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336 lines
13 KiB
Python
336 lines
13 KiB
Python
# Copyright 2013-2017 Free Software Foundation, Inc.
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#
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# This is free software: you can redistribute it and/or modify it
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# under the terms of the GNU General Public License as published by
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# the Free Software Foundation, either version 3 of the License, or
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# (at your option) any later version.
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#
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# This program is distributed in the hope that it will be useful, but
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# WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# General Public License for more details.
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#
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# You should have received a copy of the GNU General Public License
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# along with this program. If not, see
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# <http://www.gnu.org/licenses/>.
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import gcc
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import gccutils
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import sys
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want_raii_info = False
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logging = False
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show_cfg = False
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def log(msg, indent=0):
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global logging
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if logging:
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sys.stderr.write('%s%s\n' % (' ' * indent, msg))
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sys.stderr.flush()
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def is_cleanup_type(return_type):
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if not isinstance(return_type, gcc.PointerType):
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return False
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if not isinstance(return_type.dereference, gcc.RecordType):
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return False
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if str(return_type.dereference.name) == 'cleanup':
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return True
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return False
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def is_constructor(decl):
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"Return True if the function DECL is a cleanup constructor; False otherwise"
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return is_cleanup_type(decl.type.type) and (not decl.name or str(decl.name) != 'make_final_cleanup')
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destructor_names = set(['do_cleanups', 'discard_cleanups'])
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def is_destructor(decl):
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return decl.name in destructor_names
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# This list is just much too long... we should probably have an
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# attribute instead.
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special_names = set(['do_final_cleanups', 'discard_final_cleanups',
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'save_cleanups', 'save_final_cleanups',
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'restore_cleanups', 'restore_final_cleanups',
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'exceptions_state_mc_init',
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'make_my_cleanup2', 'make_final_cleanup', 'all_cleanups',
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'save_my_cleanups', 'quit_target'])
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def needs_special_treatment(decl):
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return decl.name in special_names
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# Sometimes we need a new placeholder object that isn't the same as
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# anything else.
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class Dummy(object):
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def __init__(self, location):
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self.location = location
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# A wrapper for a cleanup which has been assigned to a variable.
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# This holds the variable and the location.
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class Cleanup(object):
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def __init__(self, var, location):
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self.var = var
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self.location = location
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# A class representing a master cleanup. This holds a stack of
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# cleanup objects and supports a merging operation.
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class MasterCleanup(object):
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# Create a new MasterCleanup object. OTHER, if given, is a
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# MasterCleanup object to copy.
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def __init__(self, other = None):
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# 'cleanups' is a list of cleanups. Each element is either a
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# Dummy, for an anonymous cleanup, or a Cleanup, for a cleanup
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# which was assigned to a variable.
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if other is None:
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self.cleanups = []
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self.aliases = {}
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else:
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self.cleanups = other.cleanups[:]
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self.aliases = dict(other.aliases)
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def compare_vars(self, definition, argument):
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if definition == argument:
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return True
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if argument in self.aliases:
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argument = self.aliases[argument]
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if definition in self.aliases:
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definition = self.aliases[definition]
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return definition == argument
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def note_assignment(self, lhs, rhs):
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log('noting assignment %s = %s' % (lhs, rhs), 4)
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self.aliases[lhs] = rhs
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# Merge with another MasterCleanup.
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# Returns True if this resulted in a change to our state.
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def merge(self, other):
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# We do explicit iteration like this so we can easily
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# update the list after the loop.
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counter = -1
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found_named = False
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for counter in range(len(self.cleanups) - 1, -1, -1):
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var = self.cleanups[counter]
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log('merge checking %s' % var, 4)
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# Only interested in named cleanups.
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if isinstance(var, Dummy):
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log('=> merge dummy', 5)
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continue
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# Now see if VAR is found in OTHER.
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if other._find_var(var.var) >= 0:
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log ('=> merge found', 5)
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break
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log('=>merge not found', 5)
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found_named = True
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if found_named and counter < len(self.cleanups) - 1:
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log ('merging to %d' % counter, 4)
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if counter < 0:
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self.cleanups = []
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else:
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self.cleanups = self.cleanups[0:counter]
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return True
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# If SELF is empty but OTHER has some cleanups, then consider
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# that a change as well.
