How to use do_cleanups method in Slash

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cleanup_check.py

Source:cleanup_check.py

1#   Copyright 2013-2018 Free Software Foundation, Inc.2#3#   This is free software: you can redistribute it and/or modify it4#   under the terms of the GNU General Public License as published by5#   the Free Software Foundation, either version 3 of the License, or6#   (at your option) any later version.7#8#   This program is distributed in the hope that it will be useful, but9#   WITHOUT ANY WARRANTY; without even the implied warranty of10#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU11#   General Public License for more details.12#13#   You should have received a copy of the GNU General Public License14#   along with this program.  If not, see15#   <http://www.gnu.org/licenses/>.16import gcc17import gccutils18import sys19want_raii_info = False20logging = False21show_cfg = False22def log(msg, indent=0):23    global logging24    if logging:25        sys.stderr.write('%s%s\n' % ('  ' * indent, msg))26        sys.stderr.flush()27def is_cleanup_type(return_type):28    if not isinstance(return_type, gcc.PointerType):29        return False30    if not isinstance(return_type.dereference, gcc.RecordType):31        return False32    if str(return_type.dereference.name) == 'cleanup':33        return True34    return False35def is_constructor(decl):36    "Return True if the function DECL is a cleanup constructor; False otherwise"37    return is_cleanup_type(decl.type.type) and (not decl.name or str(decl.name) != 'make_final_cleanup')38destructor_names = set(['do_cleanups', 'discard_cleanups'])39def is_destructor(decl):40    return decl.name in destructor_names41# This list is just much too long... we should probably have an42# attribute instead.43special_names = set(['do_final_cleanups', 'discard_final_cleanups',44                     'save_cleanups', 'save_final_cleanups',45                     'restore_cleanups', 'restore_final_cleanups',46                     'exceptions_state_mc_init',47                     'make_my_cleanup2', 'make_final_cleanup', 'all_cleanups',48                     'save_my_cleanups', 'quit_target'])49def needs_special_treatment(decl):50    return decl.name in special_names51# Sometimes we need a new placeholder object that isn't the same as52# anything else.53class Dummy(object):54    def __init__(self, location):55        self.location = location56# A wrapper for a cleanup which has been assigned to a variable.57# This holds the variable and the location.58class Cleanup(object):59    def __init__(self, var, location):60        self.var = var61        self.location = location62# A class representing a master cleanup.  This holds a stack of63# cleanup objects and supports a merging operation.64class MasterCleanup(object):65    # Create a new MasterCleanup object.  OTHER, if given, is a66    # MasterCleanup object to copy.67    def __init__(self, other = None):68        # 'cleanups' is a list of cleanups.  Each element is either a69        # Dummy, for an anonymous cleanup, or a Cleanup, for a cleanup70        # which was assigned to a variable.71        if other is None:72            self.cleanups = []73            self.aliases = {}74        else:75            self.cleanups = other.cleanups[:]76            self.aliases = dict(other.aliases)77    def compare_vars(self, definition, argument):78        if definition == argument:79            return True80        if argument in self.aliases:81            argument = self.aliases[argument]82        if definition in self.aliases:83            definition = self.aliases[definition]84        return definition == argument85    def note_assignment(self, lhs, rhs):86        log('noting assignment %s = %s' % (lhs, rhs), 4)87        self.aliases[lhs] = rhs88    # Merge with another MasterCleanup.89    # Returns True if this resulted in a change to our state.90    def merge(self, other):91        # We do explicit iteration like this so we can easily92        # update the list after the loop.93        counter = -194        found_named = False95        for counter in range(len(self.cleanups) - 1, -1, -1):96            var = self.cleanups[counter]97            log('merge checking %s' % var, 4)98            # Only interested in named cleanups.99            if isinstance(var, Dummy):100                log('=> merge dummy', 5)101                continue102            # Now see if VAR is found in OTHER.103            if other._find_var(var.var) >= 0:104                log ('=> merge found', 5)105                break106            log('=>merge not found', 5)107            found_named = True108        if found_named and counter < len(self.cleanups) - 1:109            log ('merging to %d' % counter, 4)110            if counter < 0:111                self.cleanups = []112            else:113                self.cleanups = self.cleanups[0:counter]114            return True115        # If SELF is empty but OTHER has some cleanups, then consider116        # that a change as well.117        if len(self.cleanups) == 0 and len(other.cleanups) > 0:118            log('merging non-empty other', 4)119            self.cleanups = other.cleanups[:]120            return True121        return False122    # Push a new constructor onto our stack.  