[Ada] Argument_String_To_List creates empty items from whitespace

This patch corrects an issue whereby leading whitespace in a non-quoted
argument list passed to Argument_String_To_List caused extraneous empty
arguments to be returned.

2018-07-17  Justin Squirek  <squirek@adacore.com>

gcc/ada/

	* libgnat/s-os_lib.adb (Argument_String_To_List): Fix trimming of
	whitespace.

gcc/testsuite/

	* gnat.dg/split_args.adb: New testcase.

From-SVN: r262783

gcc/ada/ChangeLog

+2018-07-17  Justin Squirek  <squirek@adacore.com>
+
+	* libgnat/s-os_lib.adb (Argument_String_To_List): Fix trimming of
+	whitespace.
+
 2018-07-17  Hristian Kirtchev  <kirtchev@adacore.com>
 
 	* sem_prag.adb (Has_Visible_State): Do not consider constants as

gcc/ada/libgnat/s-os_lib.adb

@@ -178,7 +178,6 @@ package body System.OS_Lib is
 
       return Len;
    end Args_Length;
-
    -----------------------------
    -- Argument_String_To_List --
    -----------------------------
@@ -191,6 +190,9 @@ package body System.OS_Lib is
       Idx      : Integer;
       New_Argc : Natural := 0;
 
+      Backqd : Boolean := False;
+      Quoted : Boolean := False;
+
       Cleaned     : String (1 .. Arg_String'Length);
       Cleaned_Idx : Natural;
       --  A cleaned up version of the argument. This function is taking
@@ -205,14 +207,17 @@ package body System.OS_Lib is
       Idx := Arg_String'First;
 
       loop
-         exit when Idx > Arg_String'Last;
+         --  Skip extraneous spaces
 
-         declare
-            Backqd  : Boolean := False;
-            Quoted  : Boolean := False;
+         while Idx <= Arg_String'Last and then Arg_String (Idx) = ' ' loop
+            Idx := Idx + 1;
+         end loop;
+
+         exit when Idx > Arg_String'Last;
 
-         begin
          Cleaned_Idx := Cleaned'First;
+         Backqd      := False;
+         Quoted      := False;
 
          loop
             --  An unquoted space is the end of an argument
@@ -267,13 +272,6 @@ package body System.OS_Lib is
          New_Argc := New_Argc + 1;
          New_Argv (New_Argc) :=
            new String'(Cleaned (Cleaned'First .. Cleaned_Idx - 1));
-
-            --  Skip extraneous spaces
-
-            while Idx <= Arg_String'Last and then Arg_String (Idx) = ' ' loop
-               Idx := Idx + 1;
-            end loop;
-         end;
       end loop;
 
       return new Argument_List'(New_Argv (1 .. New_Argc));

gcc/testsuite/ChangeLog

+2018-07-17  Justin Squirek  <squirek@adacore.com>
+
+	* gnat.dg/split_args.adb: New testcase.
+
 2018-07-17  Ed Schonberg  <schonberg@adacore.com>
 
 	* gnat.dg/discr54.adb, gnat.dg/discr54_pkg.ads: New testcase.

gcc/testsuite/gnat.dg/split_args.adb

+--  { dg-do run }
+--  { dg-options "-gnatws" }
+
+with System.OS_Lib; use System.OS_Lib;
+
+procedure Split_Args is
+   X : constant Argument_List_Access :=
+     Argument_String_To_List (" -v");
+begin
+   if X'Length /= 1 then
+      raise Program_Error;
+   end if;
+end Split_Args;