[PATCH v2 1/2] Add attributes and methods to gdb.Inferior

[Tom Tromey <tromey@adacore.com>]

This adds two new attributes and three new methods to gdb.Inferior.

The attributes let Python code see the command-line arguments and the
name of "main".  Argument setting is also supported.

The methods let Python code manipulate the inferior's environment
variables.

Reviewed-By: Eli Zaretskii <eliz@gnu.org>
---
 gdb/NEWS                                 |  10 ++
 gdb/doc/python.texi                      |  44 ++++++++
 gdb/python/py-inferior.c                 | 169 +++++++++++++++++++++++++++++++
 gdb/testsuite/gdb.ada/py_range.exp       |   4 +
 gdb/testsuite/gdb.python/py-inferior.exp |  36 +++++++
 5 files changed, 263 insertions(+)

diff --git a/gdb/NEWS b/gdb/NEWS
index b82114d80b0..19bbb41c32f 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -192,6 +192,16 @@ info main
      - Changes are backwards compatible, the older API can still be
        used to disassemble instructions without styling.
 
+  ** gdb.Inferior now has a new "arguments" attribute.  This holds the
+     command-line arguments to the inferior, if known.
+
+  ** gdb.Inferior now has a new "main_name" attribute.  This holds the
+     name of the inferior's "main", if known.
+
+  ** gdb.Inferior now has new methods "clear_env", "set_env", and
+     "unset_env".  These can be used to modify the inferior's
+     environment before it is started.
+
 *** Changes in GDB 13
 
 * MI version 1 is deprecated, and will be removed in GDB 14.
diff --git a/gdb/doc/python.texi b/gdb/doc/python.texi
index 5d714ee1ca3..4bdd52466d0 100644
--- a/gdb/doc/python.texi
+++ b/gdb/doc/python.texi
@@ -3446,10 +3446,30 @@ Boolean signaling whether the inferior was created using `attach', or
 started by @value{GDBN} itself.
 @end defvar
 
+@defvar Inferior.main_name
+A string holding the name of this inferior's ``main'' function, if it
+can be determined.  If the name of main is not known, this is
+@code{None}.
+@end defvar
+
 @defvar Inferior.progspace
 The inferior's program space.  @xref{Progspaces In Python}.
 @end defvar
 
+@defvar Inferior.arguments
+The inferior's command line arguments, if known.  This corresponds to
+the @code{set args} and @code{show args} commands.  @xref{Arguments}.
+
+When accessed, the value is a string holding all the arguments.  The
+contents are quoted as they would be when passed to the shell.  If
+there are no arguments, the value is @code{None}.
+
+Either a string or a sequence of strings can be assigned to this
+attribute.  When a string is assigned, it is assumed to have any
+necessary quoting for the shell; when a sequence is assigned, the
+quoting is applied by @value{GDBN}.
+@end defvar
+
 A @code{gdb.Inferior} object has the following methods:
 
 @defun Inferior.is_valid ()
@@ -3517,6 +3537,30 @@ the same functionality, but use of @code{Inferior.thread_from_thread_handle}
 is deprecated.
 @end defun
 
+
+The environment that will be passed to the inferior can be changed
+from Python by using the following methods.  These methods only take
+effect when the inferior is started -- they will not affect an
+inferior that is already executing.
+
+@findex Inferior.clear_env
+@defun Inferior.clear_env ()
+Clear the current environment variables that will be passed to this
+inferior.
+@end defun
+
+@findex Inferior.set_env
+@defun Inferior.set_env (name, value)
+Set the environment variable @var{name} to have the indicated value.
+Both parameters must be strings.
+@end defun
+
+@findex Inferior.unset_env
+@defun Inferior.unset_env (name)
+Unset the environment variable @var{name}.  @var{name} must be a
+string.
+@end defun
+
 @node Events In Python
 @subsubsection Events In Python
 @cindex inferior events in Python
diff --git a/gdb/python/py-inferior.c b/gdb/python/py-inferior.c
index 982d0f803a0..8c4871dfa89 100644
--- a/gdb/python/py-inferior.c
+++ b/gdb/python/py-inferior.c
@@ -770,6 +770,162 @@ infpy_repr (PyObject *obj)
 			       inf->num, inf->pid);
 }
 