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if len(self.cleanups) == 0 and len(other.cleanups) > 0:
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log('merging non-empty other', 4)
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self.cleanups = other.cleanups[:]
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return True
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return False
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# Push a new constructor onto our stack. LHS is the
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# left-hand-side of the GimpleCall statement. It may be None,
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# meaning that this constructor's value wasn't used.
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def push(self, location, lhs):
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if lhs is None:
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obj = Dummy(location)
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else:
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obj = Cleanup(lhs, location)
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log('pushing %s' % lhs, 4)
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idx = self._find_var(lhs)
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if idx >= 0:
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gcc.permerror(location, 'reassigning to known cleanup')
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gcc.inform(self.cleanups[idx].location,
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'previous assignment is here')
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self.cleanups.append(obj)
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# A helper for merge and pop that finds BACK_TO in self.cleanups,
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# and returns the index, or -1 if not found.
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def _find_var(self, back_to):
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for i in range(len(self.cleanups) - 1, -1, -1):
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if isinstance(self.cleanups[i], Dummy):
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continue
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if self.compare_vars(self.cleanups[i].var, back_to):
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return i
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return -1
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# Pop constructors until we find one matching BACK_TO.
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# This is invoked when we see a do_cleanups call.
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def pop(self, location, back_to):
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log('pop:', 4)
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i = self._find_var(back_to)
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if i >= 0:
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self.cleanups = self.cleanups[0:i]
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else:
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gcc.permerror(location, 'destructor call with unknown argument')
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# Check whether ARG is the current master cleanup. Return True if
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# all is well.
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def verify(self, location, arg):
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log('verify %s' % arg, 4)
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return (len(self.cleanups) > 0
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and not isinstance(self.cleanups[0], Dummy)
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and self.compare_vars(self.cleanups[0].var, arg))
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# Check whether SELF is empty.
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def isempty(self):
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log('isempty: len = %d' % len(self.cleanups), 4)
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return len(self.cleanups) == 0
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# Emit informational warnings about the cleanup stack.
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def inform(self):
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for item in reversed(self.cleanups):
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gcc.inform(item.location, 'leaked cleanup')
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class CleanupChecker:
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def __init__(self, fun):
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self.fun = fun
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self.seen_edges = set()
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self.bad_returns = set()
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# This maps BB indices to a list of master cleanups for the
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# BB.
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self.master_cleanups = {}
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# Pick a reasonable location for the basic block BB.
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def guess_bb_location(self, bb):
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if isinstance(bb.gimple, list):
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for stmt in bb.gimple:
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if stmt.loc:
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return stmt.loc
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return self.fun.end
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# Compute the master cleanup list for BB.
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# Modifies MASTER_CLEANUP in place.
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def compute_master(self, bb, bb_from, master_cleanup):
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if not isinstance(bb.gimple, list):
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return
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curloc = self.fun.end
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for stmt in bb.gimple:
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if stmt.loc:
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curloc = stmt.loc
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if isinstance(stmt, gcc.GimpleCall) and stmt.fndecl:
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if is_constructor(stmt.fndecl):
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log('saw constructor %s in bb=%d' % (str(stmt.fndecl), bb.index), 2)
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self.cleanup_aware = True
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master_cleanup.push(curloc, stmt.lhs)
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elif is_destructor(stmt.fndecl):
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if str(stmt.fndecl.name) != 'do_cleanups':
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self.only_do_cleanups_seen = False
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log('saw destructor %s in bb=%d, bb_from=%d, argument=%s'
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% (str(stmt.fndecl.name), bb.index, bb_from, str(stmt.args[0])),
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2)
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master_cleanup.pop(curloc, stmt.args[0])
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elif needs_special_treatment(stmt.fndecl):
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pass
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# gcc.permerror(curloc, 'function needs special treatment')
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elif isinstance(stmt, gcc.GimpleAssign):
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if isinstance(stmt.lhs, gcc.VarDecl) and isinstance(stmt.rhs[0], gcc.VarDecl):
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master_cleanup.note_assignment(stmt.lhs, stmt.rhs[0])
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elif isinstance(stmt, gcc.GimpleReturn):
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if self.is_constructor:
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if not master_cleanup.verify(curloc, stmt.retval):
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gcc.permerror(curloc,
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'constructor does not return master cleanup')
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elif not self.is_special_constructor:
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if not master_cleanup.isempty():
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if curloc not in self.bad_returns:
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gcc.permerror(curloc, 'cleanup stack is not empty at return')
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self.bad_returns.add(curloc)
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master_cleanup.inform()
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# Traverse a basic block, updating the master cleanup information
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# and propagating to other blocks.
