Use construct_inferior_arguments which handles special chars

Use the construct_inferior_arguments function instead of
stringify_argv to construct a string from the program
arguments in those places where that one is then passed
to fork_inferior (linux-low, lyn-low), since
construct_inferior_arguments properly takes care of
special characters, while stringify_argv does not.
Using construct_inferior_arguments seems "natural", since its
documentation also mentions that it "does the
same shell processing as fork_inferior".

Since construct_inferior_args has been extended to do
proper quoting for Windows shells in commit
5d60742e2d
("Fix quoting of special characters for the MinGW build.",
2012-06-12), use it for the Windows case as well.
(I could not test that case myself, though.)

Adapt handling of empty args in function 'handle_v_run'
in gdbserver/server.cc to just insert an empty string
for an empty arg, since that one is now properly handled
in 'construct_inferior_arguments' already (and inserting
a "''" string in 'handle_v_run' would otherwise
cause that one to be treated as a string literally
containing two quote characters, which
'construct_inferior_args' would preserve by adding
extra escaping).

This makes gdbserver properly handle program args containing special
characters (like spaces), e.g. (example from PR25893)

  $ gdbserver localhost:50505 myprogram "hello world"

now properly handles "hello world" as a single arg, not two separate
ones ("hello", "world").

gdbserver/ChangeLog:

	PR gdbserver/25893
	* linux-low.cc (linux_process_target::create_inferior),
	lynx-low.cc (lynx_process_target::create_inferior),
	win32-low.cc (win32_process_target::create_inferior): Use
	construct_inferior_arguments instead of stringify_argv
	to get string representation which properly escapes
	special characters.
	* server.cc (handle_v_run): Just pass empty program arg
	as such, since any further processing is now handled via
	construct_inferior_arguments.

Change-Id: Ibf963fcd51415c948840fb463289516b3479b0c3

gdbserver/ChangeLog

@@ -1,3 +1,16 @@
+2020-05-25  Michael Weghorn  <m.weghorn@posteo.de>
+
+	PR gdbserver/25893
+	* linux-low.cc (linux_process_target::create_inferior),
+	lynx-low.cc (lynx_process_target::create_inferior),
+	win32-low.cc (win32_process_target::create_inferior): Use
+	construct_inferior_arguments instead of stringify_argv
+	to get string representation which properly escapes
+	special characters.
+	* server.cc (handle_v_run): Just pass empty program arg
+	as such, since any further processing is now handled via
+	construct_inferior_arguments.
+
 2020-05-25  Michael Weghorn  <m.weghorn@posteo.de>
 
 	* nto-low.cc (nto_process_target::create_inferior): Pass

gdbserver/linux-low.cc

@@ -984,7 +984,7 @@ linux_process_target::create_inferior (const char *program,
   {
     maybe_disable_address_space_randomization restore_personality
       (cs.disable_randomization);
-    std::string str_program_args = stringify_argv (program_args);
+    std::string str_program_args = construct_inferior_arguments (program_args);
 
     pid = fork_inferior (program,
 			 str_program_args.c_str (),

gdbserver/lynx-low.cc

@@ -253,7 +253,7 @@ lynx_process_target::create_inferior (const char *program,
 				      const std::vector<char *> &program_args)
 {
   int pid;
-  std::string str_program_args = stringify_argv (program_args);
+  std::string str_program_args = construct_inferior_arguments (program_args);
 
   lynx_debug ("create_inferior ()");
 

gdbserver/server.cc

@@ -2957,7 +2957,7 @@ handle_v_run (char *own_buf)
       else if (p == next_p)
 	{
 	  /* Empty argument.  */
-	  new_argv.push_back (xstrdup ("''"));
+	  new_argv.push_back (xstrdup (""));
 	}
       else
 	{

gdbserver/win32-low.cc

@@ -693,7 +693,7 @@ win32_process_target::create_inferior (const char *program,
   DWORD flags;
   PROCESS_INFORMATION pi;
   DWORD err;
-  std::string str_program_args = stringify_argv (program_args);
+  std::string str_program_args = construct_inferior_arguments (program_args);
   char *args = (char *) str_program_args.c_str ();
 
   /* win32_wait needs to know we're not attaching.  */