Fix based on comments

Author: Petr Bauch

src/memory-analyzer/gdb_api.cpp

@@ -29,8 +29,11 @@ Author: Malte Mues <mail.mues@gmail.com>
 
 #include <goto-programs/goto_model.h>
 
+#include <util/prefix.h>
 #include <util/string_utils.h>
 
+#include <sys/wait.h>
+
 /// Create a gdb_apit object
 ///
 /// \param binary the binary to run with gdb
@@ -40,6 +43,31 @@ gdb_apit::gdb_apit(const char *binary, const bool log)
 {
 }
 
+/// Terminate the gdb process and close open streams (for reading from and
+/// writing to gdb)
+gdb_apit::~gdb_apit()
+{
+  PRECONDITION(
+    gdb_state == gdb_statet::CREATED || gdb_state == gdb_statet::STOPPED ||
+    gdb_state == gdb_statet::NOT_CREATED);
+
+  if(gdb_state == gdb_statet::NOT_CREATED)
+    return;
+
+  write_to_gdb("-gdb-exit");
+  // we cannot use most_recent_line_has_tag() here as it checks the last line
+  // before the next `(gdb) \n` prompt in the output; however when gdb exits no
+  // next prompt is printed
+  CHECK_RETURN(has_prefix(read_next_line(), "^exit"));
+
+  gdb_state = gdb_statet::NOT_CREATED;
+
+  fclose(command_stream);
+  fclose(response_stream);
+
+  wait(NULL);
+}
+
 /// Create a new gdb process for analysing the binary indicated by the member
 /// variable `binary`
 void gdb_apit::create_gdb_process()
@@ -82,10 +110,10 @@ void gdb_apit::create_gdb_process()
 
     dprintf(pipe_output[1], "binary name: %s\n", binary);
 
-    char *arg[] = {const_cast<char *>("gdb"),
-                   const_cast<char *>("--interpreter=mi"),
-                   const_cast<char *>(binary),
-                   NULL};
+    char *const arg[] = {const_cast<char *>("gdb"),
+                         const_cast<char *>("--interpreter=mi"),
+                         const_cast<char *>(binary),
+                         NULL};
 
     dprintf(pipe_output[1], "Loading gdb...\n");
     execvp("gdb", arg);
@@ -103,68 +131,50 @@ void gdb_apit::create_gdb_process()
     close(pipe_output[1]);
 
     // get stream for reading the gdb output
-    input_stream = fdopen(pipe_output[0], "r");
+    response_stream = fdopen(pipe_output[0], "r");
 
     // get stream for writing to gdb
-    output_stream = fdopen(pipe_input[1], "w");
+    command_stream = fdopen(pipe_input[1], "w");
 
-    CHECK_RETURN(most_recent_line_has_tag(R"(~"done)"));
+    bool has_done_tag = most_recent_line_has_tag(R"(~"done)");
+    CHECK_RETURN(has_done_tag);
 
     if(log)
     {
       // logs output to `gdb.txt` in the current directory, input is not logged
       // hence we log it to `command_log`
       write_to_gdb("-gdb-set logging on");
-      CHECK_RETURN(most_recent_line_has_tag("^done"));
+      check_command_accepted();
     }
 
     write_to_gdb("-gdb-set max-value-size unlimited");
-    CHECK_RETURN(most_recent_line_has_tag("^done"));
+    check_command_accepted();
   }
 }
 
-/// Terminate the gdb process and close open streams (for reading from and
-/// writing to gdb)
-void gdb_apit::terminate_gdb_process()
-{
-  PRECONDITION(
-    gdb_state == gdb_statet::CREATED || gdb_state == gdb_statet::STOPPED);
-
-  write_to_gdb("-gdb-exit");
-  // we cannot use most_recent_line_has_tag() here as it checks the last line
-  // before the next `(gdb) \n` prompt in the output; however when gdb exits no
-  // next prompt is printed
-  CHECK_RETURN(has_tag("^exit", read_next_line()));
-
-  gdb_state = gdb_statet::NOT_CREATED;
-
-  fclose(output_stream);
-  fclose(input_stream);
-}
-
 void gdb_apit::write_to_gdb(const std::string &command)
 {
   PRECONDITION(!command.empty());
-  PRECONDITION(command.back() != '\n');
+  PRECONDITION(command.find('\n') == std::string::npos);
 
   std::string line(command);
   line += '\n';
 
   if(log)
   {
-    command_log.push_back(command);
+    command_log.push_front(command);
   }
 