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def traverse_bbs(self, edge, bb, bb_from, entry_master):
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log('traverse_bbs %d from %d' % (bb.index, bb_from), 1)
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# Propagate the entry MasterCleanup though this block.
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master_cleanup = MasterCleanup(entry_master)
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self.compute_master(bb, bb_from, master_cleanup)
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modified = False
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if bb.index in self.master_cleanups:
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# Merge the newly-computed MasterCleanup into the one we
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# have already computed. If this resulted in a
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# significant change, then we need to re-propagate.
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modified = self.master_cleanups[bb.index].merge(master_cleanup)
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else:
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self.master_cleanups[bb.index] = master_cleanup
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modified = True
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# EDGE is None for the entry BB.
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if edge is not None:
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# If merging cleanups caused a change, check to see if we
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# have a bad loop.
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if edge in self.seen_edges:
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# This error doesn't really help.
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# if modified:
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# gcc.permerror(self.guess_bb_location(bb),
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# 'invalid cleanup use in loop')
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return
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self.seen_edges.add(edge)
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if not modified:
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return
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# Now propagate to successor nodes.
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for edge in bb.succs:
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self.traverse_bbs(edge, edge.dest, bb.index, master_cleanup)
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def check_cleanups(self):
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if not self.fun.cfg or not self.fun.decl:
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return 'ignored'
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if is_destructor(self.fun.decl):
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return 'destructor'
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if needs_special_treatment(self.fun.decl):
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return 'special'
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self.is_constructor = is_constructor(self.fun.decl)
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self.is_special_constructor = not self.is_constructor and str(self.fun.decl.name).find('with_cleanup') > -1
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# Yuck.
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if str(self.fun.decl.name) == 'gdb_xml_create_parser_and_cleanup_1':
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self.is_special_constructor = True
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if self.is_special_constructor:
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gcc.inform(self.fun.start, 'function %s is a special constructor' % (self.fun.decl.name))
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# If we only see do_cleanups calls, and this function is not
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# itself a constructor, then we can convert it easily to RAII.
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self.only_do_cleanups_seen = not self.is_constructor
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# If we ever call a constructor, then we are "cleanup-aware".
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self.cleanup_aware = False
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entry_bb = self.fun.cfg.entry
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master_cleanup = MasterCleanup()
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self.traverse_bbs(None, entry_bb, -1, master_cleanup)
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if want_raii_info and self.only_do_cleanups_seen and self.cleanup_aware:
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gcc.inform(self.fun.decl.location,
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'function %s could be converted to RAII' % (self.fun.decl.name))
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if self.is_constructor:
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return 'constructor'
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return 'OK'
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class CheckerPass(gcc.GimplePass):
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def execute(self, fun):
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if fun.decl:
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log("Starting " + fun.decl.name)
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if show_cfg:
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dot = gccutils.cfg_to_dot(fun.cfg, fun.decl.name)
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gccutils.invoke_dot(dot, name=fun.decl.name)
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checker = CleanupChecker(fun)
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what = checker.check_cleanups()
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if fun.decl:
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log(fun.decl.name + ': ' + what, 2)
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ps = CheckerPass(name = 'check-cleanups')
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# We need the cfg, but we want a relatively high-level Gimple.
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ps.register_after('cfg')
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