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497 lines
20 KiB
497 lines
20 KiB
#!/usr/bin/env python
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"""A tool for extracting a list of symbols to export
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When exporting symbols from a dll or exe we either need to mark the symbols in
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the source code as __declspec(dllexport) or supply a list of symbols to the
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linker. This program automates the latter by inspecting the symbol tables of a
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list of link inputs and deciding which of those symbols need to be exported.
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We can't just export all the defined symbols, as there's a limit of 65535
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exported symbols and in clang we go way over that, particularly in a debug
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build. Therefore a large part of the work is pruning symbols either which can't
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be imported, or which we think are things that have definitions in public header
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files (i.e. template instantiations) and we would get defined in the thing
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importing these symbols anyway.
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"""
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from __future__ import print_function
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import sys
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import re
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import os
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import subprocess
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import multiprocessing
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import argparse
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# Define functions which extract a list of symbols from a library using several
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# different tools. We use subprocess.Popen and yield a symbol at a time instead
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# of using subprocess.check_output and returning a list as, especially on
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# Windows, waiting for the entire output to be ready can take a significant
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# amount of time.
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def dumpbin_get_symbols(lib):
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process = subprocess.Popen(['dumpbin','/symbols',lib], bufsize=1,
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stdout=subprocess.PIPE, stdin=subprocess.PIPE,
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universal_newlines=True)
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process.stdin.close()
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for line in process.stdout:
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# Look for external symbols that are defined in some section
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match = re.match("^.+SECT.+External\s+\|\s+(\S+).*$", line)
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if match:
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yield match.group(1)
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process.wait()
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def nm_get_symbols(lib):
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process = subprocess.Popen(['nm',lib], bufsize=1,
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stdout=subprocess.PIPE, stdin=subprocess.PIPE,
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universal_newlines=True)
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process.stdin.close()
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for line in process.stdout:
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# Look for external symbols that are defined in some section
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match = re.match("^\S+\s+[BDGRSTVW]\s+(\S+)$", line)
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if match:
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yield match.group(1)
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process.wait()
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def readobj_get_symbols(lib):
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process = subprocess.Popen(['llvm-readobj','-symbols',lib], bufsize=1,
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stdout=subprocess.PIPE, stdin=subprocess.PIPE,
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universal_newlines=True)
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process.stdin.close()
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for line in process.stdout:
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# When looking through the output of llvm-readobj we expect to see Name,
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# Section, then StorageClass, so record Name and Section when we see
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# them and decide if this is a defined external symbol when we see
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# StorageClass.
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match = re.search('Name: (\S+)', line)
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if match:
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name = match.group(1)
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match = re.search('Section: (\S+)', line)
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if match:
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section = match.group(1)
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match = re.search('StorageClass: (\S+)', line)
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if match:
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storageclass = match.group(1)
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if section != 'IMAGE_SYM_ABSOLUTE' and \
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section != 'IMAGE_SYM_UNDEFINED' and \
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storageclass == 'External':
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yield name
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process.wait()
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# Define functions which determine if the target is 32-bit Windows (as that's
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# where calling convention name decoration happens).
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def dumpbin_is_32bit_windows(lib):
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# dumpbin /headers can output a huge amount of data (>100MB in a debug
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# build) so we read only up to the 'machine' line then close the output.
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process = subprocess.Popen(['dumpbin','/headers',lib], bufsize=1,
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stdout=subprocess.PIPE, stdin=subprocess.PIPE,
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universal_newlines=True)
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process.stdin.close()
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retval = False
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for line in process.stdout:
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match = re.match('.+machine \((\S+)\)', line)
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if match:
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retval = (match.group(1) == 'x86')
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break
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process.stdout.close()
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process.wait()
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return retval
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def objdump_is_32bit_windows(lib):
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output = subprocess.check_output(['objdump','-f',lib],
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universal_newlines=True)
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for line in output:
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match = re.match('.+file format (\S+)', line)
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if match:
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return (match.group(1) == 'pe-i386')
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return False
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def readobj_is_32bit_windows(lib):
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output = subprocess.check_output(['llvm-readobj','-file-headers',lib],
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universal_newlines=True)
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for line in output:
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match = re.match('Format: (\S+)', line)
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if match:
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return (match.group(1) == 'COFF-i386')
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return False
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# MSVC mangles names to ?<identifier_mangling>@<type_mangling>. By examining the
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# identifier/type mangling we can decide which symbols could possibly be
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# required and which we can discard.
