https://github.com/python/cpython/commit/813bc5694bd8aa43165468c5ea1dc27af973611d
commit: 813bc5694bd8aa43165468c5ea1dc27af973611d
branch: main
author: Neil Schemenauer <nas-git...@arctrix.com>
committer: nascheme <nas-git...@arctrix.com>
date: 2025-03-03T19:00:50-08:00
summary:
gh-130599: use static constants str-to-int conversion (gh-130714)
Avoid a data race in free-threaded builds due to mutating global arrays at
runtime. Instead, compute the constants with an external Python script and
then define them as static global constant arrays. These constants are
used by `long_from_non_binary_base()`.
files:
A Tools/scripts/long_conv_tables.py
M Objects/longobject.c
M Tools/c-analyzer/cpython/ignored.tsv
diff --git a/Objects/longobject.c b/Objects/longobject.c
index 370328dcfe8c9a..ab5cfab74d8a34 100644
--- a/Objects/longobject.c
+++ b/Objects/longobject.c
@@ -2820,6 +2820,58 @@ that triggers it(!). Instead the code was tested by
artificially allocating
just 1 digit at the start, so that the copying code was exercised for every
digit beyond the first.
***/
+
+// Tables are computed by Tools/scripts/long_conv_tables.py
+#if PYLONG_BITS_IN_DIGIT == 15
+ static const double log_base_BASE[37] = {0.0, 0.0, 0.0,
+ 0.10566416671474375, 0.0, 0.15479520632582416,
+ 0.17233083338141042, 0.18715699480384027, 0.0,
+ 0.2113283334294875, 0.22146187299249084, 0.23062877457581984,
+ 0.2389975000480771, 0.24669598120940617, 0.25382366147050694,
+ 0.26045937304056793, 0.0, 0.27249752275002265,
+ 0.27799500009615413, 0.2831951675629057, 0.28812853965915747,
+ 0.29282116151858406, 0.2972954412424865, 0.3015707970704675,
+ 0.3056641667147438, 0.30959041265164833, 0.3133626478760728,
+ 0.31699250014423125, 0.3204903281371736, 0.3238653996751715,
+ 0.3271260397072346, 0.3302797540257917, 0.0,
+ 0.3362929412905636, 0.3391641894166893, 0.34195220112966446,
+ 0.34466166676282084};
+ static const int convwidth_base[37] = {0, 0, 0, 9, 0, 6, 5, 5, 0,
+ 4, 4, 4, 4, 4, 3, 3, 0, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
+ 3, 3, 0, 2, 2, 2, 2};
+ static const twodigits convmultmax_base[37] = {0, 0, 0, 19683, 0,
+ 15625, 7776, 16807, 0, 6561, 10000, 14641, 20736, 28561, 2744,
+ 3375, 0, 4913, 5832, 6859, 8000, 9261, 10648, 12167, 13824,
+ 15625, 17576, 19683, 21952, 24389, 27000, 29791, 0, 1089,
+ 1156, 1225, 1296};
+#elif PYLONG_BITS_IN_DIGIT == 30
+ static const double log_base_BASE[37] = {0.0, 0.0, 0.0,
+ 0.05283208335737188, 0.0, 0.07739760316291208,
+ 0.08616541669070521, 0.09357849740192013, 0.0,
+ 0.10566416671474375, 0.11073093649624542, 0.11531438728790992,
+ 0.11949875002403855, 0.12334799060470308, 0.12691183073525347,
+ 0.13022968652028397, 0.0, 0.13624876137501132,
+ 0.13899750004807707, 0.14159758378145285, 0.14406426982957873,
+ 0.14641058075929203, 0.14864772062124326, 0.15078539853523376,
+ 0.1528320833573719, 0.15479520632582416, 0.1566813239380364,
+ 0.15849625007211562, 0.1602451640685868, 0.16193269983758574,
+ 0.1635630198536173, 0.16513987701289584, 0.0,
+ 0.1681464706452818, 0.16958209470834465, 0.17097610056483223,
+ 0.17233083338141042};
+ static const int convwidth_base[37] = {0, 0, 0, 18, 0, 12, 11, 10,
+ 0, 9, 9, 8, 8, 8, 7, 7, 0, 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 6,
+ 6, 6, 6, 0, 5, 5, 5, 5};
+ static const twodigits convmultmax_base[37] = {0, 0, 0, 387420489,
+ 0, 244140625, 362797056, 282475249, 0, 387420489, 1000000000,
+ 214358881, 429981696, 815730721, 105413504, 170859375, 0,
+ 410338673, 612220032, 893871739, 64000000, 85766121,
+ 113379904, 148035889, 191102976, 244140625, 308915776,
+ 387420489, 481890304, 594823321, 729000000, 887503681, 0,
+ 39135393, 45435424, 52521875, 60466176};
+#else
+ #error "invalid PYLONG_BITS_IN_DIGIT value"
