1 | """
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2 | oil_gdb.py
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3 |
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4 | https://fy.blackhats.net.au/blog/html/2017/08/04/so_you_want_to_script_gdb_with_python.html
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5 | """
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6 | from __future__ import print_function
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7 |
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8 | import struct
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9 |
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10 | import gdb
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11 |
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12 | class SimpleCommand(gdb.Command):
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13 | """Test command."""
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14 | def __init__(self):
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15 | # This registers our class as "simple_command"
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16 | super(SimpleCommand, self).__init__("simple_command", gdb.COMMAND_DATA)
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17 |
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18 | def invoke(self, arg, from_tty):
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19 | # When we call "simple_command" from gdb, this is the method
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20 | # that will be called.
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21 | print("Hello from simple_command!")
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22 |
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23 | # This registers our class to the gdb runtime at "source" time.
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24 | SimpleCommand()
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25 |
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26 |
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27 | # Following:
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28 | # https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/developer_guide/debuggingprettyprinters
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29 |
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30 | class StrPrinter:
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31 | """Print the Str* type from mycpp/mylib."""
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32 |
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33 | def __init__(self, val):
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34 | self.val = val
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35 |
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36 | def to_string(self):
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37 | len_ = self.val['len_']
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38 |
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39 | # This is a gdb.Value object
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40 | data_ = self.val['data_']
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41 |
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42 | # Make a lazystring out of it
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43 | # https://sourceware.org/gdb/current/onlinedocs/gdb/Values-From-Inferior.html
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44 | # TODO: could try utf-8 too
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45 | return data_.lazy_string('ascii', len_)
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46 |
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47 |
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48 | class GcStrPrinter:
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49 | """Print Str type"""
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50 |
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51 | def __init__(self, val):
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52 | self.val = val
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53 |
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54 | def to_string(self):
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55 | # Unused because GDB in CLion doesn't want us to print past end of array?
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56 | len_ = self.val['obj_len_'] - 12 - 1
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57 |
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58 | # This is a gdb.Value object
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59 | data_ = self.val['data_']
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60 |
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61 | # This only prints until first NUL, since we don't have the length.
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62 | # note: lazy_string() only prints the first char!
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63 | t = gdb.lookup_type('char').pointer()
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64 | return data_.reinterpret_cast(t)
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65 |
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66 |
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67 | class AsdlPrinter(object):
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68 | """Print the variants of a particular ASDL sum type.
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69 |
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70 | This looks at the tag in memory and casts the "super" sum type to the
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71 | variant type.
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72 |
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73 | It uses the children() method to return a tree structure.
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74 | """
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75 | def __init__(self, val, variants):
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76 | self.val = val
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77 | self.variants = variants
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78 | self.asdl_tag = None
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79 |
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80 | # This doesn't seem to make a difference
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81 | #def display_hint(self):
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82 | # return 'map'
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83 |
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84 | def _GetTag(self):
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85 | """Helper for .children() and .to_string().
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86 |
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87 | We don't know the order in which they'll be called.
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88 | """
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89 | if self.asdl_tag is None:
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90 | # Get address of value and look at first 16 bits
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91 | obj = self.val.dereference() # location of part_value_t
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92 |
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93 | # Read the uint16_t tag
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94 | tag_mem = gdb.selected_inferior().read_memory(obj.address, 2)
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95 |
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96 | # Unpack 2 bytes into an integer
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97 | (self.asdl_tag,) = struct.unpack('H', tag_mem)
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98 |
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99 | return self.asdl_tag
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100 |
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101 | def children(self):
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102 | tag = self._GetTag()
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103 |
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104 | if tag in self.variants:
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105 | value_type = gdb.lookup_type(self.variants[tag])
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106 | else:
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107 | #pprint(self.variants)
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108 | raise AssertionError('Invalid tag %d' % tag)
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109 |
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110 | sub_val = self.val.cast(value_type.pointer())
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111 |
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112 | # TODO: I want to also print the tag here, e.g. part_value.String
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113 |
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114 | #print('type %s' % value_type.name)
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115 | #print('fields %s' % value_type.fields())
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116 |
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117 | for field in value_type.fields():
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118 | if not field.is_base_class:
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119 | #print('field %s' % field.name)
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120 |
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121 | # TODO: special case for the 'tag' field
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122 | # e.g. turn 1005 -> word_part.SimpleVarSub, etc.
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123 | yield field.name, sub_val[field]
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124 |
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125 | def to_string(self):
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126 | tag = self._GetTag()
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127 |
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128 | #return 'ZZ ' + self.variants.get(tag)
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129 |
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130 | # Show the variant type name, not the sum type name
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131 | # Note: GDB 'print' displays this prefix, but it Eclipse doesn't appear
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132 | # to.
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133 | return self.variants.get(tag)
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134 |
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135 |
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136 | class TypeLookup(object):
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137 | """Return a custom pretty printer based on GDB type information."""
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138 |
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139 | def __init__(self, sum_type_lookup):
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140 | self.sum_type_lookup = sum_type_lookup
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141 |
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142 | def __call__(self, val):
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143 | # TODO:
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144 | # - Tuple{2,3,4} (may be a value, not a pointer)
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145 | # - Dict*
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146 |
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147 | typ = val.type
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148 | # Str*, etc.
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149 | if typ.code == gdb.TYPE_CODE_PTR:
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150 | target = typ.target()
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151 | #print('target %s' % target)
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152 | #print('target name %r' % target.name)
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153 | #print('target tag %r' % target.tag)
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154 |
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155 | if target.name == 'Str':
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156 | return GcStrPrinter(val)
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157 |
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158 | if target.name in self.sum_type_lookup:
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159 | return AsdlPrinter(val, self.sum_type_lookup[target.name])
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160 |
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161 | return None
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162 |
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163 |
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164 | def Preprocess(t):
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165 | """
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166 | Take a list of raw dicts from the ASDL compiler and make a single dict that
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167 | TypeLookup() can use.
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168 |
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169 | Note: technically this could be done at build time.
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170 | """
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171 | type_lookup = {}
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172 | for (cpp_namespace, tags_to_types) in t:
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173 | for sum_name, d in tags_to_types.items():
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174 | d2 = {}
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175 | for tag, type_name in d.items():
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176 | d2[tag] = '%s::%s' % (cpp_namespace, type_name)
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177 | type_lookup['%s::%s' % (cpp_namespace, sum_name)] = d2
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178 | return type_lookup
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179 |
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180 |
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181 | # Each of these files defines two variables. We append them to a global list.
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182 | asdl_types = []
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183 | gdb.execute('source _devbuild/gen/syntax_asdl_debug.py')
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184 | asdl_types.append((cpp_namespace, tags_to_types))
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185 | gdb.execute('source _devbuild/gen/runtime_asdl_debug.py')
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186 | asdl_types.append((cpp_namespace, tags_to_types))
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187 |
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188 | sum_type_lookup = Preprocess(asdl_types)
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189 |
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190 | #from pprint import pprint
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191 | #pprint(type_lookup)
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192 |
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193 |
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194 | gdb.pretty_printers.append(TypeLookup(sum_type_lookup))
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