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61e22cd85c
It is now possible to load object files and scan over sections, symbols, and relocations! Includes test code with partial coverage. git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@152482 91177308-0d34-0410-b5e6-96231b3b80d8
524 lines
16 KiB
Python
524 lines
16 KiB
Python
#===- object.py - Python Object Bindings --------------------*- python -*--===#
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#
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# The LLVM Compiler Infrastructure
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#
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# This file is distributed under the University of Illinois Open Source
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# License. See LICENSE.TXT for details.
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#
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#===------------------------------------------------------------------------===#
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r"""
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Object File Interface
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=====================
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This module provides an interface for reading information from object files
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(e.g. binary executables and libraries).
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Using this module, you can obtain information about an object file's sections,
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symbols, and relocations. These are represented by the classes ObjectFile,
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Section, Symbol, and Relocation, respectively.
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Usage
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-----
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The only way to use this module is to start by creating an ObjectFile. You can
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create an ObjectFile by loading a file (specified by its path) or by creating a
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llvm.core.MemoryBuffer and loading that.
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Once you have an object file, you can inspect its sections and symbols directly
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by calling get_sections() and get_symbols() respectively. To inspect
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relocations, call get_relocations() on a Section instance.
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Iterator Interface
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------------------
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The LLVM bindings expose iteration over sections, symbols, and relocations in a
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way that only allows one instance to be operated on at a single time. This is
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slightly annoying from a Python perspective, as it isn't very Pythonic to have
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objects that "expire" but are still active from a dynamic language.
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To aid working around this limitation, each Section, Symbol, and Relocation
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instance caches its properties after first access. So, if the underlying
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iterator is advanced, the properties can still be obtained provided they have
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already been retrieved.
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In addition, we also provide a "cache" method on each class to cache all
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available data. You can call this on each obtained instance. Or, you can pass
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cache=True to the appropriate get_XXX() method to have this done for you.
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Here are some examples on how to perform iteration:
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obj = ObjectFile(filename='/bin/ls')
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# This is OK. Each Section is only accessed inside its own iteration slot.
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section_names = []
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for section in obj.get_sections():
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section_names.append(section.name)
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# This is NOT OK. You perform a lookup after the object has expired.
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symbols = list(obj.get_symbols())
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for symbol in symbols:
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print symbol.name # This raises because the object has expired.
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# In this example, we mix a working and failing scenario.
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symbols = []
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for symbol in obj.get_symbols():
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symbols.append(symbol)
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print symbol.name
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for symbol in symbols:
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print symbol.name # OK
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print symbol.address # NOT OK. We didn't look up this property before.
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# Cache everything up front.
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symbols = list(obj.get_symbols(cache=True))
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for symbol in symbols:
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print symbol.name # OK
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"""
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from ctypes import c_char_p
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from ctypes import c_uint64
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from .common import CachedProperty
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from .common import LLVMObject
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from .common import c_object_p
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from .common import get_library
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from .core import MemoryBuffer
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__all__ = [
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"lib",
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"ObjectFile",
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"Relocation",
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"Section",
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"Symbol",
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]
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class ObjectFile(LLVMObject):
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"""Represents an object/binary file."""
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def __init__(self, filename=None, contents=None):
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"""Construct an instance from a filename or binary data.
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filename must be a path to a file that can be opened with open().
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contents can be either a native Python buffer type (like str) or a
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llvm.core.MemoryBuffer instance.
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"""
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if contents:
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assert isinstance(contents, MemoryBuffer)
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if filename is not None:
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contents = MemoryBuffer(filename=filename)
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if contents is None:
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raise Exception('No input found.')
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ptr = lib.LLVMCreateObjectFile(contents)
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LLVMObject.__init__(self, ptr, disposer=lib.LLVMDisposeObjectFile)
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self.take_ownership(contents)
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def get_sections(self, cache=False):
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"""Obtain the sections in this object file.
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This is a generator for llvm.object.Section instances.
