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27
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1 /*
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2
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3 Reference Cycle Garbage Collection
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4 ==================================
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5
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6 Neil Schemenauer <nas@arctrix.com>
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7
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8 Based on a post on the python-dev list. Ideas from Guido van Rossum,
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9 Eric Tiedemann, and various others.
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10
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11 http://www.arctrix.com/nas/python/gc/
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12
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13 The following mailing list threads provide a historical perspective on
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14 the design of this module. Note that a fair amount of refinement has
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15 occurred since those discussions.
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16
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17 http://mail.python.org/pipermail/python-dev/2000-March/002385.html
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18 http://mail.python.org/pipermail/python-dev/2000-March/002434.html
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19 http://mail.python.org/pipermail/python-dev/2000-March/002497.html
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20
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21 For a highlevel view of the collection process, read the collect
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22 function.
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23
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24 */
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25
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26 #include "Python.h"
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27 #include "frameobject.h" /* for PyFrame_ClearFreeList */
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28
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29 /* Get an object's GC head */
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30 #define AS_GC(o) ((PyGC_Head *)(o)-1)
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31
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32 /* Get the object given the GC head */
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33 #define FROM_GC(g) ((PyObject *)(((PyGC_Head *)g)+1))
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34
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35 /*** Global GC state ***/
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36
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37 struct gc_generation {
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38 PyGC_Head head;
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39 int threshold; /* collection threshold */
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40 int count; /* count of allocations or collections of younger
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41 generations */
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42 };
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43
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44 #define NUM_GENERATIONS 3
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45 #define GEN_HEAD(n) (&generations[n].head)
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46
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47 /* linked lists of container objects */
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48 static struct gc_generation generations[NUM_GENERATIONS] = {
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49 /* PyGC_Head, threshold, count */
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50 {{{GEN_HEAD(0), GEN_HEAD(0), 0}}, 700, 0},
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51 {{{GEN_HEAD(1), GEN_HEAD(1), 0}}, 10, 0},
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52 {{{GEN_HEAD(2), GEN_HEAD(2), 0}}, 10, 0},
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53 };
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54
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55 PyGC_Head *_PyGC_generation0 = GEN_HEAD(0);
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56
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57 static int enabled = 1; /* automatic collection enabled? */
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58
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59 /* true if we are currently running the collector */
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60 static int collecting = 0;
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61
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62 /* list of uncollectable objects */
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63 static PyObject *garbage = NULL;
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64
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65 /* Python string to use if unhandled exception occurs */
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66 static PyObject *gc_str = NULL;
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67
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68 /* Python string used to look for __del__ attribute. */
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69 static PyObject *delstr = NULL;
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70
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71 /* This is the number of objects who survived the last full collection. It
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72 approximates the number of long lived objects tracked by the GC.
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73
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74 (by "full collection", we mean a collection of the oldest generation).
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75 */
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76 static Py_ssize_t long_lived_total = 0;
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77
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78 /* This is the number of objects who survived all "non-full" collections,
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79 and are awaiting to undergo a full collection for the first time.
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80
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81 */
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82 static Py_ssize_t long_lived_pending = 0;
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83
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84 /*
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85 NOTE: about the counting of long-lived objects.
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86
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87 To limit the cost of garbage collection, there are two strategies;
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88 - make each collection faster, e.g. by scanning fewer objects
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89 - do less collections
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90 This heuristic is about the latter strategy.
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91
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92 In addition to the various configurable thresholds, we only trigger a
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93 full collection if the ratio
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94 long_lived_pending / long_lived_total
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95 is above a given value (hardwired to 25%).
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96
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97 The reason is that, while "non-full" collections (i.e., collections of
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98 the young and middle generations) will always examine roughly the same
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99 number of objects -- determined by the aforementioned thresholds --,
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100 the cost of a full collection is proportional to the total number of
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101 long-lived objects, which is virtually unbounded.
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102
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103 Indeed, it has been remarked that doing a full collection every
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104 <constant number> of object creations entails a dramatic performance
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105 degradation in workloads which consist in creating and storing lots of
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106 long-lived objects (e.g. building a large list of GC-tracked objects would
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107 show quadratic performance, instead of linear as expected: see issue #4074).
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108
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109 Using the above ratio, instead, yields amortized linear performance in
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110 the total number of objects (the effect of which can be summarized
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111 thusly: "each full garbage collection is more and more costly as the
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112 number of objects grows, but we do fewer and fewer of them").
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113
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114 This heuristic was suggested by Martin von Löwis on python-dev in
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115 June 2008. His original analysis and proposal can be found at:
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116 http://mail.python.org/pipermail/python-dev/2008-June/080579.html
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117 */
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118
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119
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120 /* set for debugging information */
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121 #define DEBUG_STATS (1<<0) /* print collection statistics */
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122 #define DEBUG_COLLECTABLE (1<<1) /* print collectable objects */
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123 #define DEBUG_UNCOLLECTABLE (1<<2) /* print uncollectable objects */
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124 #define DEBUG_SAVEALL (1<<5) /* save all garbage in gc.garbage */
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125 #define DEBUG_LEAK DEBUG_COLLECTABLE | \
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126 DEBUG_UNCOLLECTABLE | \
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127 DEBUG_SAVEALL
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128 static int debug;
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129 static PyObject *tmod = NULL;
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130
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131 /*--------------------------------------------------------------------------
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132 gc_refs values.
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133
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134 Between collections, every gc'ed object has one of two gc_refs values:
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135
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136 GC_UNTRACKED
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137 The initial state; objects returned by PyObject_GC_Malloc are in this
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138 state. The object doesn't live in any generation list, and its
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139 tp_traverse slot must not be called.
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140
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141 GC_REACHABLE
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142 The object lives in some generation list, and its tp_traverse is safe to
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143 call. An object transitions to GC_REACHABLE when PyObject_GC_Track
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144 is called.
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145
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146 During a collection, gc_refs can temporarily take on other states:
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147
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148 >= 0
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149 At the start of a collection, update_refs() copies the true refcount
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150 to gc_refs, for each object in the generation being collected.
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151 subtract_refs() then adjusts gc_refs so that it equals the number of
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152 times an object is referenced directly from outside the generation
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153 being collected.
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154 gc_refs remains >= 0 throughout these steps.
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155
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156 GC_TENTATIVELY_UNREACHABLE
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157 move_unreachable() then moves objects not reachable (whether directly or
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158 indirectly) from outside the generation into an "unreachable" set.
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159 Objects that are found to be reachable have gc_refs set to GC_REACHABLE
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160 again. Objects that are found to be unreachable have gc_refs set to
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161 GC_TENTATIVELY_UNREACHABLE. It's "tentatively" because the pass doing
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162 this can't be sure until it ends, and GC_TENTATIVELY_UNREACHABLE may
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163 transition back to GC_REACHABLE.
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164
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165 Only objects with GC_TENTATIVELY_UNREACHABLE still set are candidates
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166 for collection. If it's decided not to collect such an object (e.g.,
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167 it has a __del__ method), its gc_refs is restored to GC_REACHABLE again.
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168 ----------------------------------------------------------------------------
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169 */
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170 #define GC_UNTRACKED _PyGC_REFS_UNTRACKED
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171 #define GC_REACHABLE _PyGC_REFS_REACHABLE
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172 #define GC_TENTATIVELY_UNREACHABLE _PyGC_REFS_TENTATIVELY_UNREACHABLE
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173
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174 #define IS_TRACKED(o) ((AS_GC(o))->gc.gc_refs != GC_UNTRACKED)
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175 #define IS_REACHABLE(o) ((AS_GC(o))->gc.gc_refs == GC_REACHABLE)
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176 #define IS_TENTATIVELY_UNREACHABLE(o) ( \
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177 (AS_GC(o))->gc.gc_refs == GC_TENTATIVELY_UNREACHABLE)
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178
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179 /*** list functions ***/
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180
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181 static void
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182 gc_list_init(PyGC_Head *list)
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183 {
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184 list->gc.gc_prev = list;
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185 list->gc.gc_next = list;
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186 }
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187
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188 static int
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189 gc_list_is_empty(PyGC_Head *list)
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190 {
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191 return (list->gc.gc_next == list);
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192 }
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193
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194 #if 0
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195 /* This became unused after gc_list_move() was introduced. */
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196 /* Append `node` to `list`. */
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197 static void
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198 gc_list_append(PyGC_Head *node, PyGC_Head *list)
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199 {
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200 node->gc.gc_next = list;
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201 node->gc.gc_prev = list->gc.gc_prev;
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202 node->gc.gc_prev->gc.gc_next = node;
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203 list->gc.gc_prev = node;
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204 }
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205 #endif
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206
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207 /* Remove `node` from the gc list it's currently in. */
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208 static void
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209 gc_list_remove(PyGC_Head *node)
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210 {
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211 node->gc.gc_prev->gc.gc_next = node->gc.gc_next;
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212 node->gc.gc_next->gc.gc_prev = node->gc.gc_prev;
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213 node->gc.gc_next = NULL; /* object is not currently tracked */
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214 }
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215
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216 /* Move `node` from the gc list it's currently in (which is not explicitly
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217 * named here) to the end of `list`. This is semantically the same as
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218 * gc_list_remove(node) followed by gc_list_append(node, list).
