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111
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1 /* go-fieldtrack.c -- structure field data analysis.
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2
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3 Copyright 2012 The Go Authors. All rights reserved.
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4 Use of this source code is governed by a BSD-style
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5 license that can be found in the LICENSE file. */
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6
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7 #include "runtime.h"
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8
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9 /* The compiler will track fields that have the tag go:"track". Any
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10 function that refers to such a field will call this function with a
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11 string
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12 fieldtrack "package.type.field"
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13
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14 This function does not actually do anything. Instead, we gather
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15 the field tracking information by looking for strings of that form
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16 in the read-only data section. This is, of course, a horrible
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17 hack, but it's good enough for now. We can improve it, e.g., by a
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18 linker plugin, if this turns out to be useful. */
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19
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20 void
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21 __go_fieldtrack (byte *p __attribute__ ((unused)))
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22 {
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23 }
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24
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25 /* A runtime function to add all the tracked fields to a
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26 map[string]bool. */
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27
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145
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28 extern void *mapassign (const struct maptype *, void *hmap, const void *key)
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29 __asm__ (GOSYM_PREFIX "runtime.mapassign");
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30
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31 // The type descriptor for map[string] bool. */
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131
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32 extern const char map_string_bool[] __attribute__ ((weak));
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33 extern const char map_string_bool[]
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34 __asm__ (GOSYM_PREFIX "type..map.6string.7bool");
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111
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35
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36 void runtime_Fieldtrack (void *) __asm__ (GOSYM_PREFIX "runtime.Fieldtrack");
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37
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38 void
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39 runtime_Fieldtrack (void *m)
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40 {
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41 const char *p;
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42 const char *pend;
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43 const char *prefix;
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44 size_t prefix_len;
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45
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46 if (map_string_bool == NULL)
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47 return;
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48
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49 p = __data_start;
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50 if (p == NULL)
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51 p = __etext;
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52 if (p == NULL)
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53 p = _etext;
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54 if (p == NULL)
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55 return;
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56
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57 pend = __edata;
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58 if (pend == NULL)
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59 pend = _edata;
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60 if (pend == NULL)
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61 pend = __bss_start;
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62 if (pend == NULL)
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63 return;
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64
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65 prefix = "fieldtrack ";
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66 prefix_len = __builtin_strlen (prefix);
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67
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68 while (p < pend)
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69 {
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70 const char *q1;
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71 const char *q2;
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72
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73 q1 = __builtin_memchr (p + prefix_len, '"', pend - (p + prefix_len));
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74 if (q1 == NULL)
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75 break;
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76
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77 if (__builtin_memcmp (q1 - prefix_len, prefix, prefix_len) != 0)
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78 {
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79 p = q1 + 1;
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80 continue;
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81 }
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82
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83 q1++;
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84 q2 = __builtin_memchr (q1, '"', pend - q1);
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85 if (q2 == NULL)
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86 break;
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87
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88 if (__builtin_memchr (q1, '\0', q2 - q1) == NULL)
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89 {
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90 String s;
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91 void *p;
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92
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93 s.str = (const byte *) q1;
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94 s.len = q2 - q1;
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131
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95 p = mapassign((const void*) map_string_bool, m, &s);
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111
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96 *(_Bool*)p = 1;
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97 }
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98
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99 p = q2;
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100 }
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101 }
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