cprover
symex_start_thread.cpp
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1 /*******************************************************************\
2 
3 Module: Symbolic Execution
4 
5 Author: Daniel Kroening, kroening@kroening.com
6 
7 \*******************************************************************/
8 
11 
12 #include "goto_symex.h"
13 
14 #include <util/exception_utils.h>
15 #include <util/expr_initializer.h>
16 
17 #include "expr_skeleton.h"
18 #include "symex_assign.h"
19 
21 {
22  if(!state.reachable)
23  return;
24 
25  if(state.atomic_section_id != 0)
27  "spawning threads out of atomic sections is not allowed; "
28  "this would require amendments to ordering constraints",
29  state.source.pc->source_location);
30 
31  // record this
32  target.spawn(state.guard.as_expr(), state.source);
33 
34  const goto_programt::instructiont &instruction=*state.source.pc;
35 
36  INVARIANT(instruction.targets.size() == 1, "start_thread expects one target");
37 
38  goto_programt::const_targett thread_target=
39  instruction.get_target();
40 
41  // put into thread vector
42  std::size_t t=state.threads.size();
43  state.threads.push_back(statet::threadt(guard_manager));
44  // statet::threadt &cur_thread=state.threads[state.source.thread_nr];
45  statet::threadt &new_thread=state.threads.back();
46  new_thread.pc=thread_target;
47  new_thread.guard=state.guard;
48  new_thread.call_stack.push_back(state.call_stack().top());
49  new_thread.call_stack.back().local_objects.clear();
50  new_thread.call_stack.back().goto_state_map.clear();
51  #if 0
52  new_thread.abstract_events=&(target.new_thread(cur_thread.abstract_events));
53  #endif
54 
55  // create a copy of the local variables for the new thread
56  framet &frame = state.call_stack().top();
57 
59  state.get_level2().current_names.get_view(view);
60 
61  for(const auto &pair : view)
62  {
63  const irep_idt l1_o_id = pair.second.first.get_l1_object_identifier();
64 
65  // could use iteration over local_objects as l1_o_id is prefix
66  if(frame.local_objects.find(l1_o_id)==frame.local_objects.end())
67  continue;
68 
69  // get original name
70  ssa_exprt lhs(pair.second.first.get_original_expr());
71 
72  // get L0 name for current thread
73  const renamedt<ssa_exprt, L0> l0_lhs = symex_level0(std::move(lhs), ns, t);
74  const irep_idt &l0_name = l0_lhs.get().get_identifier();
75  std::size_t l1_index = path_storage.get_unique_l1_index(l0_name, 0);
76  CHECK_RETURN(l1_index == 0);
77 
78  // set up L1 name
79  state.level1.insert(l0_lhs, 0);
80 
81  const ssa_exprt lhs_l1 = state.rename_ssa<L1>(l0_lhs.get(), ns).get();
82  const irep_idt l1_name = lhs_l1.get_l1_object_identifier();
83  // store it
84  new_thread.call_stack.back().local_objects.insert(l1_name);
85 
86  // make copy
87  ssa_exprt rhs = pair.second.first;
88 
89  exprt::operandst lhs_conditions;
90  state.record_events.push(false);
93  .assign_symbol(lhs_l1, expr_skeletont{}, rhs, lhs_conditions);
94  state.record_events.pop();
95  }
96 
97  // initialize all variables marked thread-local
98  const symbol_tablet &symbol_table=ns.get_symbol_table();
99 
100  for(const auto &symbol_pair : symbol_table.symbols)
101  {
102  const symbolt &symbol = symbol_pair.second;
103 
104  if(!symbol.is_thread_local ||
105  !symbol.is_static_lifetime ||
106  (symbol.is_extern && symbol.value.is_nil()))
107  continue;
108 
109  // get original name
110  ssa_exprt lhs(symbol.symbol_expr());
111 
112  // get L0 name for current thread
113  lhs.set_level_0(t);
114 
115  exprt rhs=symbol.value;
116  if(rhs.is_nil())
117  {
118  const auto zero = zero_initializer(symbol.type, symbol.location, ns);
119  CHECK_RETURN(zero.has_value());
120  rhs = *zero;
121  }
122 
123  exprt::operandst lhs_conditions;
126  .assign_symbol(lhs, expr_skeletont{}, rhs, lhs_conditions);
127  }
128 }
framet & top()
Definition: call_stack.h:17
dstringt has one field, an unsigned integer no which is an index into a static table of strings.
Definition: dstring.h:37
Expression in which some part is missing and can be substituted for another expression.