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def should_keep_microsoft_symbol(symbol, calling_convention_decoration):
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# Keep unmangled (i.e. extern "C") names
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if not '?' in symbol:
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if calling_convention_decoration:
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# Remove calling convention decoration from names
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match = re.match('[_@]([^@]+)', symbol)
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if match:
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return match.group(1)
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return symbol
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# Function template instantiations start with ?$, discard them as it's
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# assumed that the definition is public
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elif symbol.startswith('??$'):
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return None
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# Deleting destructors start with ?_G or ?_E and can be discarded because
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# link.exe gives you a warning telling you they can't be exported if you
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# don't
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elif symbol.startswith('??_G') or symbol.startswith('??_E'):
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return None
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# Constructors (?0) and destructors (?1) of templates (?$) are assumed to be
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# defined in headers and not required to be kept
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elif symbol.startswith('??0?$') or symbol.startswith('??1?$'):
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return None
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# An anonymous namespace is mangled as ?A(maybe hex number)@. Any symbol
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# that mentions an anonymous namespace can be discarded, as the anonymous
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# namespace doesn't exist outside of that translation unit.
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elif re.search('\?A(0x\w+)?@', symbol):
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return None
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# Keep mangled llvm:: and clang:: function symbols. How we detect these is a
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# bit of a mess and imprecise, but that avoids having to completely demangle
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# the symbol name. The outermost namespace is at the end of the identifier
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# mangling, and the identifier mangling is followed by the type mangling, so
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# we look for (llvm|clang)@@ followed by something that looks like a
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# function type mangling. To spot a function type we use (this is derived
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# from clang/lib/AST/MicrosoftMangle.cpp):
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# <function-type> ::= <function-class> <this-cvr-qualifiers>
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# <calling-convention> <return-type>
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# <argument-list> <throw-spec>
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# <function-class> ::= [A-Z]
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# <this-cvr-qualifiers> ::= [A-Z0-9_]*
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# <calling-convention> ::= [A-JQ]
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# <return-type> ::= .+
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# <argument-list> ::= X (void)
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# ::= .+@ (list of types)
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# ::= .*Z (list of types, varargs)
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# <throw-spec> ::= exceptions are not allowed
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elif re.search('(llvm|clang)@@[A-Z][A-Z0-9_]*[A-JQ].+(X|.+@|.*Z)$', symbol):
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return symbol
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return None
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# Itanium manglings are of the form _Z<identifier_mangling><type_mangling>. We
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# demangle the identifier mangling to identify symbols that can be safely
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# discarded.
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def should_keep_itanium_symbol(symbol, calling_convention_decoration):
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# Start by removing any calling convention decoration (which we expect to
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# see on all symbols, even mangled C++ symbols)
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if calling_convention_decoration and symbol.startswith('_'):
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symbol = symbol[1:]
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# Keep unmangled names
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if not symbol.startswith('_') and not symbol.startswith('.'):
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return symbol
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# Discard manglings that aren't nested names
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match = re.match('_Z(T[VTIS])?(N.+)', symbol)
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if not match:
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return None
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# Demangle the name. If the name is too complex then we don't need to keep
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# it, but it the demangling fails then keep the symbol just in case.
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try:
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names, _ = parse_itanium_nested_name(match.group(2))
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except TooComplexName:
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return None
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if not names:
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return symbol
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# Constructors and destructors of templates classes are assumed to be
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# defined in headers and not required to be kept
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if re.match('[CD][123]', names[-1][0]) and names[-2][1]:
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return None
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# Discard function template instantiations as it's assumed that the
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# definition is public
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elif names[-1][1]:
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return None
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# Keep llvm:: and clang:: names
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elif names[0][0] == '4llvm' or names[0][0] == '5clang':
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return symbol
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# Discard everything else
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else:
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return None
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# Certain kinds of complex manglings we assume cannot be part of a public
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# interface, and we handle them by raising an exception.
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class TooComplexName(Exception):
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pass
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# Parse an itanium mangled name from the start of a string and return a
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# (name, rest of string) pair.
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def parse_itanium_name(arg):
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# Check for a normal name
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match = re.match('(\d+)(.+)', arg)
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if match:
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n = int(match.group(1))
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name = match.group(1)+match.group(2)[:n]
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rest = match.group(2)[n:]
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return name, rest
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# Check for constructor/destructor names
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match = re.match('([CD][123])(.+)', arg)
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if match:
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return match.group(1), match.group(2)
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# Assume that a sequence of characters that doesn't end a nesting is an
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# operator (this is very imprecise, but appears to be good enough)
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match = re.match('([^E]+)(.+)', arg)
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if match:
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return match.group(1), match.group(2)
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# Anything else: we can't handle it
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return None, arg
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# Parse an itanium mangled template argument list from the start of a string
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# and throw it away, returning the rest of the string.
