[Ada] Add a gnatbind option to generate C code

2019-07-03  Arnaud Charlet  <charlet@adacore.com>

gcc/ada/

	* bindgen.adb (Gen_Main): Disable generation of reference to
	Ada_Main_Program_Name for CCG.
	* bindusg.adb (Display): Add -G to the command-line usage for
	gnatbind.
	* opt.ads (Generate_C_Code): Update comment.
	* switch-b.adb (Scan_Binder_Switches): Add handling for -G.

From-SVN: r272965

gcc/ada/ChangeLog

 2019-07-03  Arnaud Charlet  <charlet@adacore.com>
 
+	* bindgen.adb (Gen_Main): Disable generation of reference to
+	Ada_Main_Program_Name for CCG.
+	* bindusg.adb (Display): Add -G to the command-line usage for
+	gnatbind.
+	* opt.ads (Generate_C_Code): Update comment.
+	* switch-b.adb (Scan_Binder_Switches): Add handling for -G.
+
+2019-07-03  Arnaud Charlet  <charlet@adacore.com>
+
 	* sem_ch7.adb (Has_Referencer): Do not consider inlined
 	subprograms when generating C code, which allows us to generate
 	static inline subprograms.

gcc/ada/bindgen.adb

@@ -1805,13 +1805,18 @@ package body Bindgen is
       --  referenced elsewhere in the generated program, but is needed by
       --  the debugger (that's why it is generated in the first place). The
       --  reference stops Ada_Main_Program_Name from being optimized away by
-      --  smart linkers, such as the AiX linker.
+      --  smart linkers.
 
       --  Because this variable is unused, we make this variable "aliased"
       --  with a pragma Volatile in order to tell the compiler to preserve
       --  this variable at any level of optimization.
 
-      if Bind_Main_Program and not CodePeer_Mode then
+      --  CodePeer and CCG do not need this extra code on the other hand.
+
+      if Bind_Main_Program
+        and then not CodePeer_Mode
+        and then not Generate_C_Code
+      then
          WBI ("      Ensure_Reference : aliased System.Address := " &
               "Ada_Main_Program_Name'Address;");
          WBI ("      pragma Volatile (Ensure_Reference);");

gcc/ada/bindusg.adb

@@ -133,6 +133,11 @@ package body Bindusg is
       Write_Line
         ("  -F        Force checking of elaboration Flags");
 
+      --  Line for -G switch
+
+      Write_Line
+        ("  -G        Generate binder file suitable for CCG");
+
       --  Line for -h switch
 
       Write_Line

gcc/ada/opt.ads

@@ -746,9 +746,9 @@ package Opt is
    --  file name with extension stripped.
 
    Generate_C_Code : Boolean := False;
-   --  GNAT
+   --  GNAT, GNATBIND
    --  If True, the Cprint circuitry to generate C code output is activated.
-   --  Set True by use of -gnateg or -gnatd.V.
+   --  Set True by use of -gnateg or -gnatd.V for GNAT, and -G for GNATBIND.
 
    Generate_CodePeer_Messages : Boolean := False;
    --  GNAT

gcc/ada/switch-b.adb

@@ -294,6 +294,12 @@ package body Switch.B is
                Debugger_Level := 2;
             end if;
 
+         --  Processing for G switch
+
+         when 'G' =>
+            Ptr := Ptr + 1;
+            Generate_C_Code := True;
+
          --  Processing for h switch
 
          when 'h' =>