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219 */
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220 static void
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221 gc_list_move(PyGC_Head *node, PyGC_Head *list)
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222 {
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223 PyGC_Head *new_prev;
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224 PyGC_Head *current_prev = node->gc.gc_prev;
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225 PyGC_Head *current_next = node->gc.gc_next;
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226 /* Unlink from current list. */
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227 current_prev->gc.gc_next = current_next;
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228 current_next->gc.gc_prev = current_prev;
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229 /* Relink at end of new list. */
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230 new_prev = node->gc.gc_prev = list->gc.gc_prev;
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231 new_prev->gc.gc_next = list->gc.gc_prev = node;
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232 node->gc.gc_next = list;
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233 }
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234
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235 /* append list `from` onto list `to`; `from` becomes an empty list */
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236 static void
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237 gc_list_merge(PyGC_Head *from, PyGC_Head *to)
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238 {
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239 PyGC_Head *tail;
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240 assert(from != to);
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241 if (!gc_list_is_empty(from)) {
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242 tail = to->gc.gc_prev;
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243 tail->gc.gc_next = from->gc.gc_next;
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244 tail->gc.gc_next->gc.gc_prev = tail;
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245 to->gc.gc_prev = from->gc.gc_prev;
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246 to->gc.gc_prev->gc.gc_next = to;
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247 }
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248 gc_list_init(from);
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249 }
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250
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251 static Py_ssize_t
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252 gc_list_size(PyGC_Head *list)
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253 {
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254 PyGC_Head *gc;
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255 Py_ssize_t n = 0;
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256 for (gc = list->gc.gc_next; gc != list; gc = gc->gc.gc_next) {
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257 n++;
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258 }
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259 return n;
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260 }
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261
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262 /* Append objects in a GC list to a Python list.
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263 * Return 0 if all OK, < 0 if error (out of memory for list).
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264 */
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265 static int
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266 append_objects(PyObject *py_list, PyGC_Head *gc_list)
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267 {
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268 PyGC_Head *gc;
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269 for (gc = gc_list->gc.gc_next; gc != gc_list; gc = gc->gc.gc_next) {
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270 PyObject *op = FROM_GC(gc);
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271 if (op != py_list) {
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272 if (PyList_Append(py_list, op)) {
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273 return -1; /* exception */
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274 }
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275 }
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276 }
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277 return 0;
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278 }
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279
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280 /*** end of list stuff ***/
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281
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282
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283 /* Set all gc_refs = ob_refcnt. After this, gc_refs is > 0 for all objects
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284 * in containers, and is GC_REACHABLE for all tracked gc objects not in
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285 * containers.
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286 */
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287 static void
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288 update_refs(PyGC_Head *containers)
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289 {
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290 PyGC_Head *gc = containers->gc.gc_next;
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291 for (; gc != containers; gc = gc->gc.gc_next) {
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292 assert(gc->gc.gc_refs == GC_REACHABLE);
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293 gc->gc.gc_refs = Py_REFCNT(FROM_GC(gc));
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294 /* Python's cyclic gc should never see an incoming refcount
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295 * of 0: if something decref'ed to 0, it should have been
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296 * deallocated immediately at that time.
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297 * Possible cause (if the assert triggers): a tp_dealloc
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298 * routine left a gc-aware object tracked during its teardown
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299 * phase, and did something-- or allowed something to happen --
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300 * that called back into Python. gc can trigger then, and may
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301 * see the still-tracked dying object. Before this assert
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302 * was added, such mistakes went on to allow gc to try to
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303 * delete the object again. In a debug build, that caused
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304 * a mysterious segfault, when _Py_ForgetReference tried
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305 * to remove the object from the doubly-linked list of all
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306 * objects a second time. In a release build, an actual
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307 * double deallocation occurred, which leads to corruption
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308 * of the allocator's internal bookkeeping pointers. That's
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309 * so serious that maybe this should be a release-build
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310 * check instead of an assert?
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311 */
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312 assert(gc->gc.gc_refs != 0);
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313 }
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314 }
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315
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316 /* A traversal callback for subtract_refs. */
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317 static int
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318 visit_decref(PyObject *op, void *data)
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319 {
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320 assert(op != NULL);
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321 if (PyObject_IS_GC(op)) {
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322 PyGC_Head *gc = AS_GC(op);
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323 /* We're only interested in gc_refs for objects in the
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324 * generation being collected, which can be recognized
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325 * because only they have positive gc_refs.
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326 */
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327 assert(gc->gc.gc_refs != 0); /* else refcount was too small */
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328 if (gc->gc.gc_refs > 0)
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329 gc->gc.gc_refs--;
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330 }
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331 return 0;
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332 }
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333
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334 /* Subtract internal references from gc_refs. After this, gc_refs is >= 0
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335 * for all objects in containers, and is GC_REACHABLE for all tracked gc
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336 * objects not in containers. The ones with gc_refs > 0 are directly
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337 * reachable from outside containers, and so can't be collected.
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338 */
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339 static void
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340 subtract_refs(PyGC_Head *containers)
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341 {
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342 traverseproc traverse;
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343 PyGC_Head *gc = containers->gc.gc_next;
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344 for (; gc != containers; gc=gc->gc.gc_next) {
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345 traverse = Py_TYPE(FROM_GC(gc))->tp_traverse;
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346 (void) traverse(FROM_GC(gc),
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347 (visitproc)visit_decref,
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348 NULL);
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349 }
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350 }
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351
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352 /* A traversal callback for move_unreachable. */
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353 static int
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354 visit_reachable(PyObject *op, PyGC_Head *reachable)
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355 {
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356 if (PyObject_IS_GC(op)) {
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357 PyGC_Head *gc = AS_GC(op);
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358 const Py_ssize_t gc_refs = gc->gc.gc_refs;
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359
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360 if (gc_refs == 0) {
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361 /* This is in move_unreachable's 'young' list, but
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362 * the traversal hasn't yet gotten to it. All
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363 * we need to do is tell move_unreachable that it's
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364 * reachable.
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365 */
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366 gc->gc.gc_refs = 1;
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367 }
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368 else if (gc_refs == GC_TENTATIVELY_UNREACHABLE) {
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369 /* This had gc_refs = 0 when move_unreachable got
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370 * to it, but turns out it's reachable after all.
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371 * Move it back to move_unreachable's 'young' list,
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372 * and move_unreachable will eventually get to it
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373 * again.
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374 */
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375 gc_list_move(gc, reachable);
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376 gc->gc.gc_refs = 1;
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377 }
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378 /* Else there's nothing to do.
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379 * If gc_refs > 0, it must be in move_unreachable's 'young'
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380 * list, and move_unreachable will eventually get to it.
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381 * If gc_refs == GC_REACHABLE, it's either in some other
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382 * generation so we don't care about it, or move_unreachable
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383 * already dealt with it.
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384 * If gc_refs == GC_UNTRACKED, it must be ignored.
|
|
|
385 */
|
|
|
386 else {
|
|
|
387 assert(gc_refs > 0
|
|
|
388 || gc_refs == GC_REACHABLE
|
|
|
389 || gc_refs == GC_UNTRACKED);
|
|
|
390 }
|
|
|
391 }
|
|
|
392 return 0;
|
|
|
393 }
|
|
|
394
|
|
|
395 /* Move the unreachable objects from young to unreachable. After this,
|
|
|
396 * all objects in young have gc_refs = GC_REACHABLE, and all objects in
|
|
|
397 * unreachable have gc_refs = GC_TENTATIVELY_UNREACHABLE. All tracked
|
|
|
398 * gc objects not in young or unreachable still have gc_refs = GC_REACHABLE.
|
|
|
399 * All objects in young after this are directly or indirectly reachable
|
|
|
400 * from outside the original young; and all objects in unreachable are
|
|
|
401 * not.
|
|
|
402 */
|
|
|
403 static void
|
|
|
404 move_unreachable(PyGC_Head *young, PyGC_Head *unreachable)
|
|
|
405 {
|
|
|
406 PyGC_Head *gc = young->gc.gc_next;
|
|
|
407
|
|
|
408 /* Invariants: all objects "to the left" of us in young have gc_refs
|
|
|
409 * = GC_REACHABLE, and are indeed reachable (directly or indirectly)
|
|
|
410 * from outside the young list as it was at entry. All other objects
|
|
|
411 * from the original young "to the left" of us are in unreachable now,
|
|
|
412 * and have gc_refs = GC_TENTATIVELY_UNREACHABLE. All objects to the
|
|
|
413 * left of us in 'young' now have been scanned, and no objects here
|
|
|
414 * or to the right have been scanned yet.
|
|
|
415 */
|
|
|
416
|
|
|
417 while (gc != young) {
|
|
|
418 PyGC_Head *next;
|
|
|
419
|
|
|
420 if (gc->gc.gc_refs) {
|
|
|
421 /* gc is definitely reachable from outside the
|
|
|
422 * original 'young'. Mark it as such, and traverse
|
|
|
423 * its pointers to find any other objects that may
|
|
|
424 * be directly reachable from it. Note that the
|
|
|
425 * call to tp_traverse may append objects to young,
|
|
|
426 * so we have to wait until it returns to determine
|
|
|
427 * the next object to visit.
