| 1 | #!/usr/bin/env python2
|
| 2 | """
|
| 3 | gc_stack_roots.py
|
| 4 | """
|
| 5 | from __future__ import print_function
|
| 6 |
|
| 7 | import os
|
| 8 |
|
| 9 | from mycpp import mylib
|
| 10 | from mycpp.mylib import log
|
| 11 |
|
| 12 | from typing import Any, List
|
| 13 | """
|
| 14 | Helpers
|
| 15 | """
|
| 16 |
|
| 17 |
|
| 18 | def print_list(l):
|
| 19 | # type: (List[str]) -> None
|
| 20 | for s in l:
|
| 21 | print(s)
|
| 22 |
|
| 23 |
|
| 24 | def calls_collect():
|
| 25 | # type: () -> None
|
| 26 | mylib.MaybeCollect()
|
| 27 |
|
| 28 |
|
| 29 | def ignore_and_collect(l):
|
| 30 | # type: (List[str]) -> None
|
| 31 | mylib.MaybeCollect()
|
| 32 |
|
| 33 |
|
| 34 | def collect_and_return(l):
|
| 35 | # type: (List[str]) -> List[str]
|
| 36 | mylib.MaybeCollect()
|
| 37 | return l
|
| 38 |
|
| 39 |
|
| 40 | def collect_and_slice(s):
|
| 41 | # type: (str) -> str
|
| 42 | mylib.MaybeCollect()
|
| 43 | return s[1:]
|
| 44 |
|
| 45 |
|
| 46 | class ctx_Stasher(object):
|
| 47 |
|
| 48 | def __init__(self, l):
|
| 49 | # type: (List[str]) -> None
|
| 50 | self.l = l
|
| 51 |
|
| 52 | def __enter__(self):
|
| 53 | # type: () -> None
|
| 54 | pass
|
| 55 |
|
| 56 | def __exit__(self, type, value, traceback):
|
| 57 | # type: (Any, Any, Any) -> None
|
| 58 | print_list(self.l)
|
| 59 |
|
| 60 |
|
| 61 | """
|
| 62 | Test cases
|
| 63 | """
|
| 64 |
|
| 65 |
|
| 66 | def no_collect():
|
| 67 | # type: () -> None
|
| 68 | """
|
| 69 | There's no need to gernate any stack roots in this case. There is no threat
|
| 70 | of anything being swept.
|
| 71 | """
|
| 72 | l = ['no', 'collect'] # type: List[str]
|
| 73 | print_list(l)
|
| 74 |
|
| 75 |
|
| 76 | def simple_collect():
|
| 77 | # type: () -> None
|
| 78 | """
|
| 79 | Only l1 needs to be rooted here. l2 is not live after the call to collect.
|
| 80 | """
|
| 81 | l1 = ['foo', 'bar'] # type: List[str]
|
| 82 | l2 = ['bing', 'bong'] # type: List[str]
|
| 83 | print_list(l2)
|
| 84 | if len(l1):
|
| 85 | mylib.MaybeCollect()
|
| 86 |
|
| 87 | print_list(l1)
|
| 88 |
|
| 89 |
|
| 90 | def indirect_collect():
|
| 91 | # type: () -> None
|
| 92 | """
|
| 93 | l should be rooted since it is live after an indirect call to collect.
|
| 94 | """
|
| 95 | l = ['indirect', 'collect']
|
| 96 | calls_collect()
|
| 97 | print_list(l)
|
| 98 |
|
| 99 |
|
| 100 | def arg_roots():
|
| 101 | # type: () -> None
|
| 102 | """
|
| 103 | If a function might collect it should unconditionally root its arguments.
|
| 104 | It should root them even if it doesn't use them directly because we can't
|
| 105 | gaurantee that the caller will even have been able to root them, e.g. in the
|
| 106 | case of function composition or an arugment being constructed inline.
|
| 107 | """
|
| 108 | l1 = ['OK'] # Should be rooted by ignore_and_collect().
|
| 109 | ignore_and_collect(l1)
|
| 110 | print_list(l1)
|
| 111 |
|
| 112 | # The temporary list should be rooted by collect_and_return().
|
| 113 | l2 = collect_and_return(['not', 'swept'])
|
| 114 | print_list(l2)
|
| 115 |
|
| 116 |
|
| 117 | def alias():
|
| 118 | # type: () -> None
|
| 119 | """
|
| 120 | Only one of l1 and l2 needs to be rooted here. In this case we should choose
|
| 121 | l2 since it is live after the collector runs.
|
| 122 | """
|
| 123 | l1 = ['foo', 'bar'] # type: List[str]
|
| 124 | l2 = l1
|
| 125 | mylib.MaybeCollect()
|
| 126 | print_list(l2)
|
| 127 |
|
| 128 |
|
| 129 | def collect_scoped_resource():
|
| 130 | # type: () -> None
|
| 131 | """
|
| 132 | Similar to function arguments, members of context managers should be rooted
|
| 133 | by their constructors. However, unlike normal functions these constructors
|
| 134 | should do so even if they don't cause a collection. The caller might trigger
|
| 135 | garbage collection while the manager is still in scope and the members will
|
| 136 | get swept if they weren't already rooted further up in the call stack.
|
| 137 | """
|
| 138 | with ctx_Stasher(['context', 'member']) as ctx:
|
| 139 | mylib.MaybeCollect()
|
| 140 |
|
| 141 |
|
| 142 | def collect_in_loop():
|
| 143 | # type: () -> None
|
| 144 | """
|
| 145 | Temporary variables used in loops should be rooted if a collection might
|
| 146 | happen within the loop body.
|
| 147 | """
|
| 148 | for s in ['watch', 'out']:
|
| 149 | mylib.MaybeCollect()
|
| 150 | print(s)
|
| 151 |
|
| 152 |
|
| 153 | def collect_in_comprehension():
|
| 154 | # type: () -> None
|
| 155 | """
|
| 156 | Temporary variables used in list comprehensions should be rooted if a
|
| 157 | collection might happen.
|
| 158 | """
|
| 159 | l = ['%s' % collect_and_slice(s) for s in ['foo', 'bar']] # type: List[str]
|
| 160 | for s in l:
|
| 161 | print(s)
|
| 162 |
|
| 163 |
|
| 164 | def run_tests():
|
| 165 | # type: () -> None
|
| 166 | no_collect()
|
| 167 | simple_collect()
|
| 168 | indirect_collect()
|
| 169 | arg_roots()
|
| 170 | alias()
|
| 171 | collect_scoped_resource()
|
| 172 | # TODO: maybe move these two to invalid examples if we decide to disallow.
|
| 173 | #collect_in_loop()
|
| 174 | #collect_in_comprehension()
|
| 175 |
|
| 176 |
|
| 177 | def run_benchmarks():
|
| 178 | # type: () -> None
|
| 179 | pass
|
| 180 |
|
| 181 |
|
| 182 | if __name__ == '__main__':
|
| 183 | if os.getenv('BENCHMARK'):
|
| 184 | log('Benchmarking...')
|
| 185 | run_benchmarks()
|
| 186 | else:
|
| 187 | run_tests()
|