gdbsupport: rename source files to .cc

This patch renames the .c source files in gdbsupport to .cc.

In the gdb directory, there is an argument against renaming the source
files, which is that it makes using some git commands more difficult to
do archeology.  Some commands have some kind of "follow" option that
makes git try to follow renames, but it doesn't work in all situations.

Given that we have just moved the gdbsupport directory, that argument
doesn't hold for source files in that directory.  I therefore suggest
renaming them to .cc, so that they are automatically recognized as C++
by various tools and editors.

The original motivation behind this is that when building gdbsupport
with clang, I get:

      CC       agent.o
    clang: error: treating 'c' input as 'c++' when in C++ mode, this behavior is deprecated [-Werror,-Wdeprecated]

In the gdb/ directory, we make clang happy by passing "-x c++".  We
could do this in gdbsupport too, but I think that renaming the files is
a better long-term solution.

gdbserver still does its own build of gdbsupport, so a few changes in
its Makefile are necessary.

gdbsupport/ChangeLog:

	* Makefile.am: Rename source files from .c to .cc.
	(CC, CFLAGS): Don't override.
	(AM_CFLAGS): Rename to ...
	(AM_CXXFLAGS): ... this.
	* Makefile.in: Re-generate.
	* %.c: Rename to %.cc.

gdbserver/ChangeLog:

	* Makefile.in: Rename gdbsupport source files from .c to .cc.

1 files changed, 183 insertions, 0 deletions

diff --git a/gdbsupport/environ.cc b/gdbsupport/environ.cc
new file mode 100644
index 00000000000..32434ee0b74
--- /dev/null
+++ b/gdbsupport/environ.cc
@@ -0,0 +1,183 @@
+/* environ.c -- library for manipulating environments for GNU.
+
+   Copyright (C) 1986-2020 Free Software Foundation, Inc.
+
+   This program is free software; you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
+
+#include "common-defs.h"
+#include "environ.h"
+#include <algorithm>
+#include <utility>
+
+/* See gdbsupport/environ.h.  */
+
+gdb_environ &
+gdb_environ::operator= (gdb_environ &&e)
+{
+  /* Are we self-moving?  */
+  if (&e == this)
+    return *this;
+
+  m_environ_vector = std::move (e.m_environ_vector);
+  m_user_set_env = std::move (e.m_user_set_env);
+  m_user_unset_env = std::move (e.m_user_unset_env);
+  e.m_environ_vector.clear ();
+  e.m_environ_vector.push_back (NULL);
+  e.m_user_set_env.clear ();
+  e.m_user_unset_env.clear ();
+  return *this;
+}
+
+/* See gdbsupport/environ.h.  */
+
+gdb_environ gdb_environ::from_host_environ ()
+{
+  extern char **environ;
+  gdb_environ e;
+
+  if (environ == NULL)
+    return e;
+
+  for (int i = 0; environ[i] != NULL; ++i)
+    {
+      /* Make sure we add the element before the last (NULL).  */
+      e.m_environ_vector.insert (e.m_environ_vector.end () - 1,
+				 xstrdup (environ[i]));
+    }
+
+  return e;
+}
+
+/* See gdbsupport/environ.h.  */
+
+void
+gdb_environ::clear ()
+{
+  for (char *v : m_environ_vector)
+    xfree (v);
+  m_environ_vector.clear ();
+  /* Always add the NULL element.  */
+  m_environ_vector.push_back (NULL);
+  m_user_set_env.clear ();
+  m_user_unset_env.clear ();
+}
+
+/* Helper function to check if STRING contains an environment variable
+   assignment of VAR, i.e., if STRING starts with 'VAR='.  Return true
+   if it contains, false otherwise.  */
+
+static bool
+match_var_in_string (const char *string, const char *var, size_t var_len)
+{
+  if (strncmp (string, var, var_len) == 0 && string[var_len] == '=')
+    return true;
+
+  return false;
+}
+
+/* See gdbsupport/environ.h.  */
+
+const char *
+gdb_environ::get (const char *var) const
+{
+  size_t len = strlen (var);
+
+  for (char *el : m_environ_vector)
+    if (el != NULL && match_var_in_string (el, var, len))
+      return &el[len + 1];
+
+  return NULL;
+}
+
+/* See gdbsupport/environ.h.  */
+
+void
+gdb_environ::set (const char *var, const char *value)
+{
+  char *fullvar = concat (var, "=", value, (char *) NULL);
+
+  /* We have to unset the variable in the vector if it exists.  */
+  unset (var, false);
+
+  /* Insert the element before the last one, which is always NULL.  */
+  m_environ_vector.insert (m_environ_vector.end () - 1, fullvar);
+
+  /* Mark this environment variable as having been set by the user.
+     This will be useful when we deal with setting environment
+     variables on the remote target.  */
+  m_user_set_env.insert (std::string (fullvar));
+
+  /* If this environment variable is marked as unset by the user, then
+     remove it from the list, because now the user wants to set
+     it.  */
+  m_user_unset_env.erase (std::string (var));
+}
+
+/* See gdbsupport/environ.h.  */
+
+void
+gdb_environ::unset (const char *var, bool update_unset_list)
+{
+  size_t len = strlen (var);
+  std::vector<char *>::iterator it_env;
+
+  /* We iterate until '.end () - 1' because the last element is
+     always NULL.  */
+  for (it_env = m_environ_vector.begin ();
+       it_env != m_environ_vector.end () - 1;
+       ++it_env)
+    if (match_var_in_string (*it_env, var, len))
+      break;
+
+  if (it_env != m_environ_vector.end () - 1)
+    {
+      m_user_set_env.erase (std::string (*it_env));
+      xfree (*it_env);
+
+      m_environ_vector.erase (it_env);
+    }
+
+  if (update_unset_list)
+    m_user_unset_env.insert (std::string (var));
+}
+
+/* See gdbsupport/environ.h.  */
+
+void
+gdb_environ::unset (const char *var)
+{
+  unset (var, true);
+}
+
+/* See gdbsupport/environ.h.  */
+
+char **
+gdb_environ::envp () const
+{
+  return const_cast<char **> (&m_environ_vector[0]);
+}
+
+/* See gdbsupport/environ.h.  */
+
+const std::set<std::string> &
+gdb_environ::user_set_env () const
+{
+  return m_user_set_env;
+}
+
+const std::set<std::string> &
+gdb_environ::user_unset_env () const
+{
+  return m_user_unset_env;
+}