|
|
|
428 */
|
|
|
429 PyObject *op = FROM_GC(gc);
|
|
|
430 traverseproc traverse = Py_TYPE(op)->tp_traverse;
|
|
|
431 assert(gc->gc.gc_refs > 0);
|
|
|
432 gc->gc.gc_refs = GC_REACHABLE;
|
|
|
433 (void) traverse(op,
|
|
|
434 (visitproc)visit_reachable,
|
|
|
435 (void *)young);
|
|
|
436 next = gc->gc.gc_next;
|
|
|
437 if (PyTuple_CheckExact(op)) {
|
|
|
438 _PyTuple_MaybeUntrack(op);
|
|
|
439 }
|
|
|
440 else if (PyDict_CheckExact(op)) {
|
|
|
441 _PyDict_MaybeUntrack(op);
|
|
|
442 }
|
|
|
443 }
|
|
|
444 else {
|
|
|
445 /* This *may* be unreachable. To make progress,
|
|
|
446 * assume it is. gc isn't directly reachable from
|
|
|
447 * any object we've already traversed, but may be
|
|
|
448 * reachable from an object we haven't gotten to yet.
|
|
|
449 * visit_reachable will eventually move gc back into
|
|
|
450 * young if that's so, and we'll see it again.
|
|
|
451 */
|
|
|
452 next = gc->gc.gc_next;
|
|
|
453 gc_list_move(gc, unreachable);
|
|
|
454 gc->gc.gc_refs = GC_TENTATIVELY_UNREACHABLE;
|
|
|
455 }
|
|
|
456 gc = next;
|
|
|
457 }
|
|
|
458 }
|
|
|
459
|
|
|
460 /* Return true if object has a finalization method. */
|
|
|
461 static int
|
|
|
462 has_finalizer(PyObject *op)
|
|
|
463 {
|
|
|
464 if (PyGen_CheckExact(op))
|
|
|
465 return PyGen_NeedsFinalizing((PyGenObject *)op);
|
|
|
466 else
|
|
|
467 return op->ob_type->tp_del != NULL;
|
|
|
468 }
|
|
|
469
|
|
|
470 /* Move the objects in unreachable with __del__ methods into `finalizers`.
|
|
|
471 * Objects moved into `finalizers` have gc_refs set to GC_REACHABLE; the
|
|
|
472 * objects remaining in unreachable are left at GC_TENTATIVELY_UNREACHABLE.
|
|
|
473 */
|
|
|
474 static void
|
|
|
475 move_finalizers(PyGC_Head *unreachable, PyGC_Head *finalizers)
|
|
|
476 {
|
|
|
477 PyGC_Head *gc;
|
|
|
478 PyGC_Head *next;
|
|
|
479
|
|
|
480 /* March over unreachable. Move objects with finalizers into
|
|
|
481 * `finalizers`.
|
|
|
482 */
|
|
|
483 for (gc = unreachable->gc.gc_next; gc != unreachable; gc = next) {
|
|
|
484 PyObject *op = FROM_GC(gc);
|
|
|
485
|
|
|
486 assert(IS_TENTATIVELY_UNREACHABLE(op));
|
|
|
487 next = gc->gc.gc_next;
|
|
|
488
|
|
|
489 if (has_finalizer(op)) {
|
|
|
490 gc_list_move(gc, finalizers);
|
|
|
491 gc->gc.gc_refs = GC_REACHABLE;
|
|
|
492 }
|
|
|
493 }
|
|
|
494 }
|
|
|
495
|
|
|
496 /* A traversal callback for move_finalizer_reachable. */
|
|
|
497 static int
|
|
|
498 visit_move(PyObject *op, PyGC_Head *tolist)
|
|
|
499 {
|
|
|
500 if (PyObject_IS_GC(op)) {
|
|
|
501 if (IS_TENTATIVELY_UNREACHABLE(op)) {
|
|
|
502 PyGC_Head *gc = AS_GC(op);
|
|
|
503 gc_list_move(gc, tolist);
|
|
|
504 gc->gc.gc_refs = GC_REACHABLE;
|
|
|
505 }
|
|
|
506 }
|
|
|
507 return 0;
|
|
|
508 }
|
|
|
509
|
|
|
510 /* Move objects that are reachable from finalizers, from the unreachable set
|
|
|
511 * into finalizers set.
|
|
|
512 */
|
|
|
513 static void
|
|
|
514 move_finalizer_reachable(PyGC_Head *finalizers)
|
|
|
515 {
|
|
|
516 traverseproc traverse;
|
|
|
517 PyGC_Head *gc = finalizers->gc.gc_next;
|
|
|
518 for (; gc != finalizers; gc = gc->gc.gc_next) {
|
|
|
519 /* Note that the finalizers list may grow during this. */
|
|
|
520 traverse = Py_TYPE(FROM_GC(gc))->tp_traverse;
|
|
|
521 (void) traverse(FROM_GC(gc),
|
|
|
522 (visitproc)visit_move,
|
|
|
523 (void *)finalizers);
|
|
|
524 }
|
|
|
525 }
|
|
|
526
|
|
|
527 /* Clear all weakrefs to unreachable objects, and if such a weakref has a
|
|
|
528 * callback, invoke it if necessary. Note that it's possible for such
|
|
|
529 * weakrefs to be outside the unreachable set -- indeed, those are precisely
|
|
|
530 * the weakrefs whose callbacks must be invoked. See gc_weakref.txt for
|
|
|
531 * overview & some details. Some weakrefs with callbacks may be reclaimed
|
|
|
532 * directly by this routine; the number reclaimed is the return value. Other
|
|
|
533 * weakrefs with callbacks may be moved into the `old` generation. Objects
|
|
|
534 * moved into `old` have gc_refs set to GC_REACHABLE; the objects remaining in
|
|
|
535 * unreachable are left at GC_TENTATIVELY_UNREACHABLE. When this returns,
|
|
|
536 * no object in `unreachable` is weakly referenced anymore.
|
|
|
537 */
|
|
|
538 static int
|
|
|
539 handle_weakrefs(PyGC_Head *unreachable, PyGC_Head *old)
|
|
|
540 {
|
|
|
541 PyGC_Head *gc;
|
|
|
542 PyObject *op; /* generally FROM_GC(gc) */
|
|
|
543 PyWeakReference *wr; /* generally a cast of op */
|
|
|
544 PyGC_Head wrcb_to_call; /* weakrefs with callbacks to call */
|
|
|
545 PyGC_Head *next;
|
|
|
546 int num_freed = 0;
|
|
|
547
|
|
|
548 gc_list_init(&wrcb_to_call);
|
|
|
549
|
|
|
550 /* Clear all weakrefs to the objects in unreachable. If such a weakref
|
|
|
551 * also has a callback, move it into `wrcb_to_call` if the callback
|
|
|
552 * needs to be invoked. Note that we cannot invoke any callbacks until
|
|
|
553 * all weakrefs to unreachable objects are cleared, lest the callback
|
|
|
554 * resurrect an unreachable object via a still-active weakref. We
|
|
|
555 * make another pass over wrcb_to_call, invoking callbacks, after this
|
|
|
556 * pass completes.
|
|
|
557 */
|
|
|
558 for (gc = unreachable->gc.gc_next; gc != unreachable; gc = next) {
|
|
|
559 PyWeakReference **wrlist;
|
|
|
560
|
|
|
561 op = FROM_GC(gc);
|
|
|
562 assert(IS_TENTATIVELY_UNREACHABLE(op));
|
|
|
563 next = gc->gc.gc_next;
|
|
|
564
|
|
|
565 if (! PyType_SUPPORTS_WEAKREFS(Py_TYPE(op)))
|
|
|
566 continue;
|
|
|
567
|
|
|
568 /* It supports weakrefs. Does it have any? */
|
|
|
569 wrlist = (PyWeakReference **)
|
|
|
570 PyObject_GET_WEAKREFS_LISTPTR(op);
|
|
|
571
|
|
|
572 /* `op` may have some weakrefs. March over the list, clear
|
|
|
573 * all the weakrefs, and move the weakrefs with callbacks
|
|
|
574 * that must be called into wrcb_to_call.
|
|
|
575 */
|
|
|
576 for (wr = *wrlist; wr != NULL; wr = *wrlist) {
|
|
|
577 PyGC_Head *wrasgc; /* AS_GC(wr) */
|
|
|
578
|
|
|
579 /* _PyWeakref_ClearRef clears the weakref but leaves
|
|
|
580 * the callback pointer intact. Obscure: it also
|
|
|
581 * changes *wrlist.
|
|
|
582 */
|
|
|
583 assert(wr->wr_object == op);
|
|
|
584 _PyWeakref_ClearRef(wr);
|
|
|
585 assert(wr->wr_object == Py_None);
|
|
|
586 if (wr->wr_callback == NULL)
|
|
|
587 continue; /* no callback */
|
|
|
588
|
|
|
589 /* Headache time. `op` is going away, and is weakly referenced by
|
|
|
590 * `wr`, which has a callback. Should the callback be invoked? If wr
|
|
|
591 * is also trash, no:
|
|
|
592 *
|
|
|
593 * 1. There's no need to call it. The object and the weakref are
|
|
|
594 * both going away, so it's legitimate to pretend the weakref is
|
|
|
595 * going away first. The user has to ensure a weakref outlives its
|
|
|
596 * referent if they want a guarantee that the wr callback will get
|
|
|
597 * invoked.
|
|
|
598 *
|
|
|
599 * 2. It may be catastrophic to call it. If the callback is also in
|
|
|
600 * cyclic trash (CT), then although the CT is unreachable from
|
|
|
601 * outside the current generation, CT may be reachable from the
|
|
|
602 * callback. Then the callback could resurrect insane objects.
