1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
|
/* Parse tree node implementation */
#include "Python.h"
#include "node.h"
#include "errcode.h"
node *
PyNode_New(int type)
{
node *n = (node *) PyObject_MALLOC(1 * sizeof(node));
if (n == NULL)
return NULL;
n->n_type = type;
n->n_str = NULL;
n->n_lineno = 0;
n->n_end_lineno = 0;
n->n_end_col_offset = -1;
n->n_nchildren = 0;
n->n_child = NULL;
return n;
}
/* See comments at XXXROUNDUP below. Returns -1 on overflow. */
static int
fancy_roundup(int n)
{
/* Round up to the closest power of 2 >= n. */
int result = 256;
assert(n > 128);
while (result < n) {
result <<= 1;
if (result <= 0)
return -1;
}
return result;
}
/* A gimmick to make massive numbers of reallocs quicker. The result is
* a number >= the input. In PyNode_AddChild, it's used like so, when
* we're about to add child number current_size + 1:
*
* if XXXROUNDUP(current_size) < XXXROUNDUP(current_size + 1):
* allocate space for XXXROUNDUP(current_size + 1) total children
* else:
* we already have enough space
*
* Since a node starts out empty, we must have
*
* XXXROUNDUP(0) < XXXROUNDUP(1)
*
* so that we allocate space for the first child. One-child nodes are very
* common (presumably that would change if we used a more abstract form
* of syntax tree), so to avoid wasting memory it's desirable that
* XXXROUNDUP(1) == 1. That in turn forces XXXROUNDUP(0) == 0.
*
* Else for 2 <= n <= 128, we round up to the closest multiple of 4. Why 4?
* Rounding up to a multiple of an exact power of 2 is very efficient, and
* most nodes with more than one child have <= 4 kids.
*
* Else we call fancy_roundup() to grow proportionately to n. We've got an
* extreme case then (like test_longexp.py), and on many platforms doing
* anything less than proportional growth leads to exorbitant runtime
* (e.g., MacPython), or extreme fragmentation of user address space (e.g.,
* Win98).
*
* In a run of compileall across the 2.3a0 Lib directory, Andrew MacIntyre
* reported that, with this scheme, 89% of PyObject_REALLOC calls in
* PyNode_AddChild passed 1 for the size, and 9% passed 4. So this usually
* wastes very little memory, but is very effective at sidestepping
* platform-realloc disasters on vulnerable platforms.
*
* Note that this would be straightforward if a node stored its current
* capacity. The code is tricky to avoid that.
*/
#define XXXROUNDUP(n) ((n) <= 1 ? (n) : \
(n) <= 128 ? (int)_Py_SIZE_ROUND_UP((n), 4) : \
fancy_roundup(n))
void
_PyNode_FinalizeEndPos(node *n)
{
int nch = NCH(n);
node *last;
if (nch == 0) {
return;
}
last = CHILD(n, nch - 1);
_PyNode_FinalizeEndPos(last);
n->n_end_lineno = last->n_end_lineno;
n->n_end_col_offset = last->n_end_col_offset;
}
int
PyNode_AddChild(node *n1, int type, char *str, int lineno, int col_offset,
int end_lineno, int end_col_offset)
{
const int nch = n1->n_nchildren;
int current_capacity;
int required_capacity;
node *n;
// finalize end position of previous node (if any)
if (nch > 0) {
_PyNode_FinalizeEndPos(CHILD(n1, nch - 1));
}
if (nch == INT_MAX || nch < 0)
return E_OVERFLOW;
current_capacity = XXXROUNDUP(nch);
required_capacity = XXXROUNDUP(nch + 1);
if (current_capacity < 0 || required_capacity < 0)
return E_OVERFLOW;
if (current_capacity < required_capacity) {
if ((size_t)required_capacity > SIZE_MAX / sizeof(node)) {
return E_NOMEM;
}
n = n1->n_child;
n = (node *) PyObject_REALLOC(n,
required_capacity * sizeof(node));
if (n == NULL)
return E_NOMEM;
n1->n_child = n;
}
n = &n1->n_child[n1->n_nchildren++];
n->n_type = type;
n->n_str = str;
n->n_lineno = lineno;
n->n_col_offset = col_offset;
n->n_end_lineno = end_lineno; // this and below will be updates after all children are added.
n->n_end_col_offset = end_col_offset;
n->n_nchildren = 0;
n->n_child = NULL;
return 0;
}
/* Forward */
static void freechildren(node *);
static Py_ssize_t sizeofchildren(node *n);
void
PyNode_Free(node *n)
{
if (n != NULL) {
freechildren(n);
PyObject_FREE(n);
}
}
Py_ssize_t
_PyNode_SizeOf(node *n)
{
Py_ssize_t res = 0;
if (n != NULL)
res = sizeof(node) + sizeofchildren(n);
return res;
}
static void
freechildren(node *n)
{
int i;
for (i = NCH(n); --i >= 0; )
freechildren(CHILD(n, i));
if (n->n_child != NULL)
PyObject_FREE(n->n_child);
if (STR(n) != NULL)
PyObject_FREE(STR(n));
}
static Py_ssize_t
sizeofchildren(node *n)
{
Py_ssize_t res = 0;
int i;
for (i = NCH(n); --i >= 0; )
res += sizeofchildren(CHILD(n, i));
if (n->n_child != NULL)
/* allocated size of n->n_child array */
res += XXXROUNDUP(NCH(n)) * sizeof(node);
if (STR(n) != NULL)
res += strlen(STR(n)) + 1;
return res;
}
|