+/* Implement clear_env.  */
+
+static PyObject *
+infpy_clear_env (PyObject *obj)
+{
+  inferior_object *self = (inferior_object *) obj;
+
+  INFPY_REQUIRE_VALID (self);
+
+  self->inferior->environment.clear ();
+  Py_RETURN_NONE;
+}
+
+/* Implement set_env.  */
+
+static PyObject *
+infpy_set_env (PyObject *obj, PyObject *args, PyObject *kw)
+{
+  inferior_object *self = (inferior_object *) obj;
+  INFPY_REQUIRE_VALID (self);
+
+  const char *name, *val;
+  static const char *keywords[] = { "name", "value", nullptr };
+
+  if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "ss", keywords,
+					&name, &val))
+    return nullptr;
+
+  self->inferior->environment.set (name, val);
+  Py_RETURN_NONE;
+}
+
+/* Implement unset_env.  */
+
+static PyObject *
+infpy_unset_env (PyObject *obj, PyObject *args, PyObject *kw)
+{
+  inferior_object *self = (inferior_object *) obj;
+  INFPY_REQUIRE_VALID (self);
+
+  const char *name;
+  static const char *keywords[] = { "name", nullptr };
+  if (!gdb_PyArg_ParseTupleAndKeywords (args, kw, "s", keywords, &name))
+    return nullptr;
+
+  self->inferior->environment.unset (name);
+  Py_RETURN_NONE;
+}
+
+/* Getter for "arguments".  */
+
+static PyObject *
+infpy_get_args (PyObject *self, void *closure)
+{
+  inferior_object *inf = (inferior_object *) self;
+
+  INFPY_REQUIRE_VALID (inf);
+
+  const std::string &args = inf->inferior->args ();
+  if (args.empty ())
+    Py_RETURN_NONE;
+
+  return host_string_to_python_string (args.c_str ()).release ();
+}
+
+/* Setter for "arguments".  */
+
+static int
+infpy_set_args (PyObject *self, PyObject *value, void *closure)
+{
+  inferior_object *inf = (inferior_object *) self;
+
+  if (!inf->inferior)
+    {
+      PyErr_SetString (PyExc_RuntimeError, _("Inferior no longer exists."));
+      return -1;
+    }
+
+  if (value == nullptr)
+    {
+      PyErr_SetString (PyExc_TypeError,
+		       _("Cannot delete 'arguments' attribute."));
+      return -1;
+    }
+
+  if (gdbpy_is_string (value))
+    {
+      gdb::unique_xmalloc_ptr<char> str = python_string_to_host_string (value);
+      if (str == nullptr)
+	return -1;
+      inf->inferior->set_args (std::string (str.get ()));
+    }
+  else if (PySequence_Check (value))
+    {
+      std::vector<gdb::unique_xmalloc_ptr<char>> args;
+      Py_ssize_t len = PySequence_Size (value);
+      if (len == -1)
+	return -1;
+      for (Py_ssize_t i = 0; i < len; ++i)
+	{
+	  gdbpy_ref<> item (PySequence_ITEM (value, i));
+	  if (item == nullptr)
+	    return -1;
+	  gdb::unique_xmalloc_ptr<char> str
+	    = python_string_to_host_string (item.get ());
+	  if (str == nullptr)
+	    return -1;
+	  args.push_back (std::move (str));
+	}
+      std::vector<char *> argvec;
+      for (const auto &arg : args)
+	argvec.push_back (arg.get ());
+      gdb::array_view<char * const> view (argvec.data (), argvec.size ());
+      inf->inferior->set_args (view);
+    }
+  else
+    {
+      PyErr_SetString (PyExc_TypeError,
+		       _("string or sequence required for 'arguments'"));
+      return -1;
+    }
+  return 0;
+}
+
+/* Getter for "main_name".  */
+
+static PyObject *
+infpy_get_main_name (PyObject *self, void *closure)
+{
+  inferior_object *inf = (inferior_object *) self;
+
+  INFPY_REQUIRE_VALID (inf);
+
+  const char *name = nullptr;
+  try
+    {
+      /* This is unfortunate but the implementation of main_name can
+	 reach into memory.  */
+      scoped_restore_current_inferior restore_inferior;
+      set_current_inferior (inf->inferior);
+
+      scoped_restore_current_program_space restore_current_progspace;
+      set_current_program_space (inf->inferior->pspace);
+
+      name = main_name ();
+    }
+  catch (const gdb_exception &except)
+    {
+      /* We can just ignore this.  */
+    }
+
+  if (name == nullptr)
+    Py_RETURN_NONE;
+
+  return host_string_to_python_string (name).release ();
+}
 