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def skip_itanium_template(arg):
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# A template argument list starts with I
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assert arg.startswith('I'), arg
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tmp = arg[1:]
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while tmp:
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# Check for names
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match = re.match('(\d+)(.+)', tmp)
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if match:
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n = int(match.group(1))
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tmp = match.group(2)[n:]
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continue
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# Check for substitutions
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match = re.match('S[A-Z0-9]*_(.+)', tmp)
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if match:
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tmp = match.group(1)
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# Start of a template
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elif tmp.startswith('I'):
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tmp = skip_itanium_template(tmp)
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# Start of a nested name
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elif tmp.startswith('N'):
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_, tmp = parse_itanium_nested_name(tmp)
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# Start of an expression: assume that it's too complicated
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elif tmp.startswith('L') or tmp.startswith('X'):
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raise TooComplexName
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# End of the template
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elif tmp.startswith('E'):
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return tmp[1:]
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# Something else: probably a type, skip it
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else:
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tmp = tmp[1:]
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return None
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# Parse an itanium mangled nested name and transform it into a list of pairs of
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# (name, is_template), returning (list, rest of string).
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def parse_itanium_nested_name(arg):
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# A nested name starts with N
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assert arg.startswith('N'), arg
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ret = []
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# Skip past the N, and possibly a substitution
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match = re.match('NS[A-Z0-9]*_(.+)', arg)
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if match:
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tmp = match.group(1)
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else:
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tmp = arg[1:]
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# Skip past CV-qualifiers and ref qualifiers
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match = re.match('[rVKRO]*(.+)', tmp);
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if match:
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tmp = match.group(1)
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# Repeatedly parse names from the string until we reach the end of the
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# nested name
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while tmp:
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# An E ends the nested name
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if tmp.startswith('E'):
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return ret, tmp[1:]
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# Parse a name
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name_part, tmp = parse_itanium_name(tmp)
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if not name_part:
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# If we failed then we don't know how to demangle this
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return None, None
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is_template = False
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# If this name is a template record that, then skip the template
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# arguments
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if tmp.startswith('I'):
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tmp = skip_itanium_template(tmp)
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is_template = True
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# Add the name to the list
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ret.append((name_part, is_template))
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# If we get here then something went wrong
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return None, None
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def extract_symbols(arg):
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get_symbols, should_keep_symbol, calling_convention_decoration, lib = arg
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symbols = dict()
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for symbol in get_symbols(lib):
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symbol = should_keep_symbol(symbol, calling_convention_decoration)
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if symbol:
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symbols[symbol] = 1 + symbols.setdefault(symbol,0)
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return symbols
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if __name__ == '__main__':
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tool_exes = ['dumpbin','nm','objdump','llvm-readobj']
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parser = argparse.ArgumentParser(
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description='Extract symbols to export from libraries')
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parser.add_argument('--mangling', choices=['itanium','microsoft'],
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required=True, help='expected symbol mangling scheme')
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parser.add_argument('--tools', choices=tool_exes, nargs='*',
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help='tools to use to extract symbols and determine the'
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' target')
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parser.add_argument('libs', metavar='lib', type=str, nargs='+',
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help='libraries to extract symbols from')
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parser.add_argument('-o', metavar='file', type=str, help='output to file')
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args = parser.parse_args()
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# Determine the function to use to get the list of symbols from the inputs,
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# and the function to use to determine if the target is 32-bit windows.
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tools = { 'dumpbin' : (dumpbin_get_symbols, dumpbin_is_32bit_windows),
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'nm' : (nm_get_symbols, None),
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'objdump' : (None, objdump_is_32bit_windows),
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'llvm-readobj' : (readobj_get_symbols, readobj_is_32bit_windows) }
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get_symbols = None
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is_32bit_windows = None
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# If we have a tools argument then use that for the list of tools to check
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if args.tools:
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tool_exes = args.tools
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# Find a tool to use by trying each in turn until we find one that exists
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# (subprocess.call will throw OSError when the program does not exist)
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get_symbols = None
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for exe in tool_exes:
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try:
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# Close std streams as we don't want any output and we don't
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# want the process to wait for something on stdin.
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p = subprocess.Popen([exe], stdout=subprocess.PIPE,
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stderr=subprocess.PIPE,
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stdin=subprocess.PIPE,
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universal_newlines=True)
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p.stdout.close()
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p.stderr.close()
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p.stdin.close()
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p.wait()
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# Keep going until we have a tool to use for both get_symbols and
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# is_32bit_windows
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if not get_symbols:
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get_symbols = tools[exe][0]
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if not is_32bit_windows:
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is_32bit_windows = tools[exe][1]
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if get_symbols and is_32bit_windows:
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break
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except OSError:
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continue
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if not get_symbols:
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print("Couldn't find a program to read symbols with", file=sys.stderr)
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exit(1)
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if not is_32bit_windows:
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print("Couldn't find a program to determing the target", file=sys.stderr)
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exit(1)
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# How we determine which symbols to keep and which to discard depends on
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# the mangling scheme
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if args.mangling == 'microsoft':
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should_keep_symbol = should_keep_microsoft_symbol
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else:
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should_keep_symbol = should_keep_itanium_symbol
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# Get the list of libraries to extract symbols from
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libs = list()
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for lib in args.libs:
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# When invoked by cmake the arguments are the cmake target names of the
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# libraries, so we need to add .lib/.a to the end and maybe lib to the
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# start to get the filename. Also allow objects.
