CBMC
model_argc_argv.cpp
Go to the documentation of this file.
1 /*******************************************************************\
2 
3 Module: Initialize command line arguments
4 
5 Author: Michael Tautschnig
6 
7 Date: April 2016
8 
9 \*******************************************************************/
10 
13 
14 #include "model_argc_argv.h"
15 
16 #include <util/config.h>
17 #include <util/cprover_prefix.h>
18 #include <util/invariant.h>
19 #include <util/message.h>
20 #include <util/namespace.h>
21 #include <util/prefix.h>
22 #include <util/replace_symbol.h>
23 #include <util/symbol_table.h>
24 
27 
28 #include <ansi-c/ansi_c_language.h>
30 
31 #include <sstream>
32 
40  goto_modelt &goto_model,
41  unsigned max_argc,
42  message_handlert &message_handler)
43 {
44  messaget message(message_handler);
45  const namespacet ns(goto_model.symbol_table);
46 
47  if(!goto_model.symbol_table.has_symbol(
48  goto_model.goto_functions.entry_point()))
49  {
50  message.error() << "Linking not done, missing "
51  << goto_model.goto_functions.entry_point()
52  << messaget::eom;
53  return true;
54  }
55 
56  const symbolt &main_symbol =
57  ns.lookup(config.main.has_value() ? config.main.value() : ID_main);
58 
59  if(main_symbol.mode!=ID_C)
60  {
61  message.error() << "argc/argv modelling is C specific"
62  << messaget::eom;
63  return true;
64  }
65 
66  const code_typet::parameterst &parameters=
67  to_code_type(main_symbol.type).parameters();
68  if(parameters.size()!=2 &&
69  parameters.size()!=3)
70  {
71  message.warning() << "main expected to take 2 or 3 arguments,"
72  << " argc/argv instrumentation skipped"
73  << messaget::eom;
74  return false;
75  }
76 
77  const symbolt &argc_primed = ns.lookup("argc'");
78  symbol_exprt ARGC("ARGC", argc_primed.type);
79  const symbolt &argv_primed = ns.lookup("argv'");
80  symbol_exprt ARGV("ARGV", argv_primed.type);
81 
82  // set the size of ARGV storage to 4096, which matches the minimum
83  // guaranteed by POSIX (_POSIX_ARG_MAX):
84  // http://pubs.opengroup.org/onlinepubs/009695399/basedefs/limits.h.html
85  std::ostringstream oss;
86  oss << "int ARGC;\n"
87  << "char *ARGV[1];\n"
88  << "extern char " CPROVER_PREFIX "arg_string[4096];\n"
89  << "void " << goto_model.goto_functions.entry_point() << "()\n"
90  << "{\n"
91  << " unsigned next=0u;\n"
92  << " " CPROVER_PREFIX "assume(ARGC>=1);\n"
93  << " " CPROVER_PREFIX "assume(ARGC<=" << max_argc << ");\n"
94  << " " CPROVER_PREFIX "input(\"arg_string\", \n"
95  << " &" CPROVER_PREFIX "arg_string[0]);\n"
96  << " for(int i=0; i<ARGC && i<" << max_argc << "; ++i)\n"
97  << " {\n"
98  << " unsigned len;\n"
99  << " " CPROVER_PREFIX "assume(len<4096);\n"
100  << " " CPROVER_PREFIX "assume(next+len<4096);\n"
101  << " " CPROVER_PREFIX "assume(\n"
102  << " " CPROVER_PREFIX "arg_string[next+len]==0);\n"
103  << " ARGV[i]=&(" CPROVER_PREFIX "arg_string[next]);\n"
104  << " next+=len+1;\n"
105  << " }\n"
106  << "}";
107  std::istringstream iss(oss.str());
108 
109  ansi_c_languaget ansi_c_language;
112  ansi_c_language.parse(iss, "", message_handler);
114 
115  symbol_tablet tmp_symbol_table;
116  ansi_c_language.typecheck(
117  tmp_symbol_table, "<built-in-library>", message_handler);
118 
119  goto_programt init_instructions;
120  exprt value=nil_exprt();
121  // locate the body of the newly built start function as well as any
122  // additional declarations we might need; the body will then be
123  // converted and inserted into the start function
124  for(const auto &symbol_pair : tmp_symbol_table.symbols)
125  {
126  // add __CPROVER_assume if necessary (it might exist already)
127  if(
128  symbol_pair.first == CPROVER_PREFIX "assume" ||
129  symbol_pair.first == CPROVER_PREFIX "input" ||
130  symbol_pair.first == CPROVER_PREFIX "arg_string")
131  {
132  goto_model.symbol_table.add(symbol_pair.second);
133  }
134  else if(symbol_pair.first == goto_model.goto_functions.entry_point())
135  {
136  value = symbol_pair.second.value;
137 
139  replace.insert(ARGC, ns.lookup("argc'").symbol_expr());
140  replace.insert(ARGV, ns.lookup("argv'").symbol_expr());
141  replace(value);
142  }
143  else if(
144  has_prefix(
145  id2string(symbol_pair.first),
146  id2string(goto_model.goto_functions.entry_point()) + "::") &&
147  goto_model.symbol_table.add(symbol_pair.second))
148  UNREACHABLE;
149  }
150  POSTCONDITION(value.is_not_nil());
151 
152  goto_convert(
153  to_code(value),
154  goto_model.symbol_table,
155  init_instructions,
156  message_handler,
157  main_symbol.mode);
158 
159  for(auto &instruction : init_instructions.instructions)
160  instruction.source_location_nonconst().set_file("<built-in-library>");
161 
162  goto_functionst::function_mapt::iterator start_entry=
163  goto_model.goto_functions.function_map.find(
164  goto_model.goto_functions.entry_point());
165 
167  start_entry!=goto_model.goto_functions.function_map.end() &&
168  start_entry->second.body_available(),
169  "entry point expected to have a body");
170 
171  goto_programt &start=start_entry->second.body;
172  goto_programt::targett main_call=start.instructions.begin();
173  for(goto_programt::targett end=start.instructions.end();
174  main_call!=end;
175  ++main_call)
176  {
177  if(main_call->is_function_call())
178  {
179  const exprt &func = main_call->call_function();
180  if(func.id()==ID_symbol &&
181  to_symbol_expr(func).get_identifier()==main_symbol.name)
182  break;
183  }
184  }
185  POSTCONDITION(main_call!=start.instructions.end());
186 
187  start.insert_before_swap(main_call, init_instructions);
188 
189  // update counters etc.