-  if(fputs(line.c_str(), output_stream) == EOF)
+  if(fputs(line.c_str(), command_stream) == EOF)
   {
     throw gdb_interaction_exceptiont("could not write a command to gdb");
   }
 
-  fflush(output_stream);
+  fflush(command_stream);
 }
 
 /// Return the vector of commands that have been written to gdb so far
-const std::vector<std::string> &gdb_apit::get_command_log()
+const gdb_apit::commandst &gdb_apit::get_command_log()
 {
   PRECONDITION(log);
   return command_log;
@@ -179,17 +189,17 @@ std::string gdb_apit::read_next_line()
     const size_t buf_size = 1024;
     char buf[buf_size]; // NOLINT(runtime/arrays)
 
-    const char *c = fgets(buf, buf_size, input_stream);
+    const char *c = fgets(buf, buf_size, response_stream);
 
     if(c == NULL)
     {
-      if(ferror(input_stream))
+      if(ferror(response_stream))
       {
         throw gdb_interaction_exceptiont("error reading from gdb");
       }
 
       INVARIANT(
-        feof(input_stream),
+        feof(response_stream),
         "EOF must have been reached when the error indicator on the stream "
         "is not set and fgets returned NULL");
       INVARIANT(
@@ -227,7 +237,7 @@ gdb_apit::gdb_output_recordt
 gdb_apit::get_most_recent_record(const std::string &tag, const bool must_exist)
 {
   std::string line = read_most_recent_line();
-  const bool b = has_tag(tag, line);
+  const bool b = has_prefix(line, tag);
 
   if(must_exist)
   {
@@ -243,15 +253,10 @@ gdb_apit::get_most_recent_record(const std::string &tag, const bool must_exist)
   return parse_gdb_output_record(record);
 }
 
-bool gdb_apit::has_tag(const std::string &tag, const std::string &line)
-{
-  return line.compare(0, tag.length(), tag) == 0;
-}
-
 bool gdb_apit::most_recent_line_has_tag(const std::string &tag)
 {
   const std::string line = read_most_recent_line();
-  return has_tag(tag, line);
+  return has_prefix(line, tag);
 }
 
 /// Run gdb with the given core file
@@ -265,7 +270,7 @@ void gdb_apit::run_gdb_from_core(const std::string &corefile)
   const std::string command = "core " + corefile;
 
   write_to_gdb(command);
-  CHECK_RETURN(most_recent_line_has_tag("^done"));
+  check_command_accepted();
 
   gdb_state = gdb_statet::STOPPED;
 }
@@ -282,7 +287,7 @@ bool gdb_apit::run_gdb_to_breakpoint(const std::string &breakpoint)
   command += " " + breakpoint;
 
   write_to_gdb(command);
-  if(!most_recent_line_has_tag("^done"))
+  if(!was_command_accepted())
   {
     throw gdb_interaction_exceptiont("could not set breakpoint");
   }
@@ -315,27 +320,24 @@ bool gdb_apit::run_gdb_to_breakpoint(const std::string &breakpoint)
       "gdb stopped for unhandled reason `" + reason + "`");
   }
 
-  // not reached
-  return true;
+  UNREACHABLE;
 }
 
 std::string gdb_apit::eval_expr(const std::string &expr)
 {
   write_to_gdb("-var-create tmp * " + expr);
 
-  if(!most_recent_line_has_tag("^done"))
+  if(!was_command_accepted())
   {
     throw gdb_interaction_exceptiont(
-      "could not create variable for "
-      "expression `" +
-      expr + "`");
+      "could not create variable for expression `" + expr + "`");
   }
 
   write_to_gdb("-var-evaluate-expression tmp");
   gdb_output_recordt record = get_most_recent_record("^done", true);
 
   write_to_gdb("-var-delete tmp");
-  CHECK_RETURN(most_recent_line_has_tag("^done"));
+  check_command_accepted();
 
   const auto it = record.find("value");
   CHECK_RETURN(it != record.end());
@@ -381,8 +383,7 @@ std::string gdb_apit::get_memory(const std::string &expr)
       "` is not a memory address or has unrecognised format");
   }
 
-  // not reached
-  return "";
+  UNREACHABLE;
 }
 
 /// Get value of the given value expression
@@ -432,7 +433,7 @@ gdb_apit::parse_gdb_output_record(const std::string &s)
 
   gdb_output_recordt result;
 
-  unsigned depth = 0;
+  std::size_t depth = 0;
   std::string::size_type start = 0;
 
   const std::string::size_type n = s.length();
@@ -488,4 +489,15 @@ gdb_apit::parse_gdb_output_record(const std::string &s)
   return result;
 }
 
