[PATCH v2 4/5] Implement "set cwd" command

[Sergio Durigan Junior <sergiodj at redhat dot com>]

This is the actual implementation of the "set/show cwd" commands.  The
way they work is:

- If the user sets the inferior's cwd by using "set cwd", then this
  directory is saved into current_inferior ()->cwd and is used when
  the inferior is started (see below).

- If the user doesn't set the inferior's cwd by using "set cwd", but
  rather use the "cd" command as before, the this directory is
  inherited by the inferior because GDB will have chdir'd into it.

The way the directory is changed before the inferior execution is by
calling "gdb_chdir" after the call to fork/vfork on "fork_inferior",
but before the actual execution.  This way, we'll make sure that GDB's
cwd is not affected by the user set cwd.

gdb/ChangeLog:
yyyy-mm-dd  Sergio Durigan Junior  <sergiodj@redhat.com>

	* NEWS (New commands): Mention "set/show cwd".
	* cli/cli-cmds.c (_initialize_cli_cmds): Mention "set cwd" on
	"cd" command's help text.
	* common/common-inferior.h (get_inferior_cwd): New prototype.
	* infcmd.c: Include "gdb_chdir.h" and "readline/tilde.h".
	(inferior_cwd_scratch): New global variable.
	(set_inferior_cwd): New function.
	(get_inferior_cwd): Likewise.
	(set_cwd_command): Likewise.
	(show_cwd_command): Likewise.
	(_initialize_infcmd): Add "set/show cwd" commands.
	* inferior.h (class inferior) <cwd>: New field.
	* nat/fork-inferior.c: Include "gdb_chdir.h".
	(fork_inferior): Change inferior's cwd before its execution.
	* windows-nat.c (windows_create_inferior): Pass inferior's cwd
	to CreateProcess.

gdb/gdbserver/ChangeLog:
yyyy-mm-dd  Sergio Durigan Junior  <sergiodj@redhat.com>

	* inferiors.c (get_inferior_cwd): New function.
	* inferiors.h (struct process_info) <cwd>: New field.

gdb/doc/ChangeLog:
yyyy-mm-dd  Sergio Durigan Junior  <sergiodj@redhat.com>

	* gdb.texinfo (Starting your Program) <The working directory.>:
	Mention new "set cwd" command.
	(Working Directory) <Your Program's Working Directory>:
	Rephrase to explain that "set cwd" exists and is the default
	way to change the inferior's cwd.

gdb/testsuite/ChangeLog:
yyyy-mm-dd  Sergio Durigan Junior  <sergiodj@redhat.com>

	* gdb.base/set-cwd.c: New file.
	* gdb.base/set-cwd.exp: Likewise.
---
 gdb/NEWS                           |  3 ++
 gdb/cli/cli-cmds.c                 |  6 +--
 gdb/common/common-inferior.h       |  4 ++
 gdb/doc/gdb.texinfo                | 34 ++++++++++----
 gdb/gdbserver/inferiors.c          | 11 +++++
 gdb/infcmd.c                       | 75 +++++++++++++++++++++++++++++++
 gdb/inferior.h                     |  4 ++
 gdb/nat/fork-inferior.c            | 17 +++++++
 gdb/testsuite/gdb.base/set-cwd.c   | 29 ++++++++++++
 gdb/testsuite/gdb.base/set-cwd.exp | 90 ++++++++++++++++++++++++++++++++++++++
 gdb/windows-nat.c                  |  5 ++-
 11 files changed, 265 insertions(+), 13 deletions(-)
 create mode 100644 gdb/testsuite/gdb.base/set-cwd.c
 create mode 100644 gdb/testsuite/gdb.base/set-cwd.exp

diff --git a/gdb/NEWS b/gdb/NEWS
index 3244f7effe..0dcfcc98af 100644
--- a/gdb/NEWS
+++ b/gdb/NEWS
@@ -64,6 +64,9 @@ QStartupWithShell
 
 * New commands
 
+set|show cwd
+  Set and show the current working directory for the inferior.
+
 set|show compile-gcc
   Set and show compilation command used for compiling and injecting code
   with the 'compile' commands.
diff --git a/gdb/cli/cli-cmds.c b/gdb/cli/cli-cmds.c
index 653dd56a64..f086f10aea 100644
--- a/gdb/cli/cli-cmds.c
+++ b/gdb/cli/cli-cmds.c
@@ -1716,9 +1716,9 @@ The commands below can be used to select other frames by number or address."),
 Print working directory.  This is used for your program as well."));
 
   c = add_cmd ("cd", class_files, cd_command, _("\
-Set working directory to DIR for debugger and program being debugged.\n\
-The change does not take effect for the program being debugged\n\
-until the next time it is started."), &cmdlist);
+Set working directory to DIR for debugger.\n\
+In order to change the inferior's current working directory, the recommended\n\
+way is to use the \"set cwd\" command."), &cmdlist);
   set_cmd_completer (c, filename_completer);
 
   add_com ("echo", class_support, echo_command, _("\
diff --git a/gdb/common/common-inferior.h b/gdb/common/common-inferior.h
index 87c13009ed..515a8c0f4e 100644
--- a/gdb/common/common-inferior.h
+++ b/gdb/common/common-inferior.h
@@ -30,4 +30,8 @@ extern const char *get_exec_wrapper ();
    otherwise return 0 in that case.  */
 extern char *get_exec_file (int err);
 
