diff --git a/Python/compile.c b/Python/compile.c
index c81218d..264fdcd 100644
--- a/Python/compile.c
+++ b/Python/compile.c
@@ -216,6 +216,10 @@
 		return ident; /* Don't mangle if class is just underscores */
 	}
 	plen = strlen(p);
+
+	assert(1 <= PY_SSIZE_T_MAX - nlen);
+	assert(1 + nlen <= PY_SSIZE_T_MAX - plen);
+
 	ident = PyString_FromStringAndSize(NULL, 1 + nlen + plen);
 	if (!ident)
 		return 0;
@@ -621,6 +625,12 @@
 		size_t oldsize, newsize;
 		oldsize = b->b_ialloc * sizeof(struct instr);
 		newsize = oldsize << 1;
+
+		if (oldsize > (PY_SIZE_MAX >> 1)) {
+			PyErr_NoMemory();
+			return -1;
+		}
+
 		if (newsize == 0) {
 			PyErr_NoMemory();
 			return -1;
@@ -3478,6 +3488,10 @@
 	a->a_lnotab = PyString_FromStringAndSize(NULL, DEFAULT_LNOTAB_SIZE);
 	if (!a->a_lnotab)
 		return 0;
+	if (nblocks > PY_SIZE_MAX / sizeof(basicblock *)) {
+		PyErr_NoMemory();
+		return 0;
+	}
 	a->a_postorder = (basicblock **)PyObject_Malloc(
 					    sizeof(basicblock *) * nblocks);
 	if (!a->a_postorder) {
@@ -3586,10 +3600,14 @@
 		nbytes = a->a_lnotab_off + 2 * ncodes;
 		len = PyString_GET_SIZE(a->a_lnotab);
 		if (nbytes >= len) {
-			if (len * 2 < nbytes)
+			if ((len <= INT_MAX / 2) && (len * 2 < nbytes))
 				len = nbytes;
-			else
+			else if (len <= INT_MAX / 2)
 				len *= 2;
+			else {
+				PyErr_NoMemory();
+				return 0;
+			}
 			if (_PyString_Resize(&a->a_lnotab, len) < 0)
 				return 0;
 		}
@@ -3608,10 +3626,14 @@
 		nbytes = a->a_lnotab_off + 2 * ncodes;
 		len = PyString_GET_SIZE(a->a_lnotab);
 		if (nbytes >= len) {
-			if (len * 2 < nbytes)
+			if ((len <= INT_MAX / 2) && len * 2 < nbytes)
 				len = nbytes;
-			else
+			else if (len <= INT_MAX / 2)
 				len *= 2;
+			else {
+				PyErr_NoMemory();
+				return 0;
+			}
 			if (_PyString_Resize(&a->a_lnotab, len) < 0)
 				return 0;
 		}
@@ -3670,6 +3692,8 @@
 	if (i->i_lineno && !assemble_lnotab(a, i))
 		return 0;
 	if (a->a_offset + size >= len) {
+		if (len > PY_SSIZE_T_MAX / 2)
+			return 0;
 		if (_PyString_Resize(&a->a_bytecode, len * 2) < 0)
 		    return 0;
 	}