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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()`.
This commit is contained in:
Neil Schemenauer
GitHub
parent
bbf197913c
commit
813bc5694b
3 changed files with 133 additions and 25 deletions
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@ -2820,6 +2820,58 @@ that triggers it(!). Instead the code was tested by artificially allocating
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just 1 digit at the start, so that the copying code was exercised for every
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digit beyond the first.
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***/
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// Tables are computed by Tools/scripts/long_conv_tables.py
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#if PYLONG_BITS_IN_DIGIT == 15
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static const double log_base_BASE[37] = {0.0, 0.0, 0.0,
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0.10566416671474375, 0.0, 0.15479520632582416,
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0.17233083338141042, 0.18715699480384027, 0.0,
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0.2113283334294875, 0.22146187299249084, 0.23062877457581984,
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0.2389975000480771, 0.24669598120940617, 0.25382366147050694,
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0.26045937304056793, 0.0, 0.27249752275002265,
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0.27799500009615413, 0.2831951675629057, 0.28812853965915747,
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0.29282116151858406, 0.2972954412424865, 0.3015707970704675,
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0.3056641667147438, 0.30959041265164833, 0.3133626478760728,
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0.31699250014423125, 0.3204903281371736, 0.3238653996751715,
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0.3271260397072346, 0.3302797540257917, 0.0,
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0.3362929412905636, 0.3391641894166893, 0.34195220112966446,
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0.34466166676282084};
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static const int convwidth_base[37] = {0, 0, 0, 9, 0, 6, 5, 5, 0,
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4, 4, 4, 4, 4, 3, 3, 0, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3, 3,
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3, 3, 0, 2, 2, 2, 2};
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static const twodigits convmultmax_base[37] = {0, 0, 0, 19683, 0,
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15625, 7776, 16807, 0, 6561, 10000, 14641, 20736, 28561, 2744,
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3375, 0, 4913, 5832, 6859, 8000, 9261, 10648, 12167, 13824,
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15625, 17576, 19683, 21952, 24389, 27000, 29791, 0, 1089,
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1156, 1225, 1296};
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#elif PYLONG_BITS_IN_DIGIT == 30
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static const double log_base_BASE[37] = {0.0, 0.0, 0.0,
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0.05283208335737188, 0.0, 0.07739760316291208,
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0.08616541669070521, 0.09357849740192013, 0.0,
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0.10566416671474375, 0.11073093649624542, 0.11531438728790992,
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0.11949875002403855, 0.12334799060470308, 0.12691183073525347,
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0.13022968652028397, 0.0, 0.13624876137501132,
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0.13899750004807707, 0.14159758378145285, 0.14406426982957873,
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0.14641058075929203, 0.14864772062124326, 0.15078539853523376,
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0.1528320833573719, 0.15479520632582416, 0.1566813239380364,
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0.15849625007211562, 0.1602451640685868, 0.16193269983758574,
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0.1635630198536173, 0.16513987701289584, 0.0,
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0.1681464706452818, 0.16958209470834465, 0.17097610056483223,
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0.17233083338141042};
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static const int convwidth_base[37] = {0, 0, 0, 18, 0, 12, 11, 10,
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0, 9, 9, 8, 8, 8, 7, 7, 0, 7, 7, 7, 6, 6, 6, 6, 6, 6, 6, 6, 6,
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6, 6, 6, 0, 5, 5, 5, 5};
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static const twodigits convmultmax_base[37] = {0, 0, 0, 387420489,
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0, 244140625, 362797056, 282475249, 0, 387420489, 1000000000,
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214358881, 429981696, 815730721, 105413504, 170859375, 0,
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410338673, 612220032, 893871739, 64000000, 85766121,
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113379904, 148035889, 191102976, 244140625, 308915776,
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387420489, 481890304, 594823321, 729000000, 887503681, 0,
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39135393, 45435424, 52521875, 60466176};
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#else
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#error "invalid PYLONG_BITS_IN_DIGIT value"
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#endif
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static int
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long_from_non_binary_base(const char *start, const char *end, Py_ssize_t digits, int base, PyLongObject **res)
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{
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@ -2832,28 +2884,7 @@ long_from_non_binary_base(const char *start, const char *end, Py_ssize_t digits,
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PyLongObject *z;
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const char *p;
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static double log_base_BASE[37] = {0.0e0,};
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static int convwidth_base[37] = {0,};
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static twodigits convmultmax_base[37] = {0,};
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if (log_base_BASE[base] == 0.0) {
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twodigits convmax = base;
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int i = 1;
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log_base_BASE[base] = (log((double)base) /
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log((double)PyLong_BASE));
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for (;;) {
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twodigits next = convmax * base;
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if (next > PyLong_BASE) {
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break;
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}
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convmax = next;
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++i;
