| #!/usr/bin/env python |
| |
| """A tool for extracting a list of symbols to export |
| |
| When exporting symbols from a dll or exe we either need to mark the symbols in |
| the source code as __declspec(dllexport) or supply a list of symbols to the |
| linker. This program automates the latter by inspecting the symbol tables of a |
| list of link inputs and deciding which of those symbols need to be exported. |
| |
| We can't just export all the defined symbols, as there's a limit of 65535 |
| exported symbols and in clang we go way over that, particularly in a debug |
| build. Therefore a large part of the work is pruning symbols either which can't |
| be imported, or which we think are things that have definitions in public header |
| files (i.e. template instantiations) and we would get defined in the thing |
| importing these symbols anyway. |
| """ |
| |
| from __future__ import print_function |
| import sys |
| import re |
| import os |
| import subprocess |
| import multiprocessing |
| import argparse |
| |
| # Define functions which extract a list of symbols from a library using several |
| # different tools. We use subprocess.Popen and yield a symbol at a time instead |
| # of using subprocess.check_output and returning a list as, especially on |
| # Windows, waiting for the entire output to be ready can take a significant |
| # amount of time. |
| |
| def dumpbin_get_symbols(lib): |
| process = subprocess.Popen(['dumpbin','/symbols',lib], bufsize=1, |
| stdout=subprocess.PIPE, stdin=subprocess.PIPE, |
| universal_newlines=True) |
| process.stdin.close() |
| for line in process.stdout: |
| # Look for external symbols that are defined in some section |
| match = re.match("^.+SECT.+External\s+\|\s+(\S+).*$", line) |
| if match: |
| yield match.group(1) |
| process.wait() |
| |
| def nm_get_symbols(lib): |
| process = subprocess.Popen(['nm',lib], bufsize=1, |
| stdout=subprocess.PIPE, stdin=subprocess.PIPE, |
| universal_newlines=True) |
| process.stdin.close() |
| for line in process.stdout: |
| # Look for external symbols that are defined in some section |
| match = re.match("^\S+\s+[BDGRSTVW]\s+(\S+)$", line) |
| if match: |
| yield match.group(1) |
| process.wait() |
| |
| def readobj_get_symbols(lib): |
| process = subprocess.Popen(['llvm-readobj','-symbols',lib], bufsize=1, |
| stdout=subprocess.PIPE, stdin=subprocess.PIPE, |
| universal_newlines=True) |
| process.stdin.close() |
| for line in process.stdout: |
| # When looking through the output of llvm-readobj we expect to see Name, |
| # Section, then StorageClass, so record Name and Section when we see |
| # them and decide if this is a defined external symbol when we see |
| # StorageClass. |
| match = re.search('Name: (\S+)', line) |
| if match: |
| name = match.group(1) |
| match = re.search('Section: (\S+)', line) |
| if match: |
| section = match.group(1) |
| match = re.search('StorageClass: (\S+)', line) |
| if match: |
| storageclass = match.group(1) |
| if section != 'IMAGE_SYM_ABSOLUTE' and \ |
| section != 'IMAGE_SYM_UNDEFINED' and \ |
| storageclass == 'External': |
| yield name |
| process.wait() |
| |
| # Define functions which determine if the target is 32-bit Windows (as that's |
| # where calling convention name decoration happens). |
| |
| def dumpbin_is_32bit_windows(lib): |
| # dumpbin /headers can output a huge amount of data (>100MB in a debug |
| # build) so we read only up to the 'machine' line then close the output. |
| process = subprocess.Popen(['dumpbin','/headers',lib], bufsize=1, |
| stdout=subprocess.PIPE, stdin=subprocess.PIPE, |
| universal_newlines=True) |
| process.stdin.close() |
| retval = False |
| for line in process.stdout: |
| match = re.match('.+machine \((\S+)\)', line) |
| if match: |
| retval = (match.group(1) == 'x86') |
| break |
| process.stdout.close() |
| process.wait() |
| return retval |
| |
| def objdump_is_32bit_windows(lib): |
| output = subprocess.check_output(['objdump','-f',lib], |
| universal_newlines=True) |
| for line in output: |
| match = re.match('.+file format (\S+)', line) |
| if match: |
| return (match.group(1) == 'pe-i386') |
| return False |
| |
| def readobj_is_32bit_windows(lib): |
| output = subprocess.check_output(['llvm-readobj','-file-headers',lib], |
| universal_newlines=True) |
| for line in output: |
| match = re.match('Format: (\S+)', line) |
| if match: |
| return (match.group(1) == 'COFF-i386') |
| return False |
| |
| # MSVC mangles names to ?<identifier_mangling>@<type_mangling>. By examining the |
| # identifier/type mangling we can decide which symbols could possibly be |
