+                    /* didn't match minimum number of times */
                     RETURN_FAILURE;
                 /* advance past minimum matches of repeat */
                 ctx->count = ret;
@@ -1546,7 +1546,6 @@ SRE_SEARCH(SRE_STATE* state, SRE_CODE* pattern)
                     }
                     break;
                 }
-                
             }
             ptr++;
         }
@@ -1601,7 +1600,7 @@ SRE_SEARCH(SRE_STATE* state, SRE_CODE* pattern)
 
     return status;
 }
-    
+
 LOCAL(int)
 SRE_LITERAL_TEMPLATE(SRE_CHAR* ptr, int len)
 {
@@ -1652,10 +1651,14 @@ _compile(PyObject* self_, PyObject* args)
 
     for (i = 0; i < n; i++) {
         PyObject *o = PyList_GET_ITEM(code, i);
-        if (PyInt_Check(o))
-            self->code[i] = (SRE_CODE) PyInt_AsLong(o);
-        else
-            self->code[i] = (SRE_CODE) PyLong_AsUnsignedLong(o);
+        unsigned long value = PyInt_Check(o) ? (unsigned long)PyInt_AsLong(o)
+                                              : PyLong_AsUnsignedLong(o);
+        self->code[i] = (SRE_CODE) value;
+        if ((unsigned long) self->code[i] != value) {
+            PyErr_SetString(PyExc_OverflowError,
+                            "regular expression code size limit exceeded");
+            break;
+        }
     }
 
     if (PyErr_Occurred()) {
@@ -1724,7 +1727,7 @@ getstring(PyObject* string, int* p_length, int* p_charsize)
     /* given a python object, return a data pointer, a length (in
        characters), and a character size.  return NULL if the object
        is not a string (or not compatible) */
-    
+
     PyBufferProcs *buffer;
     int size, bytes, charsize;
     void* ptr;
@@ -2203,7 +2206,7 @@ pattern_findall(PatternObject* self, PyObject* args, PyObject* kw)
     while (state.start <= state.end) {
 
         PyObject* item;
-        
+
         state_reset(&state);
 
         state.ptr = state.start;
@@ -2222,7 +2225,7 @@ pattern_findall(PatternObject* self, PyObject* args, PyObject* kw)
             pattern_error(status);
             goto error;
         }
-        
+
         /* don't bother to build a match object */
         switch (self->groups) {
         case 0:
@@ -2271,7 +2274,7 @@ error:
     Py_DECREF(list);
     state_fini(&state);
     return NULL;
-    
+
 }
 
 #if PY_VERSION_HEX >= 0x02020000
@@ -2349,7 +2352,7 @@ pattern_split(PatternObject* self, PyObject* args, PyObject* kw)
             pattern_error(status);
             goto error;
         }
-        
+
         if (state.start == state.ptr) {
             if (last == state.end)
                 break;
@@ -2405,7 +2408,7 @@ error:
     Py_DECREF(list);
     state_fini(&state);
     return NULL;
-    
+
 }
 
 static PyObject*
@@ -2496,7 +2499,7 @@ pattern_subx(PatternObject* self, PyObject* template, PyObject* string,
             pattern_error(status);
             goto error;
         }
-        
+
         b = STATE_OFFSET(&state, state.start);
         e = STATE_OFFSET(&state, state.ptr);
 
@@ -2542,7 +2545,7 @@ pattern_subx(PatternObject* self, PyObject* template, PyObject* string,
             if (status < 0)
                 goto error;
         }
-        
+
         i = e;
         n = n + 1;
 
@@ -2586,7 +2589,7 @@ error:
     state_fini(&state);
     Py_DECREF(filter);
     return NULL;
-    
+
 }
 
 static PyObject*
@@ -2626,7 +2629,7 @@ pattern_copy(PatternObject* self, PyObject* args)
 
     if (args != Py_None && !PyArg_ParseTuple(args, ":__copy__"))
         return NULL;
-    
+
     copy = PyObject_NEW_VAR(PatternObject, &Pattern_Type, self->codesize);
     if (!copy)
         return NULL;
@@ -2653,7 +2656,7 @@ pattern_deepcopy(PatternObject* self, PyObject* args)
 {
 #ifdef USE_BUILTIN_COPY
     PatternObject* copy;
-    
+
     PyObject* memo;
     if (!PyArg_ParseTuple(args, "O:__deepcopy__", &memo))
         return NULL;
@@ -2701,28 +2704,28 @@ PyDoc_STRVAR(pattern_finditer_doc,
 PyDoc_STRVAR(pattern_sub_doc,
 "sub(repl, string[, count = 0]) --> newstring\n\
     Return the string obtained by replacing the leftmost non-overlapping\n\
-    occurrences of pattern in string by the replacement repl."); 
+    occurrences of pattern in string by the replacement repl.");
 