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}
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convmultmax_base[base] = convmax;
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assert(i > 0);
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convwidth_base[base] = i;
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}
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assert(log_base_BASE[base] != 0.0);
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/* Create an int object that can contain the largest possible
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* integer with this base and length. Note that there's no
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@ -28,11 +28,13 @@ Python/thread_pthread.h PyThread__init_thread lib_initialized -
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##-----------------------
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## other values (not Python-specific)
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# static tables computed by external script
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Objects/longobject.c - log_base_BASE -
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Objects/longobject.c - convwidth_base -
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Objects/longobject.c - convmultmax_base -
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## cached computed data - set lazily (*after* first init)
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# XXX Are these safe relative to write races?
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Objects/longobject.c long_from_non_binary_base log_base_BASE -
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Objects/longobject.c long_from_non_binary_base convwidth_base -
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Objects/longobject.c long_from_non_binary_base convmultmax_base -
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Objects/unicodeobject.c - bloom_linebreak -
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# This is safe:
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Objects/unicodeobject.c _init_global_state initialized -
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Can't render this file because it has a wrong number of fields in line 4.
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Tools/scripts/long_conv_tables.py
Normal file
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Tools/scripts/long_conv_tables.py
Normal file
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@ -0,0 +1,75 @@
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#!/usr/bin/env python3
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#
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# Compute tables for longobject.c long_from_non_binary_base(). They are used
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# for conversions of strings to integers with a non-binary base.
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import math
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import textwrap
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def format_array(name, values):
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values = [str(v) for v in values]
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values = ', '.join(values)
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result = f'{name} = {{{values}}};'
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result = textwrap.wrap(
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result,
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initial_indent=' ' * 4,
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subsequent_indent=' ' * 8,
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)
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return '\n'.join(result)
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def conv_tables(long_bits):
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PyLong_BASE = 1 << long_bits
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log_base_BASE = [0.0] * 37
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convmultmax_base = [0] * 37
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convwidth_base = [0] * 37
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for base in range(2, 37):
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is_binary_base = (base & (base - 1)) == 0
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if is_binary_base:
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continue # don't need, leave as zero
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convmax = base
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i = 1
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log_base_BASE[base] = math.log(base) / math.log(PyLong_BASE)
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while True:
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next = convmax * base
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if next > PyLong_BASE:
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break
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convmax = next
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i += 1
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convmultmax_base[base] = convmax
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assert i > 0
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convwidth_base[base] = i
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return '\n'.join(
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[
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format_array(
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'static const double log_base_BASE[37]', log_base_BASE
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),
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format_array(
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'static const int convwidth_base[37]', convwidth_base
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),
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format_array(
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'static const twodigits convmultmax_base[37]',
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convmultmax_base,
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),
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]
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)
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def main():
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print(
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f'''\
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// Tables are computed by Tools/scripts/long_conv_tables.py
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#if PYLONG_BITS_IN_DIGIT == 15
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{conv_tables(15)}
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#elif PYLONG_BITS_IN_DIGIT == 30
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{conv_tables(30)}
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#else
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#error "invalid PYLONG_BITS_IN_DIGIT value"
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#endif
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'''
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)
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if __name__ == '__main__':
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main()
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