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Sections are exposed as limited-use objects. See the module's
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documentation on iterators for more.
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"""
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sections = lib.LLVMGetSections(self)
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last = None
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while True:
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if lib.LLVMIsSectionIteratorAtEnd(self, sections):
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break
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last = Section(sections)
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if cache:
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last.cache()
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yield last
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lib.LLVMMoveToNextSection(sections)
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last.expire()
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if last is not None:
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last.expire()
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lib.LLVMDisposeSectionIterator(sections)
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def get_symbols(self, cache=False):
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"""Obtain the symbols in this object file.
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This is a generator for llvm.object.Symbol instances.
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Each Symbol instance is a limited-use object. See this module's
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documentation on iterators for more.
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"""
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symbols = lib.LLVMGetSymbols(self)
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last = None
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while True:
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if lib.LLVMIsSymbolIteratorAtEnd(self, symbols):
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break
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last = Symbol(symbols, self)
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if cache:
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last.cache()
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yield last
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lib.LLVMMoveToNextSymbol(symbols)
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last.expire()
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if last is not None:
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last.expire()
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lib.LLVMDisposeSymbolIterator(symbols)
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class Section(LLVMObject):
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"""Represents a section in an object file."""
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def __init__(self, ptr):
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"""Construct a new section instance.
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Section instances can currently only be created from an ObjectFile
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instance. Therefore, this constructor should not be used outside of
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this module.
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"""
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LLVMObject.__init__(self, ptr)
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self.expired = False
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@CachedProperty
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def name(self):
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"""Obtain the string name of the section.
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This is typically something like '.dynsym' or '.rodata'.
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"""
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if self.expired:
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raise Exception('Section instance has expired.')
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return lib.LLVMGetSectionName(self)
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@CachedProperty
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def size(self):
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"""The size of the section, in long bytes."""
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if self.expired:
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raise Exception('Section instance has expired.')
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return lib.LLVMGetSectionSize(self)
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@CachedProperty
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def contents(self):
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if self.expired:
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raise Exception('Section instance has expired.')
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return lib.LLVMGetSectionContents(self)
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@CachedProperty
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def address(self):
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"""The address of this section, in long bytes."""
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if self.expired:
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raise Exception('Section instance has expired.')
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return lib.LLVMGetSectionAddress(self)
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def has_symbol(self, symbol):
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"""Returns whether a Symbol instance is present in this Section."""
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if self.expired:
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raise Exception('Section instance has expired.')
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assert isinstance(symbol, Symbol)
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return lib.LLVMGetSectionContainsSymbol(self, symbol)
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def get_relocations(self, cache=False):
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"""Obtain the relocations in this Section.
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This is a generator for llvm.object.Relocation instances.
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Each instance is a limited used object. See this module's documentation
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on iterators for more.
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"""
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if self.expired:
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raise Exception('Section instance has expired.')
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relocations = lib.LLVMGetRelocations(self)
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last = None
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while True:
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if lib.LLVMIsRelocationIteratorAtEnd(self, relocations):
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break
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last = Relocation(relocations)
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if cache:
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last.cache()
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yield last
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lib.LLVMMoveToNextRelocation(relocations)
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last.expire()
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if last is not None:
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last.expire()
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lib.LLVMDisposeRelocationIterator(relocations)
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def cache(self):
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"""Cache properties of this Section.
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This can be called as a workaround to the single active Section
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limitation. When called, the properties of the Section are fetched so
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they are still available after the Section has been marked inactive.
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"""
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getattr(self, 'name')
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getattr(self, 'size')
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getattr(self, 'contents')
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getattr(self, 'address')
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def expire(self):
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"""Expire the section.
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This is called internally by the section iterator.
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"""
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self.expired = True
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class Symbol(LLVMObject):
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"""Represents a symbol in an object file."""