| # required and which we can discard. |
| def should_keep_microsoft_symbol(symbol, calling_convention_decoration): |
| # Keep unmangled (i.e. extern "C") names |
| if not '?' in symbol: |
| if calling_convention_decoration: |
| # Remove calling convention decoration from names |
| match = re.match('[_@]([^@]+)', symbol) |
| if match: |
| return match.group(1) |
| return symbol |
| # Function template instantiations start with ?$; keep the instantiations of |
| # clang::Type::getAs, as some of them are explipict specializations that are |
| # defined in clang's lib/AST/Type.cpp; discard the rest as it's assumed that |
| # the definition is public |
| elif re.match('\?\?\$getAs@.+@Type@clang@@', symbol): |
| return symbol |
| elif symbol.startswith('??$'): |
| return None |
| # Deleting destructors start with ?_G or ?_E and can be discarded because |
| # link.exe gives you a warning telling you they can't be exported if you |
| # don't |
| elif symbol.startswith('??_G') or symbol.startswith('??_E'): |
| return None |
| # Constructors (?0) and destructors (?1) of templates (?$) are assumed to be |
| # defined in headers and not required to be kept |
| elif symbol.startswith('??0?$') or symbol.startswith('??1?$'): |
| return None |
| # An anonymous namespace is mangled as ?A(maybe hex number)@. Any symbol |
| # that mentions an anonymous namespace can be discarded, as the anonymous |
| # namespace doesn't exist outside of that translation unit. |
| elif re.search('\?A(0x\w+)?@', symbol): |
| return None |
| # Keep mangled llvm:: and clang:: function symbols. How we detect these is a |
| # bit of a mess and imprecise, but that avoids having to completely demangle |
| # the symbol name. The outermost namespace is at the end of the identifier |
| # mangling, and the identifier mangling is followed by the type mangling, so |
| # we look for (llvm|clang)@@ followed by something that looks like a |
| # function type mangling. To spot a function type we use (this is derived |
| # from clang/lib/AST/MicrosoftMangle.cpp): |
| # <function-type> ::= <function-class> <this-cvr-qualifiers> |
| # <calling-convention> <return-type> |
| # <argument-list> <throw-spec> |
| # <function-class> ::= [A-Z] |
| # <this-cvr-qualifiers> ::= [A-Z0-9_]* |
| # <calling-convention> ::= [A-JQ] |
| # <return-type> ::= .+ |
| # <argument-list> ::= X (void) |
| # ::= .+@ (list of types) |
| # ::= .*Z (list of types, varargs) |
| # <throw-spec> ::= exceptions are not allowed |
| elif re.search('(llvm|clang)@@[A-Z][A-Z0-9_]*[A-JQ].+(X|.+@|.*Z)$', symbol): |
| return symbol |
| return None |
| |
| # Itanium manglings are of the form _Z<identifier_mangling><type_mangling>. We |
| # demangle the identifier mangling to identify symbols that can be safely |
| # discarded. |
| def should_keep_itanium_symbol(symbol, calling_convention_decoration): |
| # Start by removing any calling convention decoration (which we expect to |
| # see on all symbols, even mangled C++ symbols) |
| if calling_convention_decoration and symbol.startswith('_'): |
| symbol = symbol[1:] |
| # Keep unmangled names |
| if not symbol.startswith('_') and not symbol.startswith('.'): |
| return symbol |
| # Discard manglings that aren't nested names |
| match = re.match('_Z(T[VTIS])?(N.+)', symbol) |
| if not match: |
| return None |
| # Demangle the name. If the name is too complex then we don't need to keep |
| # it, but it the demangling fails then keep the symbol just in case. |
| try: |
| names, _ = parse_itanium_nested_name(match.group(2)) |
| except TooComplexName: |
| return None |
| if not names: |
| return symbol |
| # Constructors and destructors of templates classes are assumed to be |
| # defined in headers and not required to be kept |
| if re.match('[CD][123]', names[-1][0]) and names[-2][1]: |
| return None |
| # Keep the instantiations of clang::Type::getAs, as some of them are |
| # explipict specializations that are defined in clang's lib/AST/Type.cpp; |
| # discard any other function template instantiations as it's assumed that |
| # the definition is public |
| elif symbol.startswith('_ZNK5clang4Type5getAs'): |
| return symbol |
| elif names[-1][1]: |
| return None |
| # Keep llvm:: and clang:: names |
| elif names[0][0] == '4llvm' or names[0][0] == '5clang': |
| return symbol |
| # Discard everything else |
| else: |
| return None |
| |
| # Certain kinds of complex manglings we assume cannot be part of a public |
| # interface, and we handle them by raising an exception. |
| class TooComplexName(Exception): |
| pass |
| |
| # Parse an itanium mangled name from the start of a string and return a |
