goto-instrument --model-argc-argv: Explicitly initialise argc, argv

Warn when --model-argc-argv is used for main functions without arguments

Author: tautschnig

regression/goto-instrument/argc-argv1/main.c

@@ -0,0 +1,9 @@
+#include <assert.h>
+
+int main(int argc, char* argv[])
+{
+  if(argc>=2)
+    assert(argv[1]!=0);
+
+  return 0;
+}

regression/goto-instrument/argc-argv1/test.desc

@@ -0,0 +1,8 @@
+CORE
+main.c
+--model-argc-argv 2
+^EXIT=0$
+^SIGNAL=0$
+^VERIFICATION SUCCESSFUL$
+--
+^warning: ignoring

src/goto-instrument/Makefile

@@ -23,7 +23,7 @@ SRC = goto_instrument_parse_options.cpp rw_set.cpp \
       wmm/event_graph.cpp wmm/pair_collection.cpp \
       goto_instrument_main.cpp horn_encoding.cpp \
       thread_instrumentation.cpp skip_loops.cpp loop_utils.cpp \
-      code_contracts.cpp cover.cpp
+      code_contracts.cpp cover.cpp model_argc_argv.cpp
 
 OBJ += ../ansi-c/ansi-c$(LIBEXT) \
       ../cpp/cpp$(LIBEXT) \

src/goto-instrument/goto_instrument_parse_options.cpp

@@ -85,6 +85,7 @@ Author: Daniel Kroening, [email protected]
 #include "skip_loops.h"
 #include "code_contracts.h"
 #include "unwind.h"
+#include "model_argc_argv.h"
 
 /*******************************************************************\
 
@@ -920,6 +921,24 @@ void goto_instrument_parse_optionst::instrument_goto_program()
       throw 0;
   }
 
+  namespacet ns(symbol_table);
+
+  // initialize argv with valid pointers
+  if(cmdline.isset("model-argc-argv"))
+  {
+    unsigned max_argc=
+      safe_string2unsigned(cmdline.get_value("model-argc-argv"));
+
+    status() << "Adding up to " << max_argc
+             << " command line arguments" << eom;
+    if(model_argc_argv(
+        symbol_table,
+        goto_functions,
+        max_argc,
+        get_message_handler()))
+      throw 0;
+  }
+
   // we add the library in some cases, as some analyses benefit
 
   if(cmdline.isset("add-library") ||
@@ -933,8 +952,6 @@ void goto_instrument_parse_optionst::instrument_goto_program()
     link_to_library(symbol_table, goto_functions, ui_message_handler);
   }
 
-  namespacet ns(symbol_table);
-
   // now do full inlining, if requested
   if(cmdline.isset("inline"))
   {
@@ -1501,6 +1518,7 @@ void goto_instrument_parse_optionst::help()
     " --log <file>                 log in json format which code segments were inlined, use with --function-inline\n" // NOLINT(*)
     " --remove-function-pointers   replace function pointers by case statement over function calls\n" // NOLINT(*)
     " --add-library                add models of C library functions\n"
+    " --model-argc-argv <n>        model up to <n> command line arguments\n"
     "\n"
     "Other options:\n"
     " --use-system-headers         with --dump-c/--dump-cpp: generate C source with includes\n" // NOLINT(*)

src/goto-instrument/goto_instrument_parse_options.h

@@ -65,7 +65,7 @@ Author: Daniel Kroening, [email protected]
   "(interpreter)(show-reaching-definitions)(count-eloc)(list-eloc)" \
   "(list-symbols)(list-undefined-functions)" \
   "(z3)(add-library)(show-dependence-graph)" \
-  "(horn)(skip-loops):(apply-code-contracts)"
+  "(horn)(skip-loops):(apply-code-contracts)(model-argc-argv):"
 