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def __init__(self, ptr, object_file):
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assert isinstance(ptr, c_object_p)
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assert isinstance(object_file, ObjectFile)
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LLVMObject.__init__(self, ptr)
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self.expired = False
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self._object_file = object_file
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@CachedProperty
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def name(self):
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"""The str name of the symbol.
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This is often a function or variable name. Keep in mind that name
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mangling could be in effect.
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"""
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if self.expired:
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raise Exception('Symbol instance has expired.')
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return lib.LLVMGetSymbolName(self)
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@CachedProperty
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def address(self):
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"""The address of this symbol, in long bytes."""
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if self.expired:
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raise Exception('Symbol instance has expired.')
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return lib.LLVMGetSymbolAddress(self)
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@CachedProperty
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def file_offset(self):
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"""The offset of this symbol in the file, in long bytes."""
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if self.expired:
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raise Exception('Symbol instance has expired.')
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return lib.LLVMGetSymbolFileOffset(self)
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@CachedProperty
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def size(self):
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"""The size of the symbol, in long bytes."""
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if self.expired:
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raise Exception('Symbol instance has expired.')
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return lib.LLVMGetSymbolSize(self)
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@CachedProperty
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def section(self):
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"""The Section to which this Symbol belongs.
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The returned Section instance does not expire, unlike Sections that are
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commonly obtained through iteration.
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Because this obtains a new section iterator each time it is accessed,
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calling this on a number of Symbol instances could be expensive.
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"""
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sections = lib.LLVMGetSections(self._object_file)
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lib.LLVMMoveToContainingSection(sections, self)
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return Section(sections)
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def cache(self):
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"""Cache all cacheable properties."""
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getattr(self, 'name')
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getattr(self, 'address')
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getattr(self, 'file_offset')
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getattr(self, 'size')
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def expire(self):
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"""Mark the object as expired to prevent future API accesses.
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This is called internally by this module and it is unlikely that
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external callers have a legitimate reason for using it.
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"""
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self.expired = True
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class Relocation(LLVMObject):
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"""Represents a relocation definition."""
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def __init__(self, ptr):
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"""Create a new relocation instance.
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Relocations are created from objects derived from Section instances.
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Therefore, this constructor should not be called outside of this
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module. See Section.get_relocations() for the proper method to obtain
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a Relocation instance.
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"""
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assert isinstance(ptr, c_object_p)
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LLVMObject.__init__(self, ptr)
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self.expired = False
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@CachedProperty
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def address(self):
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"""The address of this relocation, in long bytes."""
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if self.expired:
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raise Exception('Relocation instance has expired.')
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return lib.LLVMGetRelocationAddress(self)
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@CachedProperty
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def offset(self):
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"""The offset of this relocation, in long bytes."""
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if self.expired:
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raise Exception('Relocation instance has expired.')
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return lib.LLVMGetRelocationOffset(self)
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@CachedProperty
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def symbol(self):
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"""The Symbol corresponding to this Relocation."""
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if self.expired:
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raise Exception('Relocation instance has expired.')
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ptr = lib.LLVMGetRelocationSymbol(self)
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return Symbol(ptr)
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@CachedProperty
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def type_number(self):
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"""The relocation type, as a long."""
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if self.expired:
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raise Exception('Relocation instance has expired.')
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return lib.LLVMGetRelocationType(self)
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@CachedProperty
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def type_name(self):
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"""The relocation type's name, as a str."""
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if self.expired:
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raise Exception('Relocation instance has expired.')
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return lib.LLVMGetRelocationTypeName(self)
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@CachedProperty
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def value_string(self):
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if self.expired:
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raise Exception('Relocation instance has expired.')
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return lib.LLVMGetRelocationValueString(self)
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def expire(self):
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"""Expire this instance, making future API accesses fail."""
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self.expired = True
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def cache(self):
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"""Cache all cacheable properties on this instance."""
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getattr(self, 'address')
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getattr(self, 'offset')
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getattr(self, 'symbol')
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getattr(self, 'type')
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getattr(self, 'type_name')
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getattr(self, 'value_string')
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def register_library(library):
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"""Register function prototypes with LLVM library instance."""