+bool gdb_apit::was_command_accepted()
+{
+  return most_recent_line_has_tag("^done");
+}
+
+void gdb_apit::check_command_accepted()
+{
+  bool was_accepted = was_command_accepted();
+  CHECK_RETURN(was_accepted);
+}
+
 #endif

src/memory-analyzer/gdb_api.h

@@ -29,13 +29,17 @@ Author: Malte Mues <mail.mues@gmail.com>
 #include <unistd.h>
 
 #include <exception>
+#include <forward_list>
 
 #include <util/exception_utils.h>
 
 class gdb_apit
 {
 public:
+  using commandst = std::forward_list<std::string>;
+
   explicit gdb_apit(const char *binary, const bool log = false);
+  ~gdb_apit();
 
   void create_gdb_process();
   void terminate_gdb_process();
@@ -46,22 +50,22 @@ class gdb_apit
   std::string get_value(const std::string &expr);
   std::string get_memory(const std::string &expr);
 
-  const std::vector<std::string> &get_command_log();
+  const commandst &get_command_log();
 
 protected:
   const char *binary;
 
-  FILE *input_stream;
-  FILE *output_stream;
+  FILE *response_stream;
+  FILE *command_stream;
 
   const bool log;
-  std::vector<std::string> command_log;
+  commandst command_log;
 
   enum class gdb_statet
   {
     NOT_CREATED,
     CREATED,
-    STOPPED
+    STOPPED // valid state, reached e.g. after breakpoint was hit
   };
 
   gdb_statet gdb_state;
@@ -79,9 +83,9 @@ class gdb_apit
   gdb_output_recordt
   get_most_recent_record(const std::string &tag, const bool must_exist = false);
 
-  static bool has_tag(const std::string &tag, const std::string &line);
-
   bool most_recent_line_has_tag(const std::string &tag);
+  bool was_command_accepted();
+  void check_command_accepted();
 };
 
 class gdb_interaction_exceptiont : public cprover_exception_baset

src/memory-analyzer/module_dependencies.txt

@@ -1,2 +1,3 @@
 goto-programs
 util
+sys

unit/memory-analyzer/gdb_api.cpp

@@ -60,9 +60,7 @@ void gdb_api_internals_test()
   {
     gdb_api_testt gdb_api("test");
 
-    gdb_api_testt::gdb_output_recordt gor;
-
-    gor = gdb_api.parse_gdb_output_record(
+    gdb_api_testt::gdb_output_recordt gor = gdb_api.parse_gdb_output_record(
       "a = \"1\", b = \"2\", c = {1, 2}, d = [3, 4], e=\"0x0\"");
 
     REQUIRE(gor["a"] == "1");
@@ -77,11 +75,9 @@ void gdb_api_internals_test()
     gdb_api_testt gdb_api("test");
 
     FILE *f = fopen("memory-analyzer/input.txt", "r");
-    gdb_api.input_stream = f;
-
-    std::string line;
+    gdb_api.response_stream = f;
 
-    line = gdb_api.read_next_line();
+    std::string line = gdb_api.read_next_line();
     REQUIRE(line == "abc\n");
 
     line = gdb_api.read_next_line();
@@ -98,10 +94,8 @@ void gdb_api_internals_test()
     gdb_api.create_gdb_process();
 
     // check input and output streams
-    REQUIRE(!ferror(gdb_api.input_stream));
-    REQUIRE(!ferror(gdb_api.output_stream));
-
-    gdb_api.terminate_gdb_process();
+    REQUIRE(!ferror(gdb_api.response_stream));
+    REQUIRE(!ferror(gdb_api.command_stream));
   }
 }
 
@@ -127,8 +121,6 @@ TEST_CASE("gdb api test", "[core][memory-analyzer]")
     {
       const bool r = gdb_api.run_gdb_to_breakpoint("checkpoint");
       REQUIRE(r);
-
-      gdb_api.terminate_gdb_process();
     }
     catch(const gdb_interaction_exceptiont &e)
     {
@@ -155,8 +147,6 @@ TEST_CASE("gdb api test", "[core][memory-analyzer]")
 
       std::cerr << "=== gdb log end ===\n";
 
-      gdb_api.terminate_gdb_process();
-
       return;
     }
   }
@@ -203,6 +193,5 @@ TEST_CASE("gdb api test", "[core][memory-analyzer]")
     }
   }
 
-  gdb_api.terminate_gdb_process();
 #endif
 }