+/* Return the inferior's current working directory.  If nothing has
+   been set, then return NULL.  */
+extern const char *get_inferior_cwd ();
+
 #endif /* ! COMMON_INFERIOR_H */
diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
index af5fe6f46c..c513a49c26 100644
--- a/gdb/doc/gdb.texinfo
+++ b/gdb/doc/gdb.texinfo
@@ -2057,8 +2057,9 @@ environment} to change parts of the environment that affect
 your program.  @xref{Environment, ,Your Program's Environment}.
 
 @item The @emph{working directory.}
-Your program inherits its working directory from @value{GDBN}.  You can set
-the @value{GDBN} working directory with the @code{cd} command in @value{GDBN}.
+You can set your program's working directory with the command
+@code{set cwd}.  If you do not set any working directory with this
+command, your program will inherit @value{GDBN}'s working directory.
 @xref{Working Directory, ,Your Program's Working Directory}.
 
 @item The @emph{standard input and output.}
@@ -2424,19 +2425,36 @@ variables to files that are only run when you sign on, such as
 @section Your Program's Working Directory
 
 @cindex working directory (of your program)
-Each time you start your program with @code{run}, it inherits its
-working directory from the current working directory of @value{GDBN}.
-The @value{GDBN} working directory is initially whatever it inherited
-from its parent process (typically the shell), but you can specify a new
-working directory in @value{GDBN} with the @code{cd} command.
+Each time you start your program with @code{run}, the inferior will be
+initialized with the current working directory specified by the
+@code{set cwd} command.  If no directory has been specified by this
+command, then the inferior will inherit @value{GDBN}'s current working
+directory as its working directory.
+
+You can also change @value{GDBN}'s current working directory by using
+the @code{cd} command.
 
 The @value{GDBN} working directory also serves as a default for the commands
 that specify files for @value{GDBN} to operate on.  @xref{Files, ,Commands to
 Specify Files}.
 
 @table @code
+@kindex set cwd
+@cindex change inferior's working directory
+@item set cwd @r{[}@var{directory}@r{]}
+Set the inferior's working directory to @var{directory}.  If not
+given, @var{directory} uses @file{'~'}.  This has no effect on
+@value{GDBN}'s working directory.
+
+@kindex show cwd
+@cindex show inferior's working directory
+@item show cwd
+Show the inferior's working directory.  If no directory has been
+specified by @code{set cwd}, then the default inferior's working
+directory is the same as @value{GDBN}'s working directory.
+
 @kindex cd
-@cindex change working directory
+@cindex change @value{GDBN}'s working directory
 @item cd @r{[}@var{directory}@r{]}
 Set the @value{GDBN} working directory to @var{directory}.  If not
 given, @var{directory} uses @file{'~'}.
diff --git a/gdb/gdbserver/inferiors.c b/gdb/gdbserver/inferiors.c
index 72f0412757..e78ad4faf1 100644
--- a/gdb/gdbserver/inferiors.c
+++ b/gdb/gdbserver/inferiors.c
@@ -29,6 +29,9 @@ struct thread_info *current_thread;
 
 #define get_thread(inf) ((struct thread_info *)(inf))
 
+/* The current working directory used to start the inferior.  */
+static const char *current_inferior_cwd = NULL;
+
 void
 add_inferior_to_list (struct inferior_list *list,
 		      struct inferior_list_entry *new_inferior)
@@ -445,3 +448,11 @@ switch_to_thread (ptid_t ptid)
   if (!ptid_equal (ptid, minus_one_ptid))
     current_thread = find_thread_ptid (ptid);
 }
+
+/* See common/common-inferior.h.  */
+
+const char *
+get_inferior_cwd ()
+{
+  return current_inferior_cwd;
+}
diff --git a/gdb/infcmd.c b/gdb/infcmd.c
index 25cf025426..178a3ca15f 100644
--- a/gdb/infcmd.c
+++ b/gdb/infcmd.c
@@ -59,6 +59,8 @@
 #include "top.h"
 #include "interps.h"
 #include "common/gdb_optional.h"
+#include "gdb_chdir.h"
+#include "readline/tilde.h"
 
 /* Local functions: */
 
@@ -111,6 +113,10 @@ static void run_command (char *, int);
 
 static char *inferior_args_scratch;
 