 PyDoc_STRVAR(pattern_subn_doc,
 "subn(repl, string[, count = 0]) --> (newstring, number of subs)\n\
     Return the tuple (new_string, number_of_subs_made) found by replacing\n\
     the leftmost non-overlapping occurrences of pattern with the\n\
-    replacement repl."); 
+    replacement repl.");
 
 PyDoc_STRVAR(pattern_doc, "Compiled regular expression objects");
 
 static PyMethodDef pattern_methods[] = {
-    {"match", (PyCFunction) pattern_match, METH_VARARGS|METH_KEYWORDS, 
+    {"match", (PyCFunction) pattern_match, METH_VARARGS|METH_KEYWORDS,
 	pattern_match_doc},
-    {"search", (PyCFunction) pattern_search, METH_VARARGS|METH_KEYWORDS, 
+    {"search", (PyCFunction) pattern_search, METH_VARARGS|METH_KEYWORDS,
 	pattern_search_doc},
     {"sub", (PyCFunction) pattern_sub, METH_VARARGS|METH_KEYWORDS,
 	pattern_sub_doc},
     {"subn", (PyCFunction) pattern_subn, METH_VARARGS|METH_KEYWORDS,
 	pattern_subn_doc},
-    {"split", (PyCFunction) pattern_split, METH_VARARGS|METH_KEYWORDS, 
+    {"split", (PyCFunction) pattern_split, METH_VARARGS|METH_KEYWORDS,
 	pattern_split_doc},
-    {"findall", (PyCFunction) pattern_findall, METH_VARARGS|METH_KEYWORDS, 
+    {"findall", (PyCFunction) pattern_findall, METH_VARARGS|METH_KEYWORDS,
 	pattern_findall_doc},
 #if PY_VERSION_HEX >= 0x02020000
     {"finditer", (PyCFunction) pattern_finditer, METH_VARARGS,
@@ -2734,7 +2737,7 @@ static PyMethodDef pattern_methods[] = {
     {NULL, NULL}
 };
 
-static PyObject*  
+static PyObject*
 pattern_getattr(PatternObject* self, char* name)
 {
     PyObject* res;
@@ -3113,7 +3116,7 @@ match_copy(MatchObject* self, PyObject* args)
 #ifdef USE_BUILTIN_COPY
     MatchObject* copy;
     int slots, offset;
-    
+
     if (args != Py_None && !PyArg_ParseTuple(args, ":__copy__"))
         return NULL;
 
@@ -3146,7 +3149,7 @@ match_deepcopy(MatchObject* self, PyObject* args)
 {
 #ifdef USE_BUILTIN_COPY
     MatchObject* copy;
-    
+
     PyObject* memo;
     if (!PyArg_ParseTuple(args, "O:__deepcopy__", &memo))
         return NULL;
@@ -3181,7 +3184,7 @@ static PyMethodDef match_methods[] = {
     {NULL, NULL}
 };
 
-static PyObject*  
+static PyObject*
 match_getattr(MatchObject* self, char* name)
 {
     PyObject* res;
@@ -3337,7 +3340,7 @@ static PyMethodDef scanner_methods[] = {
     {NULL, NULL}
 };
 
-static PyObject*  
+static PyObject*
 scanner_getattr(ScannerObject* self, char* name)
 {
     PyObject* res;
@@ -3374,7 +3377,7 @@ static PyMethodDef _functions[] = {
     {NULL, NULL}
 };
 
-#if PY_VERSION_HEX < 0x02030000 
+#if PY_VERSION_HEX < 0x02030000
 DL_EXPORT(void) init_sre(void)
 #else
 PyMODINIT_FUNC init_sre(void)