Make '{add-,}symbol-file' not care about the position of command line arguments

This is a bug that's been detected while doing the readnever work.

If you use 'symbol-file' or 'add-symbol-file', the position of each
argument passed to the command matters.  This means that if you do:

  (gdb) symbol-file -readnow /foo/bar

The symbol file specified will (correctly) have all of its symbols
read by GDB (because of the -readnow flag).  However, if you do:

  (gdb) symbol-file /foo/bar -readnow

GDB will silently ignore the -readnow flag, because it was specified
after the filename.  This is not a good thing to do and may confuse
the user.

To address that, I've modified the argument parsing mechanisms of
symbol_file_command and add_symbol_file_command to be
"position-independent".  I have also added one error call at the end
of add_symbol_file_command's argument parsing logic, which now clearly
complains if no filename has been specified.  Both commands now
support the "--" option to stop argument processing.

This patch provides a testcase for both commands, in order to make
sure that the argument order does not matter.  It has been
regression-tested on BuildBot.

gdb/ChangeLog:

2017-12-01  Sergio Durigan Junior  <sergiodj@redhat.com>

	* symfile.c (symbol_file_command): Call
	'symbol_file_add_main_1' only after processing all command
	line options.
	(add_symbol_file_command): Modify logic to make arguments
	position-independent.

gdb/testsuite/ChangeLog:

2017-12-01  Sergio Durigan Junior  <sergiodj@redhat.com>

	* gdb.base/relocate.exp: Add tests to guarantee that arguments
	to 'symbol-file' and 'add-symbol-file' can be
	position-independent.

1 files changed, 51 insertions, 47 deletions

diff --git a/gdb/symfile.c b/gdb/symfile.c
index 4bbe0b5a62..1c9f836eb3 100644
--- a/gdb/symfile.c
+++ b/gdb/symfile.c
@@ -1622,26 +1622,35 @@ symbol_file_command (const char *args, int from_tty)
       objfile_flags flags = OBJF_USERLOADED;
       symfile_add_flags add_flags = 0;
       char *name = NULL;
+      bool stop_processing_options = false;
+      int idx;
+      char *arg;
 
       if (from_tty)
 	add_flags |= SYMFILE_VERBOSE;
 
       gdb_argv built_argv (args);
-      for (char *arg : built_argv)
+      for (arg = built_argv[0], idx = 0; arg != NULL; arg = built_argv[++idx])
 	{
-	  if (strcmp (arg, "-readnow") == 0)
-	    flags |= OBJF_READNOW;
-	  else if (*arg == '-')
-	    error (_("unknown option `%s'"), arg);
-	  else
+	  if (stop_processing_options || *arg != '-')
 	    {
-	      symbol_file_add_main_1 (arg, add_flags, flags);
-	      name = arg;
+	      if (name == NULL)
+		name = arg;
+	      else
+		error (_("Unrecognized argument \"%s\""), arg);
 	    }
+	  else if (strcmp (arg, "-readnow") == 0)
+	    flags |= OBJF_READNOW;
+	  else if (strcmp (arg, "--") == 0)
+	    stop_processing_options = true;
+	  else
+	    error (_("Unrecognized argument \"%s\""), arg);
 	}
 
       if (name == NULL)
 	error (_("no symbol file name was specified"));
+
+      symbol_file_add_main_1 (name, add_flags, flags);
     }
 }
 
@@ -2180,8 +2189,6 @@ add_symbol_file_command (const char *args, int from_tty)
   char *arg;
   int argcnt = 0;
   int sec_num = 0;
-  int expecting_sec_name = 0;
-  int expecting_sec_addr = 0;
   struct objfile *objf;
   objfile_flags flags = OBJF_USERLOADED | OBJF_SHARED;
   symfile_add_flags add_flags = 0;
@@ -2196,7 +2203,8 @@ add_symbol_file_command (const char *args, int from_tty)
   };
 
   struct section_addr_info *section_addrs;
-  std::vector<sect_opt> sect_opts;
+  std::vector<sect_opt> sect_opts = { { ".text", NULL } };
+  bool stop_processing_options = false;
   struct cleanup *my_cleanups = make_cleanup (null_cleanup, NULL);
 
   dont_repeat ();
@@ -2204,63 +2212,59 @@ add_symbol_file_command (const char *args, int from_tty)
   if (args == NULL)
     error (_("add-symbol-file takes a file name and an address"));
 
+  bool seen_addr = false;
   gdb_argv argv (args);
 
   for (arg = argv[0], argcnt = 0; arg != NULL; arg = argv[++argcnt])
     {
-      /* Process the argument.  */
-      if (argcnt == 0)
-	{
-	  /* The first argument is the file name.  */
-	  filename.reset (tilde_expand (arg));
-	}
-      else if (argcnt == 1)
-	{
-	  /* The second argument is always the text address at which
-	     to load the program.  */
-	  sect_opt sect = { ".text", arg };
-	  sect_opts.push_back (sect);
-	}
-      else
+      if (stop_processing_options || *arg != '-')
 	{
-	  /* It's an option (starting with '-') or it's an argument
-	     to an option.  */
-	  if (expecting_sec_name)
+	  if (filename == NULL)
 	    {
-	      sect_opt sect = { arg, NULL };
-	      sect_opts.push_back (sect);
-	      expecting_sec_name = 0;
+	      /* First non-option argument is always the filename.  */
+	      filename.reset (tilde_expand (arg));
 	    }
-	  else if (expecting_sec_addr)
+	  else if (!seen_addr)
 	    {
-	      sect_opts.back ().value = arg;
-	      expecting_sec_addr = 0;
-	    }
-	  else if (strcmp (arg, "-readnow") == 0)
-	    flags |= OBJF_READNOW;
-	  else if (strcmp (arg, "-s") == 0)
-	    {
-	      expecting_sec_name = 1;
-	      expecting_sec_addr = 1;
+	      /* The second non-option argument is always the text
+		 address at which to load the program.  */
+	      sect_opts[0].value = arg;
+	      seen_addr = true;
 	    }
 	  else
 	    error (_("Unrecognized argument \"%s\""), arg);
 	}
+      else if (strcmp (arg, "-readnow") == 0)
+	flags |= OBJF_READNOW;
+      else if (strcmp (arg, "-s") == 0)
+	{
+	  if (argv[argcnt + 1] == NULL)
+	    error (_("Missing section name after \"-s\""));
+	  else if (argv[argcnt + 2] == NULL)
+	    error (_("Missing section address after \"-s\""));
+
+	  sect_opt sect = { argv[argcnt + 1], argv[argcnt + 2] };
+
+	  sect_opts.push_back (sect);
+	  argcnt += 2;
+	}
+      else if (strcmp (arg, "--") == 0)
+	stop_processing_options = true;
+      else
+	error (_("Unrecognized argument \"%s\""), arg);
     }
 
+  if (filename == NULL)
+    error (_("You must provide a filename to be loaded."));
+
   /* This command takes at least two arguments.  The first one is a
      filename, and the second is the address where this file has been
      loaded.  Abort now if this address hasn't been provided by the
      user.  */
-  if (sect_opts.empty ())
+  if (!seen_addr)
     error (_("The address where %s has been loaded is missing"),
 	   filename.get ());
 
-  if (expecting_sec_name)
-    error (_("Missing section name after \"-s\""));
-  else if (expecting_sec_addr)
-    error (_("Missing section address after \"-s\""));
-
   /* Print the prompt for the query below.  And save the arguments into
      a sect_addr_info structure to be passed around to other
      functions.  We have to split this up into separate print