 class goto_instrument_parse_optionst:
   public parse_options_baset,

src/goto-instrument/model_argc_argv.cpp

@@ -0,0 +1,172 @@
+/*******************************************************************\
+
+Module: Initialize command line arguments
+
+Author: Michael Tautschnig
+
+Date: April 2016
+
+\*******************************************************************/
+
+#include <sstream>
+
+#include <util/cprover_prefix.h>
+#include <util/message.h>
+#include <util/namespace.h>
+#include <util/config.h>
+#include <util/replace_symbol.h>
+#include <util/symbol_table.h>
+#include <util/prefix.h>
+
+#include <ansi-c/ansi_c_language.h>
+
+#include <goto-programs/goto_convert.h>
+#include <goto-programs/goto_functions.h>
+#include <goto-programs/remove_skip.h>
+
+#include "model_argc_argv.h"
+
+/*******************************************************************\
+
+Function: model_argc_argv
+
+  Inputs:
+
+ Outputs:
+
+ Purpose:
+
+\*******************************************************************/
+
+bool model_argc_argv(
+  symbol_tablet &symbol_table,
+  goto_functionst &goto_functions,
+  unsigned max_argc,
+  message_handlert &message_handler)
+{
+  messaget message(message_handler);
+  const namespacet ns(symbol_table);
+
+  const symbolt *init_symbol=0;
+  if(ns.lookup(CPROVER_PREFIX "initialize", init_symbol))
+  {
+    message.error() << "Linking not done, missing "
+                    << CPROVER_PREFIX "initialize" << messaget::eom;
+    return true;
+  }
+
+  if(init_symbol->mode!=ID_C)
+  {
+    message.error() << "argc/argv modelling is C specific"
+                    << messaget::eom;
+    return true;
+  }
+
+  goto_functionst::function_mapt::iterator init_entry=
+    goto_functions.function_map.find(CPROVER_PREFIX "initialize");
+  assert(
+    init_entry!=goto_functions.function_map.end() &&
+    init_entry->second.body_available());
+
+  goto_programt &init=init_entry->second.body;
+  goto_programt::targett init_end=init.instructions.end();
+  --init_end;
+  assert(init_end->is_end_function());
+  assert(init_end!=init.instructions.begin());
+  --init_end;
+
+  const symbolt &main_symbol=
+    ns.lookup(config.main.empty()?ID_main:config.main);
+
+  const code_typet::parameterst &parameters=
+    to_code_type(main_symbol.type).parameters();
+  if(parameters.size()!=2 &&
+     parameters.size()!=3)
+  {
+    message.warning() << "main expected to take 2 or 3 arguments,"
+                      << " argc/argv instrumentation skipped"
+                      << messaget::eom;
+    return false;
+  }
+
+  // set the size of ARGV storage to 4096, which matches the minimum
+  // guaranteed by POSIX (_POSIX_ARG_MAX):
+  // http://pubs.opengroup.org/onlinepubs/009695399/basedefs/limits.h.html
+  std::ostringstream oss;
+  oss <<
+    "int ARGC;\n\
+     char *ARGV[1];\n\
+     void " CPROVER_PREFIX "initialize()\n\
+     {\n\
+	     unsigned next=0u;\n\
+       " CPROVER_PREFIX "assume(ARGC>=1);\n\
+       " CPROVER_PREFIX "assume(ARGC<=" << max_argc << ");\n\
+       " CPROVER_PREFIX "thread_local static char arg_string[4096];\n\
+       for(unsigned i=0u; i<ARGC && i<" << max_argc << "; ++i)\n\
+       {\n\
+         unsigned len;\n\
+         " CPROVER_PREFIX "assume(len<4096);\n\
+         " CPROVER_PREFIX "assume(next+len<4096);\n\
+         " CPROVER_PREFIX "assume(arg_string[next+len]==0);\n\
+         ARGV[i]=&(arg_string[next]);\n\
+         next+=len+1;\n\
+       }\n\
+     }";
+  std::istringstream iss(oss.str());
+
+  ansi_c_languaget ansi_c_language;
+  ansi_c_language.set_message_handler(message_handler);
+  configt::ansi_ct::preprocessort pp=config.ansi_c.preprocessor;
+  config.ansi_c.preprocessor=configt::ansi_ct::preprocessort::NONE;
+  ansi_c_language.parse(iss, "");
+  config.ansi_c.preprocessor=pp;
+
+  symbol_tablet tmp_symbol_table;
+  ansi_c_language.typecheck(tmp_symbol_table, "<built-in-library>");
+
+  goto_programt tmp;
+  exprt value=nil_exprt();
+  // locate the body of the newly built initialize function as well
+  // as any additional declarations we might need; the body will then
+  // be converted and appended to the existing initialize function
+  forall_symbols(it, tmp_symbol_table.symbols)
+  {
+    // add __CPROVER_assume if necessary (it might exist already)
+    if(it->first==CPROVER_PREFIX "assume")
+      symbol_table.add(it->second);
+    else if(it->first==CPROVER_PREFIX "initialize")
+    {
+      value=it->second.value;
+
+      replace_symbolt replace;
+      replace.insert("ARGC", ns.lookup("argc'").symbol_expr());
+      replace.insert("ARGV", ns.lookup("argv'").symbol_expr());
+      replace(value);
+    }
+    else if(has_prefix(id2string(it->first),
+                       CPROVER_PREFIX "initialize::") &&
+            symbol_table.add(it->second))
+      assert(false);
+  }
+
+  assert(value.is_not_nil());
+  goto_convert(
+    to_code(value),
+    symbol_table,
+    tmp,
+    message_handler);
+  Forall_goto_program_instructions(it, tmp)
+  {
+    it->source_location.set_file("<built-in-library>");
+    it->function=CPROVER_PREFIX "initialize";
+  }
+  init.insert_before_swap(init_end, tmp);
+
+  // update counters etc.
+  remove_skip(init);
+  init.compute_loop_numbers();
+  goto_functions.update();
+
+  return false;
+}
+

src/goto-instrument/model_argc_argv.h

@@ -0,0 +1,24 @@
+/*******************************************************************\
+
+Module: Initialize command line arguments
+
+Author: Michael Tautschnig
+
+Date: April 2016
+
+\*******************************************************************/
+
+#ifndef CPROVER_MODEL_ARGC_ARGV_H
+#define CPROVER_MODEL_ARGC_ARGV_H
+
+class goto_functionst;
+class message_handlert;
+class symbol_tablet;
+
+bool model_argc_argv(
+  symbol_tablet &symbol_table,
+  goto_functionst &goto_functions,
+  unsigned max_argc,
+  message_handlert &message_handler);
+
+#endif