221 lines
7.2 KiB
Python
221 lines
7.2 KiB
Python
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# This implements the "diagnose-nsstring" command, usually installed in the debug session like
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# command script import lldb.diagnose
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# it is used when NSString summary formatter fails to replicate the logic that went into LLDB making the
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# decisions it did and providing some useful context information that can
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# be used for improving the formatter
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import lldb
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def read_memory(process, location, size):
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data = ""
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error = lldb.SBError()
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for x in range(0, size - 1):
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byte = process.ReadUnsignedFromMemory(x + location, 1, error)
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if error.fail:
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data = data + "err%s" % "" if x == size - 2 else ":"
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else:
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try:
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data = data + "0x%x" % byte
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if byte == 0:
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data = data + "(\\0)"
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elif byte == 0xA:
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data = data + "(\\a)"
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elif byte == 0xB:
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data = data + "(\\b)"
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elif byte == 0xC:
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data = data + "(\\c)"
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elif byte == "\n":
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data = data + "(\\n)"
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else:
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data = data + "(%s)" % chr(byte)
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if x < size - 2:
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data = data + ":"
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except Exception as e:
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print(e)
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return data
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def diagnose_nsstring_Command_Impl(debugger, command, result, internal_dict):
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"""
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A command to diagnose the LLDB NSString data formatter
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invoke as
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(lldb) diagnose-nsstring <expr returning NSString>
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e.g.
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(lldb) diagnose-nsstring @"Hello world"
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"""
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target = debugger.GetSelectedTarget()
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process = target.GetProcess()
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thread = process.GetSelectedThread()
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frame = thread.GetSelectedFrame()
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if not target.IsValid() or not process.IsValid():
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return "unable to get target/process - cannot proceed"
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options = lldb.SBExpressionOptions()
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options.SetFetchDynamicValue()
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error = lldb.SBError()
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if frame.IsValid():
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nsstring = frame.EvaluateExpression(command, options)
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else:
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nsstring = target.EvaluateExpression(command, options)
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print(str(nsstring), file=result)
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nsstring_address = nsstring.GetValueAsUnsigned(0)
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if nsstring_address == 0:
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return "unable to obtain the string - cannot proceed"
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expression = "\
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struct $__lldb__notInlineMutable {\
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char* buffer;\
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signed long length;\
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signed long capacity;\
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unsigned int hasGap:1;\
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unsigned int isFixedCapacity:1;\
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unsigned int isExternalMutable:1;\
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unsigned int capacityProvidedExternally:1;\n\
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#if __LP64__\n\
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unsigned long desiredCapacity:60;\n\
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#else\n\
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unsigned long desiredCapacity:28;\n\
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#endif\n\
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void* contentsAllocator;\
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};\
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\
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struct $__lldb__CFString {\
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void* _cfisa;\
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uint8_t _cfinfo[4];\
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uint32_t _rc;\
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union {\
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struct __inline1 {\
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signed long length;\
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} inline1;\
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struct __notInlineImmutable1 {\
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char* buffer;\
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signed long length;\
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void* contentsDeallocator;\
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} notInlineImmutable1;\
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struct __notInlineImmutable2 {\
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char* buffer;\
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void* contentsDeallocator;\
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} notInlineImmutable2;\
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struct $__lldb__notInlineMutable notInlineMutable;\
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} variants;\
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};\
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"
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expression = expression + "*(($__lldb__CFString*) %d)" % nsstring_address
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# print expression
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dumped = target.EvaluateExpression(expression, options)
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print(str(dumped), file=result)
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little_endian = target.byte_order == lldb.eByteOrderLittle
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ptr_size = target.addr_size
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info_bits = (
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dumped.GetChildMemberWithName("_cfinfo")
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.GetChildAtIndex(0 if little_endian else 3)
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.GetValueAsUnsigned(0)
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)
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is_mutable = (info_bits & 1) == 1
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is_inline = (info_bits & 0x60) == 0
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has_explicit_length = (info_bits & (1 | 4)) != 4
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is_unicode = (info_bits & 0x10) == 0x10
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is_special = (
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nsstring.GetDynamicValue(lldb.eDynamicCanRunTarget).GetTypeName()
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== "NSPathStore2"
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)
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has_null = (info_bits & 8) == 8
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print(
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"\nInfo=%d\nMutable=%s\nInline=%s\nExplicit=%s\nUnicode=%s\nSpecial=%s\nNull=%s\n"
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% (
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info_bits,
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"yes" if is_mutable else "no",
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"yes" if is_inline else "no",
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"yes" if has_explicit_length else "no",
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"yes" if is_unicode else "no",
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"yes" if is_special else "no",
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"yes" if has_null else "no",
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),
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file=result,
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)
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explicit_length_offset = 0
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if not has_null and has_explicit_length and not is_special:
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explicit_length_offset = 2 * ptr_size
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if is_mutable and not is_inline:
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explicit_length_offset = explicit_length_offset + ptr_size
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elif is_inline:
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pass
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elif not is_inline and not is_mutable:
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explicit_length_offset = explicit_length_offset + ptr_size
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else:
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explicit_length_offset = 0
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if explicit_length_offset == 0:
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print("There is no explicit length marker - skipping this step\n", file=result)
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else:
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explicit_length_offset = nsstring_address + explicit_length_offset
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explicit_length = process.ReadUnsignedFromMemory(
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explicit_length_offset, 4, error
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)
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print(
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"Explicit length location is at 0x%x - read value is %d\n"
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% (explicit_length_offset, explicit_length),
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file=result,
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)
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if is_mutable:
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location = 2 * ptr_size + nsstring_address
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location = process.ReadPointerFromMemory(location, error)
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elif (
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is_inline
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and has_explicit_length
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and not is_unicode
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and not is_special
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and not is_mutable
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):
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location = 3 * ptr_size + nsstring_address
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elif is_unicode:
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location = 2 * ptr_size + nsstring_address
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if is_inline:
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if not has_explicit_length:
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print(
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"Unicode & Inline & !Explicit is a new combo - no formula for it",
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file=result,
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)
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else:
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location += ptr_size
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else:
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location = process.ReadPointerFromMemory(location, error)
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elif is_special:
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location = nsstring_address + ptr_size + 4
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elif is_inline:
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location = 2 * ptr_size + nsstring_address
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if not has_explicit_length:
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location += 1
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else:
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location = 2 * ptr_size + nsstring_address
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location = process.ReadPointerFromMemory(location, error)
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print("Expected data location: 0x%x\n" % (location), file=result)
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print(
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"1K of data around location: %s\n" % read_memory(process, location, 1024),
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file=result,
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)
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print(
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"5K of data around string pointer: %s\n"
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% read_memory(process, nsstring_address, 1024 * 5),
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file=result,
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)
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def __lldb_init_module(debugger, internal_dict):
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debugger.HandleCommand(
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"command script add -o -f %s.diagnose_nsstring_Command_Impl diagnose-nsstring"
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% __name__
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)
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print(
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'The "diagnose-nsstring" command has been installed, type "help diagnose-nsstring" for detailed help.'
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)
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__lldb_init_module(lldb.debugger, None)
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__lldb_init_module = None
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