|
|
|
603 *
|
|
|
604 * Since the callback is never needed and may be unsafe in this case,
|
|
|
605 * wr is simply left in the unreachable set. Note that because we
|
|
|
606 * already called _PyWeakref_ClearRef(wr), its callback will never
|
|
|
607 * trigger.
|
|
|
608 *
|
|
|
609 * OTOH, if wr isn't part of CT, we should invoke the callback: the
|
|
|
610 * weakref outlived the trash. Note that since wr isn't CT in this
|
|
|
611 * case, its callback can't be CT either -- wr acted as an external
|
|
|
612 * root to this generation, and therefore its callback did too. So
|
|
|
613 * nothing in CT is reachable from the callback either, so it's hard
|
|
|
614 * to imagine how calling it later could create a problem for us. wr
|
|
|
615 * is moved to wrcb_to_call in this case.
|
|
|
616 */
|
|
|
617 if (IS_TENTATIVELY_UNREACHABLE(wr))
|
|
|
618 continue;
|
|
|
619 assert(IS_REACHABLE(wr));
|
|
|
620
|
|
|
621 /* Create a new reference so that wr can't go away
|
|
|
622 * before we can process it again.
|
|
|
623 */
|
|
|
624 Py_INCREF(wr);
|
|
|
625
|
|
|
626 /* Move wr to wrcb_to_call, for the next pass. */
|
|
|
627 wrasgc = AS_GC(wr);
|
|
|
628 assert(wrasgc != next); /* wrasgc is reachable, but
|
|
|
629 next isn't, so they can't
|
|
|
630 be the same */
|
|
|
631 gc_list_move(wrasgc, &wrcb_to_call);
|
|
|
632 }
|
|
|
633 }
|
|
|
634
|
|
|
635 /* Invoke the callbacks we decided to honor. It's safe to invoke them
|
|
|
636 * because they can't reference unreachable objects.
|
|
|
637 */
|
|
|
638 while (! gc_list_is_empty(&wrcb_to_call)) {
|
|
|
639 PyObject *temp;
|
|
|
640 PyObject *callback;
|
|
|
641
|
|
|
642 gc = wrcb_to_call.gc.gc_next;
|
|
|
643 op = FROM_GC(gc);
|
|
|
644 assert(IS_REACHABLE(op));
|
|
|
645 assert(PyWeakref_Check(op));
|
|
|
646 wr = (PyWeakReference *)op;
|
|
|
647 callback = wr->wr_callback;
|
|
|
648 assert(callback != NULL);
|
|
|
649
|
|
|
650 /* copy-paste of weakrefobject.c's handle_callback() */
|
|
|
651 temp = PyObject_CallFunctionObjArgs(callback, wr, NULL);
|
|
|
652 if (temp == NULL)
|
|
|
653 PyErr_WriteUnraisable(callback);
|
|
|
654 else
|
|
|
655 Py_DECREF(temp);
|
|
|
656
|
|
|
657 /* Give up the reference we created in the first pass. When
|
|
|
658 * op's refcount hits 0 (which it may or may not do right now),
|
|
|
659 * op's tp_dealloc will decref op->wr_callback too. Note
|
|
|
660 * that the refcount probably will hit 0 now, and because this
|
|
|
661 * weakref was reachable to begin with, gc didn't already
|
|
|
662 * add it to its count of freed objects. Example: a reachable
|
|
|
663 * weak value dict maps some key to this reachable weakref.
|
|
|
664 * The callback removes this key->weakref mapping from the
|
|
|
665 * dict, leaving no other references to the weakref (excepting
|
|
|
666 * ours).
|
|
|
667 */
|
|
|
668 Py_DECREF(op);
|
|
|
669 if (wrcb_to_call.gc.gc_next == gc) {
|
|
|
670 /* object is still alive -- move it */
|
|
|
671 gc_list_move(gc, old);
|
|
|
672 }
|
|
|
673 else
|
|
|
674 ++num_freed;
|
|
|
675 }
|
|
|
676
|
|
|
677 return num_freed;
|
|
|
678 }
|
|
|
679
|
|
|
680 static void
|
|
|
681 debug_cycle(char *msg, PyObject *op)
|
|
|
682 {
|
|
|
683 PySys_WriteStderr("gc: %.100s <%.100s %p>\n",
|
|
|
684 msg, Py_TYPE(op)->tp_name, op);
|
|
|
685 }
|
|
|
686
|
|
|
687 /* Handle uncollectable garbage (cycles with finalizers, and stuff reachable
|
|
|
688 * only from such cycles).
|
|
|
689 * If DEBUG_SAVEALL, all objects in finalizers are appended to the module
|
|
|
690 * garbage list (a Python list), else only the objects in finalizers with
|
|
|
691 * __del__ methods are appended to garbage. All objects in finalizers are
|
|
|
692 * merged into the old list regardless.
|
|
|
693 * Returns 0 if all OK, <0 on error (out of memory to grow the garbage list).
|
|
|
694 * The finalizers list is made empty on a successful return.
|
|
|
695 */
|
|
|
696 static int
|
|
|
697 handle_finalizers(PyGC_Head *finalizers, PyGC_Head *old)
|
|
|
698 {
|
|
|
699 PyGC_Head *gc = finalizers->gc.gc_next;
|
|
|
700
|
|
|
701 if (garbage == NULL) {
|
|
|
702 garbage = PyList_New(0);
|
|
|
703 if (garbage == NULL)
|
|
|
704 Py_FatalError("gc couldn't create gc.garbage list");
|
|
|
705 }
|
|
|
706 for (; gc != finalizers; gc = gc->gc.gc_next) {
|
|
|
707 PyObject *op = FROM_GC(gc);
|
|
|
708
|
|
|
709 if ((debug & DEBUG_SAVEALL) || has_finalizer(op)) {
|
|
|
710 if (PyList_Append(garbage, op) < 0)
|
|
|
711 return -1;
|
|
|
712 }
|
|
|
713 }
|
|
|
714
|
|
|
715 gc_list_merge(finalizers, old);
|
|
|
716 return 0;
|
|
|
717 }
|
|
|
718
|
|
|
719 /* Break reference cycles by clearing the containers involved. This is
|
|
|
720 * tricky business as the lists can be changing and we don't know which
|
|
|
721 * objects may be freed. It is possible I screwed something up here.
|
|
|
722 */
|
|
|
723 static void
|
|
|
724 delete_garbage(PyGC_Head *collectable, PyGC_Head *old)
|
|
|
725 {
|
|
|
726 inquiry clear;
|
|
|
727
|
|
|
728 while (!gc_list_is_empty(collectable)) {
|
|
|
729 PyGC_Head *gc = collectable->gc.gc_next;
|
|
|
730 PyObject *op = FROM_GC(gc);
|
|
|
731
|
|
|
732 assert(IS_TENTATIVELY_UNREACHABLE(op));
|
|
|
733 if (debug & DEBUG_SAVEALL) {
|
|
|
734 PyList_Append(garbage, op);
|
|
|
735 }
|
|
|
736 else {
|
|
|
737 if ((clear = Py_TYPE(op)->tp_clear) != NULL) {
|
|
|
738 Py_INCREF(op);
|
|
|
739 clear(op);
|
|
|
740 Py_DECREF(op);
|
|
|
741 }
|
|
|
742 }
|
|
|
743 if (collectable->gc.gc_next == gc) {
|
|
|
744 /* object is still alive, move it, it may die later */
|
|
|
745 gc_list_move(gc, old);
|
|
|
746 gc->gc.gc_refs = GC_REACHABLE;
|
|
|
747 }
|
|
|
748 }
|
|
|
749 }
|
|
|
750
|
|
|
751 /* Clear all free lists
|
|
|
752 * All free lists are cleared during the collection of the highest generation.
|
|
|
753 * Allocated items in the free list may keep a pymalloc arena occupied.
|
|
|
754 * Clearing the free lists may give back memory to the OS earlier.