+#endif
+
static int
long_from_non_binary_base(const char *start, const char *end, Py_ssize_t
digits, int base, PyLongObject **res)
{
@@ -2832,28 +2884,7 @@ long_from_non_binary_base(const char *start, const char
*end, Py_ssize_t digits,
PyLongObject *z;
const char *p;
- static double log_base_BASE[37] = {0.0e0,};
- static int convwidth_base[37] = {0,};
- static twodigits convmultmax_base[37] = {0,};
-
- if (log_base_BASE[base] == 0.0) {
- twodigits convmax = base;
- int i = 1;
-
- log_base_BASE[base] = (log((double)base) /
- log((double)PyLong_BASE));
- for (;;) {
- twodigits next = convmax * base;
- if (next > PyLong_BASE) {
- break;
- }
- convmax = next;
- ++i;
- }
- convmultmax_base[base] = convmax;
- assert(i > 0);
- convwidth_base[base] = i;
- }
+ assert(log_base_BASE[base] != 0.0);
/* Create an int object that can contain the largest possible
* integer with this base and length. Note that there's no
diff --git a/Tools/c-analyzer/cpython/ignored.tsv
b/Tools/c-analyzer/cpython/ignored.tsv
index df0262f9c84148..9b624d809879ff 100644
--- a/Tools/c-analyzer/cpython/ignored.tsv
+++ b/Tools/c-analyzer/cpython/ignored.tsv
@@ -28,11 +28,13 @@ Python/thread_pthread.h PyThread__init_thread
lib_initialized -
##-----------------------
## other values (not Python-specific)
+# static tables computed by external script
+Objects/longobject.c - log_base_BASE -
+Objects/longobject.c - convwidth_base -
+Objects/longobject.c - convmultmax_base -
+
## cached computed data - set lazily (*after* first init)
# XXX Are these safe relative to write races?
-Objects/longobject.c long_from_non_binary_base log_base_BASE -
-Objects/longobject.c long_from_non_binary_base convwidth_base -
-Objects/longobject.c long_from_non_binary_base convmultmax_base
-
Objects/unicodeobject.c - bloom_linebreak -
# This is safe:
Objects/unicodeobject.c _init_global_state initialized -
diff --git a/Tools/scripts/long_conv_tables.py
b/Tools/scripts/long_conv_tables.py
new file mode 100644
index 00000000000000..998a1e0d9b2251
--- /dev/null
+++ b/Tools/scripts/long_conv_tables.py
@@ -0,0 +1,75 @@
+#!/usr/bin/env python3
+#
+# Compute tables for longobject.c long_from_non_binary_base(). They are used
+# for conversions of strings to integers with a non-binary base.
+
+import math
+import textwrap
+
+
+def format_array(name, values):
+ values = [str(v) for v in values]
+ values = ', '.join(values)
+ result = f'{name} = {{{values}}};'
+ result = textwrap.wrap(
+ result,
+ initial_indent=' ' * 4,
+ subsequent_indent=' ' * 8,
+ )
+ return '\n'.join(result)
+
+
+def conv_tables(long_bits):
+ PyLong_BASE = 1 << long_bits
+ log_base_BASE = [0.0] * 37
+ convmultmax_base = [0] * 37
+ convwidth_base = [0] * 37
+ for base in range(2, 37):
+ is_binary_base = (base & (base - 1)) == 0
+ if is_binary_base:
+ continue # don't need, leave as zero
+ convmax = base
+ i = 1
+ log_base_BASE[base] = math.log(base) / math.log(PyLong_BASE)
+ while True:
+ next = convmax * base
+ if next > PyLong_BASE:
+ break
+ convmax = next
+ i += 1
+ convmultmax_base[base] = convmax
+ assert i > 0
+ convwidth_base[base] = i
+ return '\n'.join(
+ [
+ format_array(
+ 'static const double log_base_BASE[37]', log_base_BASE
+ ),
+ format_array(
+ 'static const int convwidth_base[37]', convwidth_base
+ ),
+ format_array(
+ 'static const twodigits convmultmax_base[37]',
+ convmultmax_base,
+ ),
+ ]
+ )
+
+
+def main():
+ print(
+ f'''\
+// Tables are computed by Tools/scripts/long_conv_tables.py
+#if PYLONG_BITS_IN_DIGIT == 15
+{conv_tables(15)}
+#elif PYLONG_BITS_IN_DIGIT == 30
+{conv_tables(30)}
+#else
+ #error "invalid PYLONG_BITS_IN_DIGIT value"
+#endif
+'''
+ )
+
+
+if __name__ == '__main__':
+ main()
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