190  remove_skip(start);
191 
192  return false;
193 }
configt config
Definition: config.cpp:25
bool typecheck(symbol_table_baset &symbol_table, const std::string &module, message_handlert &message_handler, const bool keep_file_local) override
typecheck without removing specified entries from the symbol table
bool parse(std::istream &instream, const std::string &path, message_handlert &message_handler) override
std::vector< parametert > parameterst
Definition: std_types.h:585
const parameterst & parameters() const
Definition: std_types.h:699
std::optional< std::string > main
Definition: config.h:360
struct configt::ansi_ct ansi_c
Base class for all expressions.
Definition: expr.h:56
function_mapt function_map
static irep_idt entry_point()
Get the identifier of the entry point to a goto model.
symbol_tablet symbol_table
Symbol table.
Definition: goto_model.h:31
goto_functionst goto_functions
GOTO functions.
Definition: goto_model.h:34
A generic container class for the GOTO intermediate representation of one function.
Definition: goto_program.h:73
instructionst instructions
The list of instructions in the goto program.
Definition: goto_program.h:622
void insert_before_swap(targett target)
Insertion that preserves jumps to "target".
Definition: goto_program.h:643
instructionst::iterator targett
Definition: goto_program.h:614
bool is_not_nil() const
Definition: irep.h:372
const irep_idt & id() const
Definition: irep.h:388
Class that provides messages with a built-in verbosity 'level'.
Definition: message.h:154
mstreamt & error() const
Definition: message.h:391
mstreamt & warning() const
Definition: message.h:396
static eomt eom
Definition: message.h:289
A namespacet is essentially one or two symbol tables bound together, to allow for symbol lookups in t...
Definition: namespace.h:94
bool lookup(const irep_idt &name, const symbolt *&symbol) const override
See documentation for namespace_baset::lookup().
Definition: namespace.cpp:148
The NIL expression.
Definition: std_expr.h:3081
Expression to hold a symbol (variable)
Definition: std_expr.h:131
const symbolst & symbols
Read-only field, used to look up symbols given their names.
bool has_symbol(const irep_idt &name) const
Check whether a symbol exists in the symbol table.
bool add(const symbolt &symbol)
Add a new symbol to the symbol table.
The symbol table.
Definition: symbol_table.h:14
Symbol table entry.
Definition: symbol.h:28
typet type
Type of symbol.
Definition: symbol.h:31
irep_idt name
The unique identifier.
Definition: symbol.h:40
irep_idt mode
Language mode.
Definition: symbol.h:49
bool has_prefix(const std::string &s, const std::string &prefix)
Definition: converter.cpp:13
#define CPROVER_PREFIX
void goto_convert(const codet &code, symbol_table_baset &symbol_table, goto_programt &dest, message_handlert &message_handler, const irep_idt &mode)
Program Transformation.
Symbol Table + CFG.
const std::string & id2string(const irep_idt &d)
Definition: irep.h:44
bool model_argc_argv(goto_modelt &goto_model, unsigned max_argc, message_handlert &message_handler)
Set up argv with up to max_argc pointers into an array of 4096 bytes.
Initialize command line arguments.
void remove_skip(goto_programt &goto_program, goto_programt::targett begin, goto_programt::targett end)
remove unnecessary skip statements
Definition: remove_skip.cpp:87
Program Transformation.
#define UNREACHABLE
This should be used to mark dead code.
Definition: invariant.h:525
#define DATA_INVARIANT(CONDITION, REASON)
This condition should be used to document that assumptions that are made on goto_functions,...
Definition: invariant.h:534
#define POSTCONDITION(CONDITION)
Definition: invariant.h:479
const codet & to_code(const exprt &expr)
const symbol_exprt & to_symbol_expr(const exprt &expr)
Cast an exprt to a symbol_exprt.
Definition: std_expr.h:272
const code_typet & to_code_type(const typet &type)
Cast a typet to a code_typet.
Definition: std_types.h:788
void replace(const union_find_replacet &replace_map, string_not_contains_constraintt &constraint)
preprocessort preprocessor
Definition: config.h:267
Author: Diffblue Ltd.