|
|
|
755 */
|
|
|
756 static void
|
|
|
757 clear_freelists(void)
|
|
|
758 {
|
|
|
759 (void)PyMethod_ClearFreeList();
|
|
|
760 (void)PyFrame_ClearFreeList();
|
|
|
761 (void)PyCFunction_ClearFreeList();
|
|
|
762 (void)PyTuple_ClearFreeList();
|
|
|
763 (void)PyUnicode_ClearFreeList();
|
|
|
764 (void)PyFloat_ClearFreeList();
|
|
|
765 }
|
|
|
766
|
|
|
767 static double
|
|
|
768 get_time(void)
|
|
|
769 {
|
|
|
770 double result = 0;
|
|
|
771 if (tmod != NULL) {
|
|
|
772 PyObject *f = PyObject_CallMethod(tmod, "time", NULL);
|
|
|
773 if (f == NULL) {
|
|
|
774 PyErr_Clear();
|
|
|
775 }
|
|
|
776 else {
|
|
|
777 if (PyFloat_Check(f))
|
|
|
778 result = PyFloat_AsDouble(f);
|
|
|
779 Py_DECREF(f);
|
|
|
780 }
|
|
|
781 }
|
|
|
782 return result;
|
|
|
783 }
|
|
|
784
|
|
|
785 /* This is the main function. Read this to understand how the
|
|
|
786 * collection process works. */
|
|
|
787 static Py_ssize_t
|
|
|
788 collect(int generation)
|
|
|
789 {
|
|
|
790 int i;
|
|
|
791 Py_ssize_t m = 0; /* # objects collected */
|
|
|
792 Py_ssize_t n = 0; /* # unreachable objects that couldn't be collected */
|
|
|
793 PyGC_Head *young; /* the generation we are examining */
|
|
|
794 PyGC_Head *old; /* next older generation */
|
|
|
795 PyGC_Head unreachable; /* non-problematic unreachable trash */
|
|
|
796 PyGC_Head finalizers; /* objects with, & reachable from, __del__ */
|
|
|
797 PyGC_Head *gc;
|
|
|
798 double t1 = 0.0;
|
|
|
799
|
|
|
800 if (delstr == NULL) {
|
|
|
801 delstr = PyUnicode_InternFromString("__del__");
|
|
|
802 if (delstr == NULL)
|
|
|
803 Py_FatalError("gc couldn't allocate \"__del__\"");
|
|
|
804 }
|
|
|
805
|
|
|
806 if (debug & DEBUG_STATS) {
|
|
|
807 PySys_WriteStderr("gc: collecting generation %d...\n",
|
|
|
808 generation);
|
|
|
809 PySys_WriteStderr("gc: objects in each generation:");
|
|
|
810 for (i = 0; i < NUM_GENERATIONS; i++)
|
|
|
811 PySys_WriteStderr(" %" PY_FORMAT_SIZE_T "d",
|
|
|
812 gc_list_size(GEN_HEAD(i)));
|
|
|
813 t1 = get_time();
|
|
|
814 PySys_WriteStderr("\n");
|
|
|
815 }
|
|
|
816
|
|
|
817 /* update collection and allocation counters */
|
|
|
818 if (generation+1 < NUM_GENERATIONS)
|
|
|
819 generations[generation+1].count += 1;
|
|
|
820 for (i = 0; i <= generation; i++)
|
|
|
821 generations[i].count = 0;
|
|
|
822
|
|
|
823 /* merge younger generations with one we are currently collecting */
|
|
|
824 for (i = 0; i < generation; i++) {
|
|
|
825 gc_list_merge(GEN_HEAD(i), GEN_HEAD(generation));
|
|
|
826 }
|
|
|
827
|
|
|
828 /* handy references */
|
|
|
829 young = GEN_HEAD(generation);
|
|
|
830 if (generation < NUM_GENERATIONS-1)
|
|
|
831 old = GEN_HEAD(generation+1);
|
|
|
832 else
|
|
|
833 old = young;
|
|
|
834
|
|
|
835 /* Using ob_refcnt and gc_refs, calculate which objects in the
|
|
|
836 * container set are reachable from outside the set (i.e., have a
|
|
|
837 * refcount greater than 0 when all the references within the
|
|
|
838 * set are taken into account).
|
|
|
839 */
|
|
|
840 update_refs(young);
|
|
|
841 subtract_refs(young);
|
|
|
842
|
|
|
843 /* Leave everything reachable from outside young in young, and move
|
|
|
844 * everything else (in young) to unreachable.
|
|
|
845 * NOTE: This used to move the reachable objects into a reachable
|
|
|
846 * set instead. But most things usually turn out to be reachable,
|
|
|
847 * so it's more efficient to move the unreachable things.
|
|
|
848 */
|
|
|
849 gc_list_init(&unreachable);
|
|
|
850 move_unreachable(young, &unreachable);
|
|
|
851
|
|
|
852 /* Move reachable objects to next generation. */
|
|
|
853 if (young != old) {
|
|
|
854 if (generation == NUM_GENERATIONS - 2) {
|
|
|
855 long_lived_pending += gc_list_size(young);
|
|
|
856 }
|
|
|
857 gc_list_merge(young, old);
|
|
|
858 }
|
|
|
859 else {
|
|
|
860 long_lived_pending = 0;
|
|
|
861 long_lived_total = gc_list_size(young);
|
|
|
862 }
|
|
|
863
|
|
|
864 /* All objects in unreachable are trash, but objects reachable from
|
|
|
865 * finalizers can't safely be deleted. Python programmers should take
|
|
|
866 * care not to create such things. For Python, finalizers means
|
|
|
867 * instance objects with __del__ methods. Weakrefs with callbacks
|
|
|
868 * can also call arbitrary Python code but they will be dealt with by
|
|
|
869 * handle_weakrefs().
|
|
|
870 */
|
|
|
871 gc_list_init(&finalizers);
|
|
|
872 move_finalizers(&unreachable, &finalizers);
|
|
|
873 /* finalizers contains the unreachable objects with a finalizer;
|
|
|
874 * unreachable objects reachable *from* those are also uncollectable,
|
|
|
875 * and we move those into the finalizers list too.
|
|
|
876 */
|
|
|
877 move_finalizer_reachable(&finalizers);
|
|
|
878
|
|
|
879 /* Collect statistics on collectable objects found and print
|
|
|
880 * debugging information.
|
|
|
881 */
|
|
|
882 for (gc = unreachable.gc.gc_next; gc != &unreachable;
|
|
|
883 gc = gc->gc.gc_next) {
|
|
|
884 m++;
|
|
|
885 if (debug & DEBUG_COLLECTABLE) {
|
|
|
886 debug_cycle("collectable", FROM_GC(gc));
|
|
|
887 }
|
|
|
888 }
|
|
|
889
|
|
|
890 /* Clear weakrefs and invoke callbacks as necessary. */
|
|
|
891 m += handle_weakrefs(&unreachable, old);
|
|
|
892
|
|
|
893 /* Call tp_clear on objects in the unreachable set. This will cause
|
|
|
894 * the reference cycles to be broken. It may also cause some objects
|
|
|
895 * in finalizers to be freed.
|
|
|
896 */
|
|
|
897 delete_garbage(&unreachable, old);
|
|
|
898
|
|
|
899 /* Collect statistics on uncollectable objects found and print
|
|
|
900 * debugging information. */
|
|
|
901 for (gc = finalizers.gc.gc_next;
|
|
|
902 gc != &finalizers;
|
|
|
903 gc = gc->gc.gc_next) {
|
|
|
904 n++;
|
|
|
905 if (debug & DEBUG_UNCOLLECTABLE)
|
|
|
906 debug_cycle("uncollectable", FROM_GC(gc));
|
|
|
907 }
|
|
|
908 if (debug & DEBUG_STATS) {
|
|
|
909 double t2 = get_time();
|
|
|
910 if (m == 0 && n == 0)
|
|
|
911 PySys_WriteStderr("gc: done");
|
|
|
912 else
|
|
|
913 PySys_WriteStderr(
|
|
|
914 "gc: done, "
|
|
|
915 "%" PY_FORMAT_SIZE_T "d unreachable, "
|
|
|
916 "%" PY_FORMAT_SIZE_T "d uncollectable",
|
|
|
917 n+m, n);
|
|
|
918 if (t1 && t2) {
|
|
|
919 PySys_WriteStderr(", %.4fs elapsed", t2-t1);
|
|
|
920 }
|
|
|
921 PySys_WriteStderr(".\n");
|
|
|
922 }
|
|
|
923
|
|
|
924 /* Append instances in the uncollectable set to a Python
|
|
|
925 * reachable list of garbage. The programmer has to deal with
|
|
|
926 * this if they insist on creating this type of structure.
|
|
|
927 */
|
|
|
928 (void)handle_finalizers(&finalizers, old);
|
|
|
929
|
|
|
930 /* Clear free list only during the collection of the highest
|
|
|
931 * generation */
|
|
|
932 if (generation == NUM_GENERATIONS-1) {
|
|
|
933 clear_freelists();
|
|
|
934 }
|
|
|
935
|
|
|
936 if (PyErr_Occurred()) {
|
|
|
937 if (gc_str == NULL)
|
|
|
938 gc_str = PyUnicode_FromString("garbage collection");
|
|
|
939 PyErr_WriteUnraisable(gc_str);
|
|
|
940 Py_FatalError("unexpected exception during garbage collection");
|
|
|
941 }
|
|
|
942 return n+m;
|
|
|
943 }
|
|
|
944
|
|
|
945 static Py_ssize_t
|
|
|
946 collect_generations(void)
|
|
|
947 {
|
|
|
948 int i;
|
|
|
949 Py_ssize_t n = 0;
|
|
|
950
|
|
|
951 /* Find the oldest generation (highest numbered) where the count
|
|
|
952 * exceeds the threshold. Objects in the that generation and
|
|
|
953 * generations younger than it will be collected. */
|
|
|
954 for (i = NUM_GENERATIONS-1; i >= 0; i--) {
|
|
|
955 if (generations[i].count > generations[i].threshold) {
|
|
|
956 /* Avoid quadratic performance degradation in number
|
|
|
957 of tracked objects. See comments at the beginning
|
|
|
958 of this file, and issue #4074.
