The regular expression engine in '_sre' can segfault when interpreting

bogus bytecode.  It is unclear whether this is a real bug or a "won't
fix" case like bogus_code_obj.py.

Lib/test/crashers/bogus_sre_bytecode.py

@@ -0,0 +1,47 @@
+"""
+The regular expression engine in '_sre' can segfault when interpreting
+bogus bytecode.
+
+It is unclear whether this is a real bug or a "won't fix" case like
+bogus_code_obj.py, because it requires bytecode that is built by hand,
+as opposed to compiled by 're' from a string-source regexp.  The
+difference with bogus_code_obj, though, is that the only existing regexp
+compiler is written in Python, so that the C code has no choice but
+accept arbitrary bytecode from Python-level.
+
+The test below builds and runs random bytecodes until 'match' crashes
+Python.  I have not investigated why exactly segfaults occur nor how
+hard they would be to fix.  Here are a few examples of 'code' that
+segfault for me:
+
+    [21, 50814, 8, 29, 16]
+    [21, 3967, 26, 10, 23, 54113]
+    [29, 23, 0, 2, 5]
+    [31, 64351, 0, 28, 3, 22281, 20, 4463, 9, 25, 59154, 15245, 2,
+                  16343, 3, 11600, 24380, 10, 37556, 10, 31, 15, 31]
+
+Here is also a 'code' that triggers an infinite uninterruptible loop:
+
+    [29, 1, 8, 21, 1, 43083, 6]
+
+"""
+
+import _sre, random
+
+def pick():
+    n = random.randrange(-65536, 65536)
+    if n < 0:
+        n &= 31
+    return n
+
+ss = ["", "world", "x" * 500]
+
+while 1:
+    code = [pick() for i in range(random.randrange(5, 25))]
+    print code
+    pat = _sre.compile(None, 0, code)
+    for s in ss:
+        try:
+            pat.match(s)
+        except RuntimeError:
+            pass