LHS is the123    # left-hand-side of the GimpleCall statement.  It may be None,124    # meaning that this constructor's value wasn't used.125    def push(self, location, lhs):126        if lhs is None:127            obj = Dummy(location)128        else:129            obj = Cleanup(lhs, location)130        log('pushing %s' % lhs, 4)131        idx = self._find_var(lhs)132        if idx >= 0:133            gcc.permerror(location, 'reassigning to known cleanup')134            gcc.inform(self.cleanups[idx].location,135                       'previous assignment is here')136        self.cleanups.append(obj)137    # A helper for merge and pop that finds BACK_TO in self.cleanups,138    # and returns the index, or -1 if not found.139    def _find_var(self, back_to):140        for i in range(len(self.cleanups) - 1, -1, -1):141            if isinstance(self.cleanups[i], Dummy):142                continue143            if self.compare_vars(self.cleanups[i].var, back_to):144                return i145        return -1146    # Pop constructors until we find one matching BACK_TO.147    # This is invoked when we see a do_cleanups call.148    def pop(self, location, back_to):149        log('pop:', 4)150        i = self._find_var(back_to)151        if i >= 0:152            self.cleanups = self.cleanups[0:i]153        else:154            gcc.permerror(location, 'destructor call with unknown argument')155    # Check whether ARG is the current master cleanup.  Return True if156    # all is well.157    def verify(self, location, arg):158        log('verify %s' % arg, 4)159        return (len(self.cleanups) > 0160                and not isinstance(self.cleanups[0], Dummy)161                and self.compare_vars(self.cleanups[0].var, arg))162    # Check whether SELF is empty.163    def isempty(self):164        log('isempty: len = %d' % len(self.cleanups), 4)165        return len(self.cleanups) == 0166    # Emit informational warnings about the cleanup stack.167    def inform(self):168        for item in reversed(self.cleanups):169            gcc.inform(item.location, 'leaked cleanup')170class CleanupChecker:171    def __init__(self, fun):172        self.fun = fun173        self.seen_edges = set()174        self.bad_returns = set()175        # This maps BB indices to a list of master cleanups for the176        # BB.177        self.master_cleanups = {}178    # Pick a reasonable location for the basic block BB.179    def guess_bb_location(self, bb):180        if isinstance(bb.gimple, list):181            for stmt in bb.gimple:182                if stmt.loc:183                    return stmt.loc184        return self.fun.end185    # Compute the master cleanup list for BB.186    # Modifies MASTER_CLEANUP in place.187    def compute_master(self, bb, bb_from, master_cleanup):188        if not isinstance(bb.gimple, list):189            return190        curloc = self.fun.end191        for stmt in bb.gimple:192            if stmt.loc:193                curloc = stmt.loc194            if isinstance(stmt, gcc.GimpleCall) and stmt.fndecl:195                if is_constructor(stmt.fndecl):196                    log('saw constructor %s in bb=%d' % (str(stmt.fndecl), bb.index), 2)197                    self.cleanup_aware = True198                    master_cleanup.push(curloc, stmt.lhs)199                elif is_destructor(stmt.fndecl):200                    if str(stmt.fndecl.name) != 'do_cleanups':201                        self.only_do_cleanups_seen = False202                    log('saw destructor %s in bb=%d, bb_from=%d, argument=%s'203                        % (str(stmt.fndecl.name), bb.index, bb_from, str(stmt.args[0])),204                        2)205                    master_cleanup.pop(curloc, stmt.args[0])206                elif needs_special_treatment(stmt.fndecl):207                    pass208                    # gcc.permerror(curloc, 'function needs special treatment')209            