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# Object.h functions
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library.LLVMCreateObjectFile.argtypes = [MemoryBuffer]
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library.LLVMCreateObjectFile.restype = c_object_p
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library.LLVMDisposeObjectFile.argtypes = [ObjectFile]
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library.LLVMGetSections.argtypes = [ObjectFile]
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library.LLVMGetSections.restype = c_object_p
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library.LLVMDisposeSectionIterator.argtypes = [c_object_p]
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library.LLVMIsSectionIteratorAtEnd.argtypes = [ObjectFile, c_object_p]
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library.LLVMIsSectionIteratorAtEnd.restype = bool
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library.LLVMMoveToNextSection.argtypes = [c_object_p]
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library.LLVMMoveToContainingSection.argtypes = [c_object_p, c_object_p]
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library.LLVMGetSymbols.argtypes = [ObjectFile]
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library.LLVMGetSymbols.restype = c_object_p
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library.LLVMDisposeSymbolIterator.argtypes = [c_object_p]
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library.LLVMIsSymbolIteratorAtEnd.argtypes = [ObjectFile, c_object_p]
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library.LLVMIsSymbolIteratorAtEnd.restype = bool
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library.LLVMMoveToNextSymbol.argtypes = [c_object_p]
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library.LLVMGetSectionName.argtypes = [c_object_p]
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library.LLVMGetSectionName.restype = c_char_p
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library.LLVMGetSectionSize.argtypes = [c_object_p]
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library.LLVMGetSectionSize.restype = c_uint64
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library.LLVMGetSectionContents.argtypes = [c_object_p]
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library.LLVMGetSectionContents.restype = c_char_p
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library.LLVMGetSectionAddress.argtypes = [c_object_p]
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library.LLVMGetSectionAddress.restype = c_uint64
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library.LLVMGetSectionContainsSymbol.argtypes = [c_object_p, c_object_p]
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library.LLVMGetSectionContainsSymbol.restype = bool
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library.LLVMGetRelocations.argtypes = [c_object_p]
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library.LLVMGetRelocations.restype = c_object_p
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library.LLVMDisposeRelocationIterator.argtypes = [c_object_p]
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library.LLVMIsRelocationIteratorAtEnd.argtypes = [c_object_p, c_object_p]
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library.LLVMIsRelocationIteratorAtEnd.restype = bool
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library.LLVMMoveToNextRelocation.argtypes = [c_object_p]
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library.LLVMGetSymbolName.argtypes = [Symbol]
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library.LLVMGetSymbolName.restype = c_char_p
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library.LLVMGetSymbolAddress.argtypes = [Symbol]
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library.LLVMGetSymbolAddress.restype = c_uint64
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library.LLVMGetSymbolFileOffset.argtypes = [Symbol]
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library.LLVMGetSymbolFileOffset.restype = c_uint64
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library.LLVMGetSymbolSize.argtypes = [Symbol]
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library.LLVMGetSymbolSize.restype = c_uint64
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library.LLVMGetRelocationAddress.argtypes = [c_object_p]
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library.LLVMGetRelocationAddress.restype = c_uint64
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library.LLVMGetRelocationOffset.argtypes = [c_object_p]
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library.LLVMGetRelocationOffset.restype = c_uint64
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library.LLVMGetRelocationSymbol.argtypes = [c_object_p]
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library.LLVMGetRelocationSymbol.restype = c_object_p
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library.LLVMGetRelocationType.argtypes = [c_object_p]
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library.LLVMGetRelocationType.restype = c_uint64
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library.LLVMGetRelocationTypeName.argtypes = [c_object_p]
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library.LLVMGetRelocationTypeName.restype = c_char_p
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library.LLVMGetRelocationValueString.argtypes = [c_object_p]
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library.LLVMGetRelocationValueString.restype = c_char_p
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lib = get_library()
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register_library(lib)
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