|
|
|
959 */
|
|
|
960 if (i == NUM_GENERATIONS - 1
|
|
|
961 && long_lived_pending < long_lived_total / 4)
|
|
|
962 continue;
|
|
|
963 n = collect(i);
|
|
|
964 break;
|
|
|
965 }
|
|
|
966 }
|
|
|
967 return n;
|
|
|
968 }
|
|
|
969
|
|
|
970 PyDoc_STRVAR(gc_enable__doc__,
|
|
|
971 "enable() -> None\n"
|
|
|
972 "\n"
|
|
|
973 "Enable automatic garbage collection.\n");
|
|
|
974
|
|
|
975 static PyObject *
|
|
|
976 gc_enable(PyObject *self, PyObject *noargs)
|
|
|
977 {
|
|
|
978 enabled = 1;
|
|
|
979 Py_INCREF(Py_None);
|
|
|
980 return Py_None;
|
|
|
981 }
|
|
|
982
|
|
|
983 PyDoc_STRVAR(gc_disable__doc__,
|
|
|
984 "disable() -> None\n"
|
|
|
985 "\n"
|
|
|
986 "Disable automatic garbage collection.\n");
|
|
|
987
|
|
|
988 static PyObject *
|
|
|
989 gc_disable(PyObject *self, PyObject *noargs)
|
|
|
990 {
|
|
|
991 enabled = 0;
|
|
|
992 Py_INCREF(Py_None);
|
|
|
993 return Py_None;
|
|
|
994 }
|
|
|
995
|
|
|
996 PyDoc_STRVAR(gc_isenabled__doc__,
|
|
|
997 "isenabled() -> status\n"
|
|
|
998 "\n"
|
|
|
999 "Returns true if automatic garbage collection is enabled.\n");
|
|
|
1000
|
|
|
1001 static PyObject *
|
|
|
1002 gc_isenabled(PyObject *self, PyObject *noargs)
|
|
|
1003 {
|
|
|
1004 return PyBool_FromLong((long)enabled);
|
|
|
1005 }
|
|
|
1006
|
|
|
1007 PyDoc_STRVAR(gc_collect__doc__,
|
|
|
1008 "collect([generation]) -> n\n"
|
|
|
1009 "\n"
|
|
|
1010 "With no arguments, run a full collection. The optional argument\n"
|
|
|
1011 "may be an integer specifying which generation to collect. A ValueError\n"
|
|
|
1012 "is raised if the generation number is invalid.\n\n"
|
|
|
1013 "The number of unreachable objects is returned.\n");
|
|
|
1014
|
|
|
1015 static PyObject *
|
|
|
1016 gc_collect(PyObject *self, PyObject *args, PyObject *kws)
|
|
|
1017 {
|
|
|
1018 static char *keywords[] = {"generation", NULL};
|
|
|
1019 int genarg = NUM_GENERATIONS - 1;
|
|
|
1020 Py_ssize_t n;
|
|
|
1021
|
|
|
1022 if (!PyArg_ParseTupleAndKeywords(args, kws, "|i", keywords, &genarg))
|
|
|
1023 return NULL;
|
|
|
1024
|
|
|
1025 else if (genarg < 0 || genarg >= NUM_GENERATIONS) {
|
|
|
1026 PyErr_SetString(PyExc_ValueError, "invalid generation");
|
|
|
1027 return NULL;
|
|
|
1028 }
|
|
|
1029
|
|
|
1030 if (collecting)
|
|
|
1031 n = 0; /* already collecting, don't do anything */
|
|
|
1032 else {
|
|
|
1033 collecting = 1;
|
|
|
1034 n = collect(genarg);
|
|
|
1035 collecting = 0;
|
|
|
1036 }
|
|
|
1037
|
|
|
1038 return PyLong_FromSsize_t(n);
|
|
|
1039 }
|
|
|
1040
|
|
|
1041 PyDoc_STRVAR(gc_set_debug__doc__,
|
|
|
1042 "set_debug(flags) -> None\n"
|
|
|
1043 "\n"
|
|
|
1044 "Set the garbage collection debugging flags. Debugging information is\n"
|
|
|
1045 "written to sys.stderr.\n"
|
|
|
1046 "\n"
|
|
|
1047 "flags is an integer and can have the following bits turned on:\n"
|
|
|
1048 "\n"
|
|
|
1049 " DEBUG_STATS - Print statistics during collection.\n"
|
|
|
1050 " DEBUG_COLLECTABLE - Print collectable objects found.\n"
|
|
|
1051 " DEBUG_UNCOLLECTABLE - Print unreachable but uncollectable objects found.\n"
|
|
|
1052 " DEBUG_SAVEALL - Save objects to gc.garbage rather than freeing them.\n"
|
|
|
1053 " DEBUG_LEAK - Debug leaking programs (everything but STATS).\n");
|
|
|
1054
|
|
|
1055 static PyObject *
|
|
|
1056 gc_set_debug(PyObject *self, PyObject *args)
|
|
|
1057 {
|
|
|
1058 if (!PyArg_ParseTuple(args, "i:set_debug", &debug))
|
|
|
1059 return NULL;
|
|
|
1060
|
|
|
1061 Py_INCREF(Py_None);
|
|
|
1062 return Py_None;
|
|
|
1063 }
|
|
|
1064
|
|
|
1065 PyDoc_STRVAR(gc_get_debug__doc__,
|
|
|
1066 "get_debug() -> flags\n"
|
|
|
1067 "\n"
|
|
|
1068 "Get the garbage collection debugging flags.\n");
|
|
|
1069
|
|
|
1070 static PyObject *
|
|
|
1071 gc_get_debug(PyObject *self, PyObject *noargs)
|
|
|
1072 {
|
|
|
1073 return Py_BuildValue("i", debug);
|
|
|
1074 }
|
|
|
1075
|
|
|
1076 PyDoc_STRVAR(gc_set_thresh__doc__,
|
|
|
1077 "set_threshold(threshold0, [threshold1, threshold2]) -> None\n"
|
|
|
1078 "\n"
|
|
|
1079 "Sets the collection thresholds. Setting threshold0 to zero disables\n"
|
|
|
1080 "collection.\n");
|
|
|
1081
|
|
|
1082 static PyObject *
|
|
|
1083 gc_set_thresh(PyObject *self, PyObject *args)
|
|
|
1084 {
|
|
|
1085 int i;
|
|
|
1086 if (!PyArg_ParseTuple(args, "i|ii:set_threshold",
|
|
|
1087 &generations[0].threshold,
|
|
|
1088 &generations[1].threshold,
|
|
|
1089 &generations[2].threshold))
|
|
|
1090 return NULL;
|
|
|
1091 for (i = 2; i < NUM_GENERATIONS; i++) {
|
|
|
1092 /* generations higher than 2 get the same threshold */
|
|
|
1093 generations[i].threshold = generations[2].threshold;
|
|
|
1094 }
|
|
|
1095
|
|
|
1096 Py_INCREF(Py_None);
|
|
|
1097 return Py_None;
|
|
|
1098 }
|
|
|
1099
|
|
|
1100 PyDoc_STRVAR(gc_get_thresh__doc__,
|
|
|
1101 "get_threshold() -> (threshold0, threshold1, threshold2)\n"
|
|
|
1102 "\n"
|
|
|
1103 "Return the current collection thresholds\n");
|
|
|
1104
|
|
|
1105 static PyObject *
|
|
|
1106 gc_get_thresh(PyObject *self, PyObject *noargs)
|
|
|
1107 {
|
|
|
1108 return Py_BuildValue("(iii)",
|
|
|
1109 generations[0].threshold,
|
|
|
1110 generations[1].threshold,
|
|
|
1111 generations[2].threshold);
|
|
|
1112 }
|
|
|
1113
|
|
|
1114 PyDoc_STRVAR(gc_get_count__doc__,
|
|
|
1115 "get_count() -> (count0, count1, count2)\n"
|
|
|
1116 "\n"
|
|
|
1117 "Return the current collection counts\n");
|
|
|
1118
|
|
|
1119 static PyObject *
|
|
|
1120 gc_get_count(PyObject *self, PyObject *noargs)
|
|
|
1121 {
|
|
|
1122 return Py_BuildValue("(iii)",
|
|
|
1123 generations[0].count,
|
|
|
1124 generations[1].count,
|
|
|
1125 generations[2].count);
|
|
|
1126 }
|
|
|
1127
|
|
|
1128 static int
|
|
|
1129 referrersvisit(PyObject* obj, PyObject *objs)
|
|
|
1130 {
|
|
|
1131 Py_ssize_t i;
|
|
|
1132 for (i = 0; i < PyTuple_GET_SIZE(objs); i++)
|
|
|
1133 if (PyTuple_GET_ITEM(objs, i) == obj)
|
|
|
1134 return 1;
|
|
|
1135 return 0;
|
|
|
1136 }
|
|
|
1137
|
|
|
1138 static int
|
|
|
1139 gc_referrers_for(PyObject *objs, PyGC_Head *list, PyObject *resultlist)
|
|
|
1140 {
|
|
|
1141 PyGC_Head *gc;
|
|
|
1142 PyObject *obj;
|
|
|
1143 traverseproc traverse;
|
|
|
1144 for (gc = list->gc.gc_next; gc != list; gc = gc->gc.gc_next) {
|
|
|
1145 obj = FROM_GC(gc);
|
|
|
1146 traverse = Py_TYPE(obj)->tp_traverse;
|
|
|
1147 if (obj == objs || obj == resultlist)
|
|
|
1148 continue;
|
|
|
1149 if (traverse(obj, (visitproc)referrersvisit, objs)) {
|
|
|
1150 if (PyList_Append(resultlist, obj) < 0)
|
|
|
1151 return 0; /* error */
|
|
|
1152 }
|
|
|
1153 }
|
|
|
1154 return 1; /* no error */