| # (name, rest of string) pair. |
| def parse_itanium_name(arg): |
| # Check for a normal name |
| match = re.match('(\d+)(.+)', arg) |
| if match: |
| n = int(match.group(1)) |
| name = match.group(1)+match.group(2)[:n] |
| rest = match.group(2)[n:] |
| return name, rest |
| # Check for constructor/destructor names |
| match = re.match('([CD][123])(.+)', arg) |
| if match: |
| return match.group(1), match.group(2) |
| # Assume that a sequence of characters that doesn't end a nesting is an |
| # operator (this is very imprecise, but appears to be good enough) |
| match = re.match('([^E]+)(.+)', arg) |
| if match: |
| return match.group(1), match.group(2) |
| # Anything else: we can't handle it |
| return None, arg |
| |
| # Parse an itanium mangled template argument list from the start of a string |
| # and throw it away, returning the rest of the string. |
| def skip_itanium_template(arg): |
| # A template argument list starts with I |
| assert arg.startswith('I'), arg |
| tmp = arg[1:] |
| while tmp: |
| # Check for names |
| match = re.match('(\d+)(.+)', tmp) |
| if match: |
| n = int(match.group(1)) |
| tmp = match.group(2)[n:] |
| continue |
| # Check for substitutions |
| match = re.match('S[A-Z0-9]*_(.+)', tmp) |
| if match: |
| tmp = match.group(1) |
| # Start of a template |
| elif tmp.startswith('I'): |
| tmp = skip_itanium_template(tmp) |
| # Start of a nested name |
| elif tmp.startswith('N'): |
| _, tmp = parse_itanium_nested_name(tmp) |
| # Start of an expression: assume that it's too complicated |
| elif tmp.startswith('L') or tmp.startswith('X'): |
| raise TooComplexName |
| # End of the template |
| elif tmp.startswith('E'): |
| return tmp[1:] |
| # Something else: probably a type, skip it |
| else: |
| tmp = tmp[1:] |
| return None |
| |
| # Parse an itanium mangled nested name and transform it into a list of pairs of |
| # (name, is_template), returning (list, rest of string). |
| def parse_itanium_nested_name(arg): |
| # A nested name starts with N |
| assert arg.startswith('N'), arg |
| ret = [] |
| |
| # Skip past the N, and possibly a substitution |
| match = re.match('NS[A-Z0-9]*_(.+)', arg) |
| if match: |
| tmp = match.group(1) |
| else: |
| tmp = arg[1:] |
| |
| # Skip past CV-qualifiers and ref qualifiers |
| match = re.match('[rVKRO]*(.+)', tmp); |
| if match: |
| tmp = match.group(1) |
| |
| # Repeatedly parse names from the string until we reach the end of the |
| # nested name |
| while tmp: |
| # An E ends the nested name |
| if tmp.startswith('E'): |
| return ret, tmp[1:] |
| # Parse a name |
| name_part, tmp = parse_itanium_name(tmp) |
| if not name_part: |
| # If we failed then we don't know how to demangle this |
| return None, None |
| is_template = False |
| # If this name is a template record that, then skip the template |
| # arguments |
| if tmp.startswith('I'): |
| tmp = skip_itanium_template(tmp) |
| is_template = True |
| # Add the name to the list |
| ret.append((name_part, is_template)) |
| |
| # If we get here then something went wrong |
| return None, None |
| |
| def extract_symbols(arg): |
| get_symbols, should_keep_symbol, calling_convention_decoration, lib = arg |
| symbols = dict() |
| for symbol in get_symbols(lib): |
| symbol = should_keep_symbol(symbol, calling_convention_decoration) |
| if symbol: |
| symbols[symbol] = 1 + symbols.setdefault(symbol,0) |
| return symbols |
| |
| if __name__ == '__main__': |
| tool_exes = ['dumpbin','nm','objdump','llvm-readobj'] |
| parser = argparse.ArgumentParser( |
| description='Extract symbols to export from libraries') |
| parser.add_argument('--mangling', choices=['itanium','microsoft'], |
| required=True, help='expected symbol mangling scheme') |
| parser.add_argument('--tools', choices=tool_exes, nargs='*', |
| help='tools to use to extract symbols and determine the' |
| ' target') |
| parser.add_argument('libs', metavar='lib', type=str, nargs='+', |
| help='libraries to extract symbols from') |
| parser.add_argument('-o', metavar='file', type=str, help='output to file') |
| args = parser.parse_args() |
| |
| # Determine the function to use to get the list of symbols from the inputs, |
| # and the function to use to determine if the target is 32-bit windows. |
| tools = { 'dumpbin' : (dumpbin_get_symbols, dumpbin_is_32bit_windows), |
| 'nm' : (nm_get_symbols, None), |
| 'objdump' : (None, objdump_is_32bit_windows), |
| 'llvm-readobj' : (readobj_get_symbols, readobj_is_32bit_windows) } |
| get_symbols = None |
| is_32bit_windows = None |
| # If we have a tools argument then use that for the list of tools to check |
| if args.tools: |
