Instrument.C: only pass builtin macros when needed

We should avoid passing builtin macros to the actual preprocessor: we
will just end up redefining all of the macros, and this will result in
warnings at coverage time, as we are preprocessing again the code for
some report formats (such as xml).

Change-Id: I3c6da05e0efd84b31d1fbd55261dd1dc064897a6
TN: V914-024

Author: Jugst3r

tools/gnatcov/instrument-c.adb

@@ -2420,7 +2420,7 @@ package body Instrument.C is
       --  Add the preprocessing flag
 
       Append_Arg (Cmd, "-E");
-      Add_Options (Cmd.Arguments, Options);
+      Add_Options (Cmd.Arguments, Options, Pass_Builtins => False);
 
       Append_Arg (Cmd, Filename);
 
@@ -3822,8 +3822,9 @@ package body Instrument.C is
    -----------------
 
    procedure Add_Options
-     (Args : in out String_Vectors.Vector; Options : Analysis_Options)
-   is
+     (Args          : in out String_Vectors.Vector;
+      Options       : Analysis_Options;
+      Pass_Builtins : Boolean := True) is
 
       procedure Add_Macro_Switches (Macros : Macro_Vectors.Vector);
       --  Add the given macro switches to Args
@@ -3856,7 +3857,9 @@ package body Instrument.C is
       --  latter should have precedence over builtins and thus must come last
       --  in Args.
 
-      Add_Macro_Switches (Options.Builtin_Macros);
+      if Pass_Builtins then
+         Add_Macro_Switches (Options.Builtin_Macros);
+      end if;
       Add_Macro_Switches (Options.PP_Macros);
 
       --  The -std switch also indicates the C/C++ version used, and

tools/gnatcov/instrument-c.ads

@@ -250,8 +250,11 @@ package Instrument.C is
    --  Options to analyze (preprocess and/or parse) a compilation unit
 
    procedure Add_Options
-     (Args : in out String_Vectors.Vector; Options : Analysis_Options);
-   --  Append to Args the command line options corresponding to Options
+     (Args          : in out String_Vectors.Vector;
+      Options       : Analysis_Options;
+      Pass_Builtins : Boolean := True);
+   --  Append to Args the command line options corresponding to Options. If
+   --  Pass_Builtins is True, pass builtin macros in Options to Args.
 
    procedure Import_From_Project
      (Self     : out Analysis_Options;