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suffixes = ['.lib','.a','.obj','.o']
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if not any([lib.endswith(s) for s in suffixes]):
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for s in suffixes:
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if os.path.exists(lib+s):
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lib = lib+s
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break
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if os.path.exists('lib'+lib+s):
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lib = 'lib'+lib+s
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break
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if not any([lib.endswith(s) for s in suffixes]):
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print("Don't know what to do with argument "+lib, file=sys.stderr)
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exit(1)
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libs.append(lib)
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# Check if calling convention decoration is used by inspecting the first
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# library in the list
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calling_convention_decoration = is_32bit_windows(libs[0])
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# Extract symbols from libraries in parallel. This is a huge time saver when
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# doing a debug build, as there are hundreds of thousands of symbols in each
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# library.
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pool = multiprocessing.Pool()
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try:
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# Only one argument can be passed to the mapping function, and we can't
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# use a lambda or local function definition as that doesn't work on
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# windows, so create a list of tuples which duplicates the arguments
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# that are the same in all calls.
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vals = [(get_symbols, should_keep_symbol, calling_convention_decoration, x) for x in libs]
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# Do an async map then wait for the result to make sure that
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# KeyboardInterrupt gets caught correctly (see
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# http://bugs.python.org/issue8296)
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result = pool.map_async(extract_symbols, vals)
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pool.close()
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libs_symbols = result.get(3600)
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except KeyboardInterrupt:
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# On Ctrl-C terminate everything and exit
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pool.terminate()
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pool.join()
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exit(1)
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# Merge everything into a single dict
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symbols = dict()
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for this_lib_symbols in libs_symbols:
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for k,v in list(this_lib_symbols.items()):
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symbols[k] = v + symbols.setdefault(k,0)
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# Count instances of member functions of template classes, and map the
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# symbol name to the function+class. We do this under the assumption that if
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# a member function of a template class is instantiated many times it's
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# probably declared in a public header file.
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template_function_count = dict()
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template_function_mapping = dict()
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template_function_count[""] = 0
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for k in symbols:
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name = None
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if args.mangling == 'microsoft':
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# Member functions of templates start with
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# ?<fn_name>@?$<class_name>@, so we map to <fn_name>@?$<class_name>.
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# As manglings go from the innermost scope to the outermost scope
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# this means:
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# * When we have a function member of a subclass of a template
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# class then <fn_name> will actually contain the mangling of
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# both the subclass and the function member. This is fine.
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# * When we have a function member of a template subclass of a
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# (possibly template) class then it's the innermost template
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# subclass that becomes <class_name>. This should be OK so long
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# as we don't have multiple classes with a template subclass of
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# the same name.
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match = re.search("^\?(\??\w+\@\?\$\w+)\@", k)
|
|
if match:
|
|
name = match.group(1)
|
|
else:
|
|
# Find member functions of templates by demangling the name and
|
|
# checking if the second-to-last name in the list is a template.
|
|
match = re.match('_Z(T[VTIS])?(N.+)', k)
|
|
if match:
|
|
try:
|
|
names, _ = parse_itanium_nested_name(match.group(2))
|
|
if names and names[-2][1]:
|
|
name = ''.join([x for x,_ in names])
|
|
except TooComplexName:
|
|
# Manglings that are too complex should already have been
|
|
# filtered out, but if we happen to somehow see one here
|
|
# just leave it as-is.
|
|
pass
|
|
if name:
|
|
old_count = template_function_count.setdefault(name,0)
|
|
template_function_count[name] = old_count + 1
|
|
template_function_mapping[k] = name
|
|
else:
|
|
template_function_mapping[k] = ""
|
|
|
|
# Print symbols which both:
|
|
# * Appear in exactly one input, as symbols defined in multiple
|
|
# objects/libraries are assumed to have public definitions.
|
|
# * Aren't instances of member functions of templates which have been
|
|
# instantiated 100 times or more, which are assumed to have public
|
|
# definitions. (100 is an arbitrary guess here.)
|
|
if args.o:
|
|
outfile = open(args.o,'w')
|
|
else:
|
|
outfile = sys.stdout
|
|
for k,v in list(symbols.items()):
|
|
template_count = template_function_count[template_function_mapping[k]]
|
|
if v == 1 and template_count < 100:
|
|
print(k, file=outfile)
|