+/* Scratch area where the new cwd will be stored by 'set cwd'.  */
+
+static char *inferior_cwd_scratch;
+
 /* Scratch area where 'set inferior-tty' will store user-provided value.
    We'll immediate copy it into per-inferior storage.  */
 
@@ -246,6 +252,56 @@ show_args_command (struct ui_file *file, int from_tty,
   deprecated_show_value_hack (file, from_tty, c, get_inferior_args ());
 }
 
+/* Set the inferior current working directory.  This directory will be
+   entered by GDB before executing the inferior.  */
+
+static void
+set_inferior_cwd (const char *cwd)
+{
+  struct inferior *inf = current_inferior ();
+
+  gdb_assert (inf != NULL);
+  xfree ((void *) inf->cwd);
+  inf->cwd = tilde_expand (*cwd != '\0' ? cwd : "~");
+}
+
+/* See common/common-inferior.h.  */
+
+const char *
+get_inferior_cwd ()
+{
+  return current_inferior ()->cwd;
+}
+
+/* Handle the 'set cwd' command.  */
+
+static void
+set_cwd_command (char *args, int from_tty, struct cmd_list_element *c)
+{
+  set_inferior_cwd (inferior_cwd_scratch);
+}
+
+/* Handle the 'show cwd' command.  */
+
+static void
+show_cwd_command (struct ui_file *file, int from_tty,
+		  struct cmd_list_element *c, const char *value)
+{
+  const char *cwd = get_inferior_cwd ();
+
+  if (cwd == NULL)
+    {
+      /* To maintain backwards compatibility, we use
+	 'current_directory' here, which is set by the "cd"
+	 command.  */
+      cwd = current_directory;
+    }
+
+  fprintf_filtered (gdb_stdout,
+		    _("Current working directory that will be used "
+		      "when starting the inferior is \"%s\".\n"), cwd);
+}
+
 
 /* Compute command-line string given argument vector.  This does the
    same shell processing as fork_inferior.  */
@@ -3214,6 +3270,25 @@ Follow this command with any number of args, to be passed to the program."),
   gdb_assert (c != NULL);
   set_cmd_completer (c, filename_completer);
 
+  cmd_name = "cwd";
+  add_setshow_string_noescape_cmd (cmd_name, class_run,
+				   &inferior_cwd_scratch, _("\
+Set the current working directory to be used when the inferior is started.\n\
+Changing this setting does not have any effect on inferiors that are\n\
+already running."),
+				   _("\
+Show the current working directory that is used when the inferior is started."),
+				   _("\
+Use this command to change the current working directory that will be used\n\
+when the inferior is started.  This setting does not affect GDB's current\n\
+working directory."),
+				   set_cwd_command,
+				   show_cwd_command,
+				   &setlist, &showlist);
+  c = lookup_cmd (&cmd_name, setlist, "", -1, 1);
+  gdb_assert (c != NULL);
+  set_cmd_completer (c, filename_completer);
+
   c = add_cmd ("environment", no_class, environment_info, _("\
 The environment to give the program, or one variable's value.\n\
 With an argument VAR, prints the value of environment variable VAR to\n\
diff --git a/gdb/inferior.h b/gdb/inferior.h
index 6d020f73c4..bcd1e54a03 100644
--- a/gdb/inferior.h
+++ b/gdb/inferior.h
@@ -355,6 +355,10 @@ public:
      should never be freed.  */
   char **argv = NULL;
 
+  /* The current working directory that will be used when starting
+     this inferior.  */
+  const char *cwd = NULL;
+
   /* The name of terminal device to use for I/O.  */
   char *terminal = NULL;
 
diff --git a/gdb/nat/fork-inferior.c b/gdb/nat/fork-inferior.c
index 0913409e6d..6ff0c2d216 100644
--- a/gdb/nat/fork-inferior.c
+++ b/gdb/nat/fork-inferior.c
@@ -25,6 +25,7 @@
 #include "common-inferior.h"
 #include "common-gdbthread.h"
 #include "signals-state-save-restore.h"
+#include "gdb_chdir.h"
 #include <vector>
 
 extern char **environ;
@@ -376,6 +377,22 @@ fork_inferior (const char *exec_file_arg, const std::string &allargs,
 	 UIs.  */
       close_most_fds ();
 