 static void
 infpy_dealloc (PyObject *obj)
@@ -844,6 +1000,8 @@ GDBPY_INITIALIZE_FILE (gdbpy_initialize_inferior);
 
 static gdb_PyGetSetDef inferior_object_getset[] =
 {
+  { "arguments", infpy_get_args, infpy_set_args,
+    "Arguments to this program.", nullptr },
   { "num", infpy_get_num, NULL, "ID of inferior, as assigned by GDB.", NULL },
   { "connection", infpy_get_connection, NULL,
     "The gdb.TargetConnection for this inferior.", NULL },
@@ -854,6 +1012,8 @@ static gdb_PyGetSetDef inferior_object_getset[] =
   { "was_attached", infpy_get_was_attached, NULL,
     "True if the inferior was created using 'attach'.", NULL },
   { "progspace", infpy_get_progspace, NULL, "Program space of this inferior" },
+  { "main_name", infpy_get_main_name, nullptr,
+    "Name of 'main' function, if known.", nullptr },
   { NULL }
 };
 
@@ -889,6 +1049,15 @@ Return thread object corresponding to thread handle." },
   { "architecture", (PyCFunction) infpy_architecture, METH_NOARGS,
     "architecture () -> gdb.Architecture\n\
 Return architecture of this inferior." },
+  { "clear_env", (PyCFunction) infpy_clear_env, METH_NOARGS,
+    "clear_env () -> None\n\
+Clear environment of this inferior." },
+  { "set_env", (PyCFunction) infpy_set_env, METH_VARARGS | METH_KEYWORDS,
+    "set_env (name, value) -> None\n\
+Set an environment variable of this inferior." },
+  { "unset_env", (PyCFunction) infpy_unset_env, METH_VARARGS | METH_KEYWORDS,
+    "unset_env (name) -> None\n\
+Unset an environment of this inferior." },
   { NULL }
 };
 
diff --git a/gdb/testsuite/gdb.ada/py_range.exp b/gdb/testsuite/gdb.ada/py_range.exp
index 2972db21827..833493bad95 100644
--- a/gdb/testsuite/gdb.ada/py_range.exp
+++ b/gdb/testsuite/gdb.ada/py_range.exp
@@ -42,3 +42,7 @@ gdb_test "python print(gdb.parse_and_eval('si').type)" \
     "foo\\.small_integer" "print type"
 gdb_test "python print(gdb.parse_and_eval('si').type.name)" \
     "foo\\.small_integer" "print type name"
+
+gdb_test "python print(gdb.selected_inferior().main_name)" \
+    "_ada_foo" \
+    "print main name"
diff --git a/gdb/testsuite/gdb.python/py-inferior.exp b/gdb/testsuite/gdb.python/py-inferior.exp
index 424050a6166..58deece5d5f 100644
--- a/gdb/testsuite/gdb.python/py-inferior.exp
+++ b/gdb/testsuite/gdb.python/py-inferior.exp
@@ -342,3 +342,39 @@ with_test_prefix "architecture" {
 	"True" \
 	"inferior architecture matches frame architecture"
 }
+
+gdb_test "python print(gdb.selected_inferior().main_name)" \
+    "main" \
+    "print main name"
+
+gdb_test_no_output "set args x y z"
+gdb_test "python print(gdb.selected_inferior().arguments)" \
+    "x y z" \
+    "print arguments"
+
+gdb_test_no_output "python gdb.selected_inferior().arguments = 'a b c'" \
+    "set arguments from string"
+gdb_test "show args" \
+    [string_to_regexp "Argument list to give program being debugged when it is started is \"a b c\"."] \
+    "show args from string"
+
+gdb_test_no_output "python gdb.selected_inferior().arguments = \['a', 'b c'\]" \
+    "set arguments from list"
+gdb_test "show args" \
+    [string_to_regexp "Argument list to give program being debugged when it is started is \"a b\\ c\"."] \
+    "show args from list"
+
+gdb_test_no_output "python gdb.selected_inferior().clear_env()" \
+    "clear environment"
+gdb_test_no_output "show environment"
+
+gdb_test_no_output "python gdb.selected_inferior().set_env('DEI', 'value')" \
+    "set environment variable"
+gdb_test "show environment" \
+    "DEI=value" \
+    "examine environment variable"
+
+gdb_test_no_output "python gdb.selected_inferior().unset_env('DEI')" \
+    "unset environment variable"
+gdb_test_no_output "show environment" \
+    "environment is empty again"

-- 
2.40.0