| tool_exes = args.tools |
| # Find a tool to use by trying each in turn until we find one that exists |
| # (subprocess.call will throw OSError when the program does not exist) |
| get_symbols = None |
| for exe in tool_exes: |
| try: |
| # Close std streams as we don't want any output and we don't |
| # want the process to wait for something on stdin. |
| p = subprocess.Popen([exe], stdout=subprocess.PIPE, |
| stderr=subprocess.PIPE, |
| stdin=subprocess.PIPE, |
| universal_newlines=True) |
| p.stdout.close() |
| p.stderr.close() |
| p.stdin.close() |
| p.wait() |
| # Keep going until we have a tool to use for both get_symbols and |
| # is_32bit_windows |
| if not get_symbols: |
| get_symbols = tools[exe][0] |
| if not is_32bit_windows: |
| is_32bit_windows = tools[exe][1] |
| if get_symbols and is_32bit_windows: |
| break |
| except OSError: |
| continue |
| if not get_symbols: |
| print("Couldn't find a program to read symbols with", file=sys.stderr) |
| exit(1) |
| if not is_32bit_windows: |
| print("Couldn't find a program to determining the target", file=sys.stderr) |
| exit(1) |
| |
| # How we determine which symbols to keep and which to discard depends on |
| # the mangling scheme |
| if args.mangling == 'microsoft': |
| should_keep_symbol = should_keep_microsoft_symbol |
| else: |
| should_keep_symbol = should_keep_itanium_symbol |
| |
| # Get the list of libraries to extract symbols from |
| libs = list() |
| for lib in args.libs: |
| # When invoked by cmake the arguments are the cmake target names of the |
| # libraries, so we need to add .lib/.a to the end and maybe lib to the |
| # start to get the filename. Also allow objects. |
| suffixes = ['.lib','.a','.obj','.o'] |
| if not any([lib.endswith(s) for s in suffixes]): |
| for s in suffixes: |
| if os.path.exists(lib+s): |
| lib = lib+s |
| break |
| if os.path.exists('lib'+lib+s): |
| lib = 'lib'+lib+s |
| break |
| if not any([lib.endswith(s) for s in suffixes]): |
| print("Don't know what to do with argument "+lib, file=sys.stderr) |
| exit(1) |
| libs.append(lib) |
| |
| # Check if calling convention decoration is used by inspecting the first |
| # library in the list |
| calling_convention_decoration = is_32bit_windows(libs[0]) |
| |
| # Extract symbols from libraries in parallel. This is a huge time saver when |
| # doing a debug build, as there are hundreds of thousands of symbols in each |
| # library. |
| pool = multiprocessing.Pool() |
| try: |
| # Only one argument can be passed to the mapping function, and we can't |
| # use a lambda or local function definition as that doesn't work on |
| # windows, so create a list of tuples which duplicates the arguments |
| # that are the same in all calls. |
| vals = [(get_symbols, should_keep_symbol, calling_convention_decoration, x) for x in libs] |
| # Do an async map then wait for the result to make sure that |
| # KeyboardInterrupt gets caught correctly (see |
| # http://bugs.python.org/issue8296) |
| result = pool.map_async(extract_symbols, vals) |
| pool.close() |
| libs_symbols = result.get(3600) |
| except KeyboardInterrupt: |
| # On Ctrl-C terminate everything and exit |
| pool.terminate() |
| pool.join() |
| exit(1) |
| |
| # Merge everything into a single dict |
| symbols = dict() |
| for this_lib_symbols in libs_symbols: |
| for k,v in list(this_lib_symbols.items()): |
| symbols[k] = v + symbols.setdefault(k,0) |
| |
| # Count instances of member functions of template classes, and map the |
| # symbol name to the function+class. We do this under the assumption that if |
| # a member function of a template class is instantiated many times it's |
| # probably declared in a public header file. |
| template_function_count = dict() |
| template_function_mapping = dict() |
| template_function_count[""] = 0 |
| for k in symbols: |
| name = None |
| if args.mangling == 'microsoft': |
| # Member functions of templates start with |
| # ?<fn_name>@?$<class_name>@, so we map to <fn_name>@?$<class_name>. |
| # As manglings go from the innermost scope to the outermost scope |
| # this means: |
| # * When we have a function member of a subclass of a template |
| # class then <fn_name> will actually contain the mangling of |
| # both the subclass and the function member. This is fine. |
| # * When we have a function member of a template subclass of a |
| # (possibly template) class then it's the innermost template |
| # subclass that becomes <class_name>. This should be OK so long |
| # as we don't have multiple classes with a template subclass of |
| # the same name. |
| 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) |
