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Matheus Marchini
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tools: add debug symbols for node internals
Before these changes, only V8 added debug symbols to Node's binary, limiting the possibilities for debugger's developers to add some features that rely on investigating Node's internal structures. These changes are a first steps towards empowering debug tools to navigate Node's internals strucutres. One example of what can be achieved with this is shown at nodejs/llnode#122 (a command which prints information about handles and requests on the queue for a core dump file). Node debug symbols are prefixed with node_dbg_. Ref: nodejs/llnode#122 Ref: nodejs/post-mortem#46
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2 files changed

Lines changed: 224 additions & 1 deletion

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‎node.gyp‎

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# node.gyp is added to the project by default.
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'common.gypi',
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'<(SHARED_INTERMEDIATE_DIR)/node_javascript.cc',
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'<(SHARED_INTERMEDIATE_DIR)/node-debug-support.cc',
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],
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'variables': {
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}]]
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}],
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]
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}
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},
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{
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'target_name': 'node_postmortem_metadata',
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'type': 'none',
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'toolsets': ['host'],
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'actions': [
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{
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'action_name': 'gen-postmortem-metadata',
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'process_outputs_as_sources': 1,
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'inputs': [
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'./tools/gen-postmortem-metadata.py',
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],
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'outputs': [
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'<(SHARED_INTERMEDIATE_DIR)/node-debug-support.cc',
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],
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'action': [
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'python',
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'./tools/gen-postmortem-metadata.py',
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'<@(_outputs)',
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]
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}
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]
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},
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], # end targets
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'conditions': [

‎tools/gen-postmortem-metadata.py‎

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#!/usr/bin/env python
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#
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# gen-postmortem-metadata.py output_file.cc
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#
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# Creates debugging symbols to help naviage Node's internals using post-mortem
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# debugging tools.
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#
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import os
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import fnmatch
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import re
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from glob import glob
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import sys
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class DebugSymbol(object):
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type_ = 'int'
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_prefix = 'nodedbg_'
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def __init__(self, name, value, headers=[], type_=None):
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self.name = name
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self.value = value
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self.headers = headers
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self.type_ = type_ or DebugSymbol.type_
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@classmethod
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def get_headers(cls, debug_symbols):
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'''
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Return a list of headers without duplicates, preserving the order they were
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declared
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'''
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seen = set()
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headers = [debug_symbol.headers for debug_symbol in debug_symbols]
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headers = sum(headers, [])
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result = []
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for h in headers:
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if not h in seen:
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seen.add(h)
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result.append(h)
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return result
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@property
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def declare(self):
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return '{type} {prefix}{name};'.format(
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type=self.type_,
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prefix=self._prefix,
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name=self.name,
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)
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@property
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def fill(self):
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return '{prefix}{name} = {value};'.format(
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prefix=self._prefix,
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name=self.name,
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value=self.value,
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)
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debug_symbols = [
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DebugSymbol(
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name='environment_context_idx_embedder_data',
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value='Environment::kContextEmbedderDataIndex',
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headers=['env.h'],
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type_='int',
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),
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DebugSymbol(
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name='class__BaseObject__persistent_handle',
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value='nonstandard_offsetof(BaseObject, persistent_handle_)',
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headers=['base_object-inl.h'],
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type_='size_t',
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),
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DebugSymbol(
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name='class__Environment__handleWrapQueue',
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value='nonstandard_offsetof(Environment, handle_wrap_queue_)',
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headers=['env.h'],
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type_='size_t',
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),
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DebugSymbol(
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name='class__HandleWrap__node',
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value='nonstandard_offsetof(HandleWrap, handle_wrap_queue_)',
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headers=['handle_wrap.h'],
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type_='size_t',
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),
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DebugSymbol(
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name='class__HandleWrapQueue__headOffset',
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value='offsetof(Environment::HandleWrapQueue, head_)',
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headers=['env.h'],
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type_='size_t',
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),
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DebugSymbol(
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name='class__HandleWrapQueue__nextOffset',
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value='offsetof(ListNode<HandleWrap>, next_)',
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headers=['handle_wrap.h', 'util.h'],
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type_='size_t',
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),
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DebugSymbol(
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name='class__Environment__reqWrapQueue',
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value='nonstandard_offsetof(Environment, req_wrap_queue_)',
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headers=['env.h'],
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type_='size_t',
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),
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DebugSymbol(
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name='class__ReqWrap__node',
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value='nonstandard_offsetof(ReqWrap<uv_req_t>, req_wrap_queue_)',
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headers=['req_wrap.h'],
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type_='size_t',
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),
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DebugSymbol(
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name='class__ReqWrapQueue__headOffset',
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value='offsetof(Environment::ReqWrapQueue, head_)',
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headers=['env.h'],
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type_='size_t',
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),
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DebugSymbol(
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name='class__ReqWrapQueue__nextOffset',
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value='offsetof(ListNode<ReqWrap<uv_req_t>>, next_)',
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headers=['req_wrap.h', 'util.h'],
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type_='size_t',
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),
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]
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template = '''
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/*
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* This file is generated by {filename}. Do not edit directly.
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*/
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// Need to import standard headers before redefining private, otherwise it
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// won't compile
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{standard_includes}
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int GenDebugSymbol();
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#define private friend int GenDebugSymbol(); private
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#define nonstandard_offsetof(CLASS, FIELD) reinterpret_cast<uintptr_t>\
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(&(static_cast<CLASS*>(0)->FIELD))
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{includes}
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{declare_symbols}
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namespace node {{
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int GenDebugSymbol() {{
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{fill_symbols}
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return 1;
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}}
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int debug_symbols_generated = GenDebugSymbol();
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}}
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'''
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def get_standard_includes():
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'''
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Try to find all standard C++ headers needed by node and its dependencies
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'''
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includes = ["algorithm", "array", "atomic", "bitset", "cctype", "climits",
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"cmath", "cstdarg", "cstddef", "cstdint", "cstdio", "cstdlib", "cstring",
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"ctime", "deque", "exception", "forward_list", "fstream", "functional",
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"iomanip", "iosfwd", "iostream", "istream", "iterator", "limits", "list",
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"map", "memory", "new", "ostream", "queue", "set", "sstream", "stack",
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"streambuf", "string", "tuple", "type_traits", "typeinfo", "unordered_map",
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"unordered_set", "utility", "vector"]
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return includes
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def create_symbols_file():
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out = file(sys.argv[1], 'w')
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headers = DebugSymbol.get_headers(debug_symbols)
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includes = ['#include "{0}"'.format(header) for header in headers]
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includes = '\n'.join(includes)
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standard_includes = get_standard_includes()
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standard_includes = ['#include <{0}>'.format(include) for include in standard_includes]
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standard_includes = '\n'.join(standard_includes)
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declare_symbols = '\n'.join([symbol.declare for symbol in debug_symbols])
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fill_symbols = '\n'.join([symbol.fill for symbol in debug_symbols])
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out.write(template.format(
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filename=sys.argv[0],
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includes=includes,
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standard_includes=standard_includes,
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declare_symbols=declare_symbols,
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fill_symbols=fill_symbols,
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))
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if len(sys.argv) < 2:
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print('usage: {0} output.cc'.format(sys.argv[0]))
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sys.exit(2)
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create_symbols_file()

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