+      const char *cwd = get_inferior_cwd ();
+
+      if (cwd != NULL)
+	{
+	  TRY
+	    {
+	      gdb_chdir (cwd);
+	    }
+	  CATCH (ex, RETURN_MASK_ERROR)
+	    {
+	      warning ("%s", ex.message);
+	      _exit (0177);
+	    }
+	  END_CATCH
+	}
+
       if (debug_fork)
 	sleep (debug_fork);
 
diff --git a/gdb/testsuite/gdb.base/set-cwd.c b/gdb/testsuite/gdb.base/set-cwd.c
new file mode 100644
index 0000000000..488fc4e4e3
--- /dev/null
+++ b/gdb/testsuite/gdb.base/set-cwd.c
@@ -0,0 +1,29 @@
+/* This testcase is part of GDB, the GNU debugger.
+
+   Copyright 2017 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 <stdio.h>
+#include <unistd.h>
+
+int
+main (int argc, char *argv[])
+{
+  char dir[BUFSIZ];
+
+  getcwd (dir, BUFSIZ);
+
+  return 0; /* break-here */
+}
diff --git a/gdb/testsuite/gdb.base/set-cwd.exp b/gdb/testsuite/gdb.base/set-cwd.exp
new file mode 100644
index 0000000000..3a6ffd3862
--- /dev/null
+++ b/gdb/testsuite/gdb.base/set-cwd.exp
@@ -0,0 +1,90 @@
+# This testcase is part of GDB, the GNU debugger.
+
+# Copyright 2017 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/>.
+
+if { ![isnative] || [is_remote target] || [is_remote host]
+     || [target_info gdb_protocol] == "extended-remote" } then {
+    untested "not implemented on gdbserver"
+    return
+}
+
+standard_testfile
+
+if { [prepare_for_testing "failed to prepare" $testfile $srcfile debug] } {
+    return -1
+}
+
+# Test that tilde expansion works fine.
+
+proc test_tilde_expansion { } {
+    if { [info exists ::env(HOME)] } {
+	with_test_prefix "test tilde expansion" {
+	    set home $::env(HOME)
+
+	    gdb_test_no_output "set cwd ~/test" "set cwd to ~/test dir"
+
+	    gdb_test "show cwd" \
+		"Current working directory that will be used when starting the inferior is \"${home}/test\"\." \
+		"show cwd shows expanded tilde"
+	}
+    }
+}
+
+# Test that when we "set cwd" the inferior will be started under the
+# correct working directory and GDB will not be affected by this.
+
+proc test_cd_into_dir { } {
+    global decimal gdb_prompt
+
+    with_test_prefix "test cd into temp dir" {
+	gdb_test_multiple "pwd" "pwd before run" {
+	    -re "Working directory \(.*\)\.\r\n$gdb_prompt $" {
+		set gdb_cwd_before_run $expect_out(1,string)
+	    }
+	}
+
+	set tmpdir [standard_output_file ""]
+
+	gdb_test_no_output "set cwd $tmpdir" "set cwd to temp dir"
+
+	if { ![runto_main] } {
+	    untested "could not run to main"
+	    return -1
+	}
+
+	gdb_breakpoint [gdb_get_line_number "break-here"]
+	gdb_continue_to_breakpoint "break-here" ".* break-here .*"
+
+	gdb_test "print dir" "\\\$$decimal = \"$tmpdir\", .*" \
+	    "inferior cwd is correctly set"
+
+	gdb_test_multiple "pwd" "pwd after run" {
+	    -re "Working directory \(.*\)\.\r\n$gdb_prompt $" {
+		set gdb_cwd_after_run $expect_out(1,string)
+	    }
+	}
+
+	set test "GDB cwd is unchanged after running inferior"
+	if { [string equal $gdb_cwd_before_run $gdb_cwd_after_run] } {
+	    pass $test
+	} else {
+	    fail $test
+	}
+    }
+}
+
+test_cd_into_dir
+test_tilde_expansion
diff --git a/gdb/windows-nat.c b/gdb/windows-nat.c
index ab5582d46c..9732a2d175 100644
--- a/gdb/windows-nat.c
+++ b/gdb/windows-nat.c
@@ -2461,6 +2461,7 @@ windows_create_inferior (struct target_ops *ops, const char *exec_file,
   BOOL ret;
   DWORD flags = 0;
   const char *inferior_io_terminal = get_inferior_io_terminal ();
+  const char *inferior_cwd = get_inferior_cwd ();
 
   if (!exec_file)
     error (_("No executable specified, use `target exec'."));
@@ -2574,7 +2575,7 @@ windows_create_inferior (struct target_ops *ops, const char *exec_file,
 		       TRUE,	/* inherit handles */
 		       flags,	/* start flags */
 		       w32_env,	/* environment */
-		       NULL,	/* current directory */
+		       inferior_cwd,	/* current directory */
 		       &si,
 		       &pi);
   if (w32_env)
@@ -2697,7 +2698,7 @@ windows_create_inferior (struct target_ops *ops, const char *exec_file,
 			TRUE,	/* inherit handles */
 			flags,	/* start flags */
 			w32env,	/* environment */
-			NULL,	/* current directory */
+			inferior_cwd,	/* current directory */
 			&si,
 			&pi);
   if (tty != INVALID_HANDLE_VALUE)
-- 
2.13.3