Definition: expr_skeleton.h:26
Base class for all expressions.
Definition: expr.h:54
std::vector< exprt > operandst
Definition: expr.h:56
This class represents an instruction in the GOTO intermediate representation.
Definition: goto_program.h:180
targetst targets
The list of successor instructions.
Definition: goto_program.h:371
targett get_target() const
Returns the first (and only) successor for the usual case of a single target.
Definition: goto_program.h:375
instructionst::const_iterator const_targett
Definition: goto_program.h:551
guardt guard
Definition: goto_state.h:54
bool reachable
Is this code reachable? If not we can take shortcuts such as not entering function calls,...
Definition: goto_state.h:58
unsigned atomic_section_id
Threads.
Definition: goto_state.h:72
const symex_level2t & get_level2() const
Definition: goto_state.h:41
Central data structure: state.
std::stack< bool > record_events
call_stackt & call_stack()
symex_level1t level1
NODISCARD renamedt< ssa_exprt, level > rename_ssa(ssa_exprt ssa, const namespacet &ns)
Version of rename which is specialized for SSA exprt.
symex_targett::sourcet source
std::vector< threadt > threads
path_storaget & path_storage
Symbolic execution paths to be resumed later.
Definition: goto_symex.h:797
symex_target_equationt & target
The equation that this execution is building up.
Definition: goto_symex.h:264
guard_managert & guard_manager
Used to create guards.
Definition: goto_symex.h:261
virtual void symex_start_thread(statet &state)
Symbolically execute a START_THREAD instruction.
namespacet ns
Initialized just before symbolic execution begins, to point to both outer_symbol_table and the symbol...
Definition: goto_symex.h:256
const symex_configt symex_config
The configuration to use for this symbolic execution.
Definition: goto_symex.h:183
exprt as_expr() const
Definition: guard_expr.h:49
Thrown when a goto program that's being processed is in an invalid format, for example passing the wr...
bool is_nil() const
Definition: irep.h:387
const symbol_table_baset & get_symbol_table() const
Return first symbol table registered with the namespace.
Definition: namespace.h:124
std::size_t get_unique_l1_index(const irep_idt &id, std::size_t minimum_index)
Provide a unique L1 index for a given id, starting from minimum_index.
Definition: path_storage.h:104
Wrapper for expressions or types which have been renamed up to a given level.
Definition: renamed.h:27
const underlyingt & get() const
Definition: renamed.h:34
std::vector< view_itemt > viewt
View of the key-value pairs in the map.
Definition: sharing_map.h:388
void get_view(V &view) const
Get a view of the elements in the map A view is a list of pairs with the components being const refer...
Expression providing an SSA-renamed symbol of expressions.
Definition: ssa_expr.h:17
const irep_idt get_l1_object_identifier() const
void set_level_0(std::size_t i)
const symbolst & symbols
Read-only field, used to look up symbols given their names.
The symbol table.
Definition: symbol_table.h:20
Symbol table entry.
Definition: symbol.h:28
bool is_extern
Definition: symbol.h:66
bool is_static_lifetime
Definition: symbol.h:65
bool is_thread_local
Definition: symbol.h:65
source_locationt location
Source code location of definition of symbol.
Definition: symbol.h:37
class symbol_exprt symbol_expr() const
Produces a symbol_exprt for a symbol.
Definition: symbol.cpp:122
typet type
Type of symbol.
Definition: symbol.h:31
exprt value
Initial value of symbol.
Definition: symbol.h:34
Functor for symex assignment.
Definition: symex_assign.h:26
virtual void spawn(const exprt &guard, const sourcet &source)
Record spawning a new thread.
optionalt< exprt > zero_initializer(const typet &type, const source_locationt &source_location, const namespacet &ns)
Create the equivalent of zero for type type.
Expression Initialization.
Expression skeleton.
Symbolic Execution.
@ L1
Definition: renamed.h:18
renamedt< ssa_exprt, L0 > symex_level0(ssa_exprt ssa_expr, const namespacet &ns, std::size_t thread_nr)
Set the level 0 renaming of SSA expressions.
#define CHECK_RETURN(CONDITION)
Definition: invariant.h:496
Stack frames – these are used for function calls and for exceptions.
Definition: frame.h:21
std::set< irep_idt > local_objects
Definition: frame.h:38
goto_programt::const_targett pc
void insert(const renamedt< ssa_exprt, L0 > &ssa, std::size_t index)
Assume ssa is not already known.
symex_renaming_levelt current_names
goto_programt::const_targett pc
Definition: symex_target.h:43
Symbolic Execution of assignments.