elif isinstance(stmt, gcc.GimpleAssign):210                if isinstance(stmt.lhs, gcc.VarDecl) and isinstance(stmt.rhs[0], gcc.VarDecl):211                    master_cleanup.note_assignment(stmt.lhs, stmt.rhs[0])212            elif isinstance(stmt, gcc.GimpleReturn):213                if self.is_constructor:214                    if not master_cleanup.verify(curloc, stmt.retval):215                        gcc.permerror(curloc,216                                      'constructor does not return master cleanup')217                elif not self.is_special_constructor:218                    if not master_cleanup.isempty():219                        if curloc not in self.bad_returns:220                            gcc.permerror(curloc, 'cleanup stack is not empty at return')221                            self.bad_returns.add(curloc)222                            master_cleanup.inform()223    # Traverse a basic block, updating the master cleanup information224    # and propagating to other blocks.225    def traverse_bbs(self, edge, bb, bb_from, entry_master):226        log('traverse_bbs %d from %d' % (bb.index, bb_from), 1)227        # Propagate the entry MasterCleanup though this block.228        master_cleanup = MasterCleanup(entry_master)229        self.compute_master(bb, bb_from, master_cleanup)230        modified = False231        if bb.index in self.master_cleanups:232            # Merge the newly-computed MasterCleanup into the one we233            # have already computed.  If this resulted in a234            # significant change, then we need to re-propagate.235            modified = self.master_cleanups[bb.index].merge(master_cleanup)236        else:237            self.master_cleanups[bb.index] = master_cleanup238            modified = True239        # EDGE is None for the entry BB.240        if edge is not None:241            # If merging cleanups caused a change, check to see if we242            # have a bad loop.243            if edge in self.seen_edges:244                # This error doesn't really help.245                # if modified:246                #     gcc.permerror(self.guess_bb_location(bb),247                #                   'invalid cleanup use in loop')248                return249            self.seen_edges.add(edge)250        if not modified:251            return252        # Now propagate to successor nodes.253        for edge in bb.succs:254            self.traverse_bbs(edge, edge.dest, bb.index, master_cleanup)255    def check_cleanups(self):256        if not self.fun.cfg or not self.fun.decl:257            return 'ignored'258        if is_destructor(self.fun.decl):259            return 'destructor'260        if needs_special_treatment(self.fun.decl):261            return 'special'262        self.is_constructor = is_constructor(self.fun.decl)263        self.is_special_constructor = not self.is_constructor and str(self.fun.decl.name).find('with_cleanup') > -1264        # Yuck.265        if str(self.fun.decl.name) == 'gdb_xml_create_parser_and_cleanup_1':266            self.is_special_constructor = True267        if self.is_special_constructor:268            gcc.inform(self.fun.start, 'function %s is a special constructor' % (self.fun.decl.name))269        # If we only see do_cleanups calls, and this function is not270        # itself a constructor, then we can convert it easily to RAII.271        self.only_do_cleanups_seen = not self.is_constructor272        # If we ever call a constructor, then we are "cleanup-aware".273        self.cleanup_aware = False274        entry_bb = self.fun.cfg.entry275        master_cleanup = MasterCleanup()276        self.traverse_bbs(None, entry_bb, -1, master_cleanup)277        if want_raii_info and self.only_do_cleanups_seen and self.cleanup_aware:278            gcc.inform(self.fun.decl.location,279                       'function %s could be converted to RAII' % (self.fun.decl.name))280        if self.is_constructor:281            return 'constructor'282        return 'OK'283class CheckerPass(gcc.GimplePass):284    def execute(self, fun):285        if fun.decl:286            log("Starting " + fun.decl.name)287            if show_cfg:288                dot = gccutils.cfg_to_dot(fun.cfg, fun.decl.name)289                gccutils.invoke_dot(dot, name=fun.decl.name)290        checker = CleanupChecker(fun)291        what = checker.check_cleanups()292        if fun.decl:293            log(fun.decl.name + ': ' + what, 2)294ps = CheckerPass(name = 'check-cleanups')295# We need the cfg, but we want a relatively high-level Gimple....

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