|
|
|
1155 }
|
|
|
1156
|
|
|
1157 PyDoc_STRVAR(gc_get_referrers__doc__,
|
|
|
1158 "get_referrers(*objs) -> list\n\
|
|
|
1159 Return the list of objects that directly refer to any of objs.");
|
|
|
1160
|
|
|
1161 static PyObject *
|
|
|
1162 gc_get_referrers(PyObject *self, PyObject *args)
|
|
|
1163 {
|
|
|
1164 int i;
|
|
|
1165 PyObject *result = PyList_New(0);
|
|
|
1166 if (!result) return NULL;
|
|
|
1167
|
|
|
1168 for (i = 0; i < NUM_GENERATIONS; i++) {
|
|
|
1169 if (!(gc_referrers_for(args, GEN_HEAD(i), result))) {
|
|
|
1170 Py_DECREF(result);
|
|
|
1171 return NULL;
|
|
|
1172 }
|
|
|
1173 }
|
|
|
1174 return result;
|
|
|
1175 }
|
|
|
1176
|
|
|
1177 /* Append obj to list; return true if error (out of memory), false if OK. */
|
|
|
1178 static int
|
|
|
1179 referentsvisit(PyObject *obj, PyObject *list)
|
|
|
1180 {
|
|
|
1181 return PyList_Append(list, obj) < 0;
|
|
|
1182 }
|
|
|
1183
|
|
|
1184 PyDoc_STRVAR(gc_get_referents__doc__,
|
|
|
1185 "get_referents(*objs) -> list\n\
|
|
|
1186 Return the list of objects that are directly referred to by objs.");
|
|
|
1187
|
|
|
1188 static PyObject *
|
|
|
1189 gc_get_referents(PyObject *self, PyObject *args)
|
|
|
1190 {
|
|
|
1191 Py_ssize_t i;
|
|
|
1192 PyObject *result = PyList_New(0);
|
|
|
1193
|
|
|
1194 if (result == NULL)
|
|
|
1195 return NULL;
|
|
|
1196
|
|
|
1197 for (i = 0; i < PyTuple_GET_SIZE(args); i++) {
|
|
|
1198 traverseproc traverse;
|
|
|
1199 PyObject *obj = PyTuple_GET_ITEM(args, i);
|
|
|
1200
|
|
|
1201 if (! PyObject_IS_GC(obj))
|
|
|
1202 continue;
|
|
|
1203 traverse = Py_TYPE(obj)->tp_traverse;
|
|
|
1204 if (! traverse)
|
|
|
1205 continue;
|
|
|
1206 if (traverse(obj, (visitproc)referentsvisit, result)) {
|
|
|
1207 Py_DECREF(result);
|
|
|
1208 return NULL;
|
|
|
1209 }
|
|
|
1210 }
|
|
|
1211 return result;
|
|
|
1212 }
|
|
|
1213
|
|
|
1214 PyDoc_STRVAR(gc_get_objects__doc__,
|
|
|
1215 "get_objects() -> [...]\n"
|
|
|
1216 "\n"
|
|
|
1217 "Return a list of objects tracked by the collector (excluding the list\n"
|
|
|
1218 "returned).\n");
|
|
|
1219
|
|
|
1220 static PyObject *
|
|
|
1221 gc_get_objects(PyObject *self, PyObject *noargs)
|
|
|
1222 {
|
|
|
1223 int i;
|
|
|
1224 PyObject* result;
|
|
|
1225
|
|
|
1226 result = PyList_New(0);
|
|
|
1227 if (result == NULL)
|
|
|
1228 return NULL;
|
|
|
1229 for (i = 0; i < NUM_GENERATIONS; i++) {
|
|
|
1230 if (append_objects(result, GEN_HEAD(i))) {
|
|
|
1231 Py_DECREF(result);
|
|
|
1232 return NULL;
|
|
|
1233 }
|
|
|
1234 }
|
|
|
1235 return result;
|
|
|
1236 }
|
|
|
1237
|
|
|
1238 PyDoc_STRVAR(gc_is_tracked__doc__,
|
|
|
1239 "is_tracked(obj) -> bool\n"
|
|
|
1240 "\n"
|
|
|
1241 "Returns true if the object is tracked by the garbage collector.\n"
|
|
|
1242 "Simple atomic objects will return false.\n"
|
|
|
1243 );
|
|
|
1244
|
|
|
1245 static PyObject *
|
|
|
1246 gc_is_tracked(PyObject *self, PyObject *obj)
|
|
|
1247 {
|
|
|
1248 PyObject *result;
|
|
|
1249
|
|
|
1250 if (PyObject_IS_GC(obj) && IS_TRACKED(obj))
|
|
|
1251 result = Py_True;
|
|
|
1252 else
|
|
|
1253 result = Py_False;
|
|
|
1254 Py_INCREF(result);
|
|
|
1255 return result;
|
|
|
1256 }
|
|
|
1257
|
|
|
1258
|
|
|
1259 PyDoc_STRVAR(gc__doc__,
|
|
|
1260 "This module provides access to the garbage collector for reference cycles.\n"
|
|
|
1261 "\n"
|
|
|
1262 "enable() -- Enable automatic garbage collection.\n"
|
|
|
1263 "disable() -- Disable automatic garbage collection.\n"
|
|
|
1264 "isenabled() -- Returns true if automatic collection is enabled.\n"
|
|
|
1265 "collect() -- Do a full collection right now.\n"
|
|
|
1266 "get_count() -- Return the current collection counts.\n"
|
|
|
1267 "set_debug() -- Set debugging flags.\n"
|
|
|
1268 "get_debug() -- Get debugging flags.\n"
|
|
|
1269 "set_threshold() -- Set the collection thresholds.\n"
|
|
|
1270 "get_threshold() -- Return the current the collection thresholds.\n"
|
|
|
1271 "get_objects() -- Return a list of all objects tracked by the collector.\n"
|
|
|
1272 "is_tracked() -- Returns true if a given object is tracked.\n"
|
|
|
1273 "get_referrers() -- Return the list of objects that refer to an object.\n"
|
|
|
1274 "get_referents() -- Return the list of objects that an object refers to.\n");
|
|
|
1275
|
|
|
1276 static PyMethodDef GcMethods[] = {
|
|
|
1277 {"enable", gc_enable, METH_NOARGS, gc_enable__doc__},
|
|
|
1278 {"disable", gc_disable, METH_NOARGS, gc_disable__doc__},
|
|
|
1279 {"isenabled", gc_isenabled, METH_NOARGS, gc_isenabled__doc__},
|
|
|
1280 {"set_debug", gc_set_debug, METH_VARARGS, gc_set_debug__doc__},
|
|
|
1281 {"get_debug", gc_get_debug, METH_NOARGS, gc_get_debug__doc__},
|
|
|
1282 {"get_count", gc_get_count, METH_NOARGS, gc_get_count__doc__},
|
|
|
1283 {"set_threshold", gc_set_thresh, METH_VARARGS, gc_set_thresh__doc__},
|
|
|
1284 {"get_threshold", gc_get_thresh, METH_NOARGS, gc_get_thresh__doc__},
|
|
|
1285 {"collect", (PyCFunction)gc_collect,
|
|
|
1286 METH_VARARGS | METH_KEYWORDS, gc_collect__doc__},
|
|
|
1287 {"get_objects", gc_get_objects,METH_NOARGS, gc_get_objects__doc__},
|
|
|
1288 {"is_tracked", gc_is_tracked, METH_O, gc_is_tracked__doc__},
|
|
|
1289 {"get_referrers", gc_get_referrers, METH_VARARGS,
|
|
|
1290 gc_get_referrers__doc__},
|
|
|
1291 {"get_referents", gc_get_referents, METH_VARARGS,
|
|
|
1292 gc_get_referents__doc__},
|
|
|
1293 {NULL, NULL} /* Sentinel */
|
|
|
1294 };
|
|
|
1295
|
|
|
1296 static struct PyModuleDef gcmodule = {
|
|
|
1297 PyModuleDef_HEAD_INIT,
|
|
|
1298 "gc", /* m_name */
|
|
|
1299 gc__doc__, /* m_doc */
|
|
|
1300 -1, /* m_size */
|
|
|
1301 GcMethods, /* m_methods */
|
|
|
1302 NULL, /* m_reload */
|
|
|
1303 NULL, /* m_traverse */
|
|
|
1304 NULL, /* m_clear */
|
|
|
1305 NULL /* m_free */
|
|
|
1306 };
|
|
|
1307
|
|
|
1308 PyMODINIT_FUNC
|
|
|
1309 PyInit_gc(void)
|
|
|
1310 {
|
|
|
1311 PyObject *m;
|
|
|
1312
|
|
|
1313 m = PyModule_Create(&gcmodule);
|
|
|
1314
|
|
|
1315 if (m == NULL)
|
|
|
1316 return NULL;
|
|
|
1317
|
|
|
1318 if (garbage == NULL) {
|
|
|
1319 garbage = PyList_New(0);
|
|
|
1320 if (garbage == NULL)
|
|
|
1321 return NULL;
|
|
|
1322 }
|
|
|
1323 Py_INCREF(garbage);
|
|
|
1324 if (PyModule_AddObject(m, "garbage", garbage) < 0)
|
|
|
1325 return NULL;
|
|
|
1326
|
|
|
1327 /* Importing can't be done in collect() because collect()
|
|
|
1328 * can be called via PyGC_Collect() in Py_Finalize().
|
|
|
1329 * This wouldn't be a problem, except that <initialized> is
|
|
|
1330 * reset to 0 before calling collect which trips up
|
|
|
1331 * the import and triggers an assertion.
|
|
|
1332 */
|
|
|
1333 if (tmod == NULL) {
|
|
|
1334 tmod = PyImport_ImportModuleNoBlock("time");
|
|
|
1335 if (tmod == NULL)
|
|
|
1336 PyErr_Clear();
|
|
|
1337 }
|
|
|
1338
|
|
|
1339 #define ADD_INT(NAME) if (PyModule_AddIntConstant(m, #NAME, NAME) < 0) return NULL
|
|
|
1340 ADD_INT(DEBUG_STATS);
|
|
|
1341 ADD_INT(DEBUG_COLLECTABLE);
|
|
|
1342 ADD_INT(DEBUG_UNCOLLECTABLE);
|
|
|
1343 ADD_INT(DEBUG_SAVEALL);
|
|
|
1344 ADD_INT(DEBUG_LEAK);
|
|
|
1345 #undef ADD_INT
|
|
|
1346 return m;
|
|
|
1347 }
|
|
|
1348
|
|
|
1349 /* API to invoke gc.collect() from C */
|
|
|
1350 Py_ssize_t
|
|
|
1351 PyGC_Collect(void)
|
|
|
1352 {
|
|
|
1353 Py_ssize_t n;
|
|
|
1354
|
|
|
1355 if (collecting)
|
|
|
1356 n = 0; /* already collecting, don't do anything */
|
|
|
1357 else {
|
|
|
1358 collecting = 1;
|
|
|
1359 n = collect(NUM_GENERATIONS - 1);
|
|
|
1360 collecting = 0;
|
|
|
1361 }
|
|
|
1362
|
|
|
1363 return n;
|
|
|
1364 }
|
|
|
1365
|
|
|
1366 void
|
|
|
1367 _PyGC_Fini(void)
|
|
|
1368 {
|
|
|
1369 if (!(debug & DEBUG_SAVEALL)
|
|
|
1370 && garbage != NULL && PyList_GET_SIZE(garbage) > 0) {
|
|
|
1371 char *message;
|
|
|
1372 if (debug & DEBUG_UNCOLLECTABLE)
|
|
|
1373 message = "gc: %zd uncollectable objects at " \
|
|
|
1374 "shutdown";
|
|
|
1375 else
|
|
|
1376 message = "gc: %zd uncollectable objects at " \
|
|
|
1377 "shutdown; use gc.set_debug(gc.DEBUG_UNCOLLECTABLE) to list them";
|
|
|
1378 if (PyErr_WarnFormat(PyExc_ResourceWarning, 0, message,
|
|
|
1379 PyList_GET_SIZE(garbage)) < 0)
|
|
|
1380 PyErr_WriteUnraisable(NULL);
|
|
|
1381 if (debug & DEBUG_UNCOLLECTABLE) {
|
|
|
1382 PyObject *repr = NULL, *bytes = NULL;
|
|
|
1383 repr = PyObject_Repr(garbage);
|
|
|
1384 if (!repr || !(bytes = PyUnicode_EncodeFSDefault(repr)))
|
|
|
1385 PyErr_WriteUnraisable(garbage);
|
|
|
1386 else {
|
|
|
1387 PySys_WriteStderr(
|
|
|
1388 " %s\n",
|
|
|
1389 PyBytes_AS_STRING(bytes)
|
|
|
1390 );
|
|
|
1391 }
|
|
|
1392 Py_XDECREF(repr);
|
|
|
1393 Py_XDECREF(bytes);
|
|
|
1394 }
|
|
|
1395 }
|
|
|
1396 }
|
|
|
1397
|
|
|
1398 /* for debugging */
|
|
|
1399 void
|
|
|
1400 _PyGC_Dump(PyGC_Head *g)
|
|
|
1401 {
|
|
|
1402 _PyObject_Dump(FROM_GC(g));
|
|
|
1403 }
|
|
|
1404
|
|
|
1405 /* extension modules might be compiled with GC support so these
|
|
|
1406 functions must always be available */
|
|
|
1407
|
|
|
1408 #undef PyObject_GC_Track
|
|
|
1409 #undef PyObject_GC_UnTrack
|
|
|
1410 #undef PyObject_GC_Del
|
|
|
1411 #undef _PyObject_GC_Malloc
|
|
|
1412
|
|
|
1413 void
|
|
|
1414 PyObject_GC_Track(void *op)
|
|
|
1415 {
|
|
|
1416 _PyObject_GC_TRACK(op);
|
|
|
1417 }
|
|
|
1418
|
|
|
1419 /* for binary compatibility with 2.2 */
|
|
|
1420 void
|
|
|
1421 _PyObject_GC_Track(PyObject *op)
|
|
|
1422 {
|
|
|
1423 PyObject_GC_Track(op);
|
|
|
1424 }
|
|
|
1425
|
|
|
1426 void
|
|
|
1427 PyObject_GC_UnTrack(void *op)
|
|
|
1428 {
|
|
|
1429 /* Obscure: the Py_TRASHCAN mechanism requires that we be able to
|
|
|
1430 * call PyObject_GC_UnTrack twice on an object.
|
|
|
1431 */
|
|
|
1432 if (IS_TRACKED(op))
|
|
|
1433 _PyObject_GC_UNTRACK(op);
|
|
|
1434 }
|
|
|
1435
|
|
|
1436 /* for binary compatibility with 2.2 */
|
|
|
1437 void
|
|
|
1438 _PyObject_GC_UnTrack(PyObject *op)
|
|
|
1439 {
|
|
|
1440 PyObject_GC_UnTrack(op);
|
|
|
1441 }
|
|
|
1442
|
|
|
1443 PyObject *
|
|
|
1444 _PyObject_GC_Malloc(size_t basicsize)
|
|
|
1445 {
|
|
|
1446 PyObject *op;
|
|
|
1447 PyGC_Head *g;
|
|
|
1448 if (basicsize > PY_SSIZE_T_MAX - sizeof(PyGC_Head))
|
|
|
1449 return PyErr_NoMemory();
|
|
|
1450 g = (PyGC_Head *)PyObject_MALLOC(
|
|
|
1451 sizeof(PyGC_Head) + basicsize);
|
|
|
1452 if (g == NULL)
|
|
|
1453 return PyErr_NoMemory();
|
|
|
1454 g->gc.gc_refs = GC_UNTRACKED;
|
|
|
1455 generations[0].count++; /* number of allocated GC objects */
|
|
|
1456 if (generations[0].count > generations[0].threshold &&
|
|
|
1457 enabled &&
|
|
|
1458 generations[0].threshold &&
|
|
|
1459 !collecting &&
|
|
|
1460 !PyErr_Occurred()) {
|
|
|
1461 collecting = 1;
|
|
|
1462 collect_generations();
|
|
|
1463 collecting = 0;
|
|
|
1464 }
|
|
|
1465 op = FROM_GC(g);
|
|
|
1466 return op;
|
|
|
1467 }
|
|
|
1468
|
|
|
1469 PyObject *
|
|
|
1470 _PyObject_GC_New(PyTypeObject *tp)
|
|
|
1471 {
|
|
|
1472 PyObject *op = _PyObject_GC_Malloc(_PyObject_SIZE(tp));
|
|
|
1473 if (op != NULL)
|
|
|
1474 op = PyObject_INIT(op, tp);
|
|
|
1475 return op;
|
|
|
1476 }
|
|
|
1477
|
|
|
1478 PyVarObject *
|
|
|
1479 _PyObject_GC_NewVar(PyTypeObject *tp, Py_ssize_t nitems)
|
|
|
1480 {
|
|
|
1481 const size_t size = _PyObject_VAR_SIZE(tp, nitems);
|
|
|
1482 PyVarObject *op = (PyVarObject *) _PyObject_GC_Malloc(size);
|
|
|
1483 if (op != NULL)
|
|
|
1484 op = PyObject_INIT_VAR(op, tp, nitems);
|
|
|
1485 return op;
|
|
|
1486 }
|
|
|
1487
|
|
|
1488 PyVarObject *
|
|
|
1489 _PyObject_GC_Resize(PyVarObject *op, Py_ssize_t nitems)
|
|
|
1490 {
|
|
|
1491 const size_t basicsize = _PyObject_VAR_SIZE(Py_TYPE(op), nitems);
|
|
|
1492 PyGC_Head *g = AS_GC(op);
|
|
|
1493 if (basicsize > PY_SSIZE_T_MAX - sizeof(PyGC_Head))
|
|
|
1494 return (PyVarObject *)PyErr_NoMemory();
|
|
|
1495 g = (PyGC_Head *)PyObject_REALLOC(g, sizeof(PyGC_Head) + basicsize);
|
|
|
1496 if (g == NULL)
|
|
|
1497 return (PyVarObject *)PyErr_NoMemory();
|
|
|
1498 op = (PyVarObject *) FROM_GC(g);
|
|
|
1499 Py_SIZE(op) = nitems;
|
|
|
1500 return op;
|
|
|
1501 }
|
|
|
1502
|
|
|
1503 void
|
|
|
1504 PyObject_GC_Del(void *op)
|
|
|
1505 {
|
|
|
1506 PyGC_Head *g = AS_GC(op);
|
|
|
1507 if (IS_TRACKED(op))
|
|
|
1508 gc_list_remove(g);
|
|
|
1509 if (generations[0].count > 0) {
|
|
|
1510 generations[0].count--;
|
|
|
1511 }
|
|
|
1512 PyObject_FREE(g);
|
|
|
1513 }
|
