C/C++ instr: consider other compiler switches for preprocessing

We must launch the preprocessing command with all of the switches that
can influence the preprocessing of the file. We used to consider macro
definition / undefinition and the C/C++ standard set by the -std switch
but there are more switches than that (the list is unfortunately
probably not exhaustive): -fno-rtti (do not include runtime type
information) and all of the warnings switches which can influence the
preprocessing through the __has_warning macro.

Author: Jugst3r

testsuite/tests/instr-cov/C++/109-pp-switches/main.cpp

@@ -0,0 +1,7 @@
+#include <typeinfo>
+
+int
+main (int argc, char **argv)
+{
+  return 0;
+}

testsuite/tests/instr-cov/C++/109-pp-switches/test.py

@@ -0,0 +1,33 @@
+"""
+Check that the instrumenter considers the -fno-rtti switch for preprocessing.
+"""
+
+from SCOV.minicheck import build_run_and_coverage, check_xcov_reports
+from SCOV.instr import xcov_instrument
+from SUITE.context import thistest
+from SUITE.cutils import Wdir
+from SUITE.tutils import gprbuild, gprfor
+from SUITE.gprutils import GPRswitches
+
+
+tmp = Wdir("tmp_")
+
+build_run_and_coverage(
+    gprsw=GPRswitches(root_project=gprfor(srcdirs=[".."], mains=["main.cpp"])),
+    covlevel="stmt",
+    mains=["main"],
+    extra_instr_args=["--c++-opts=-fno-rtti"],
+    extra_gprbuild_cargs=["-fno-rtti"],
+    extra_coverage_args=["-axcov", "--output-dir=xcov"],
+    trace_mode="src",
+)
+
+check_xcov_reports(
+    "*.xcov",
+    {
+        "main.cpp.xcov": {"+": {6}},
+    },
+    "xcov",
+)
+
+thistest.result()

tools/gnatcov/instrument-c.adb

@@ -80,15 +80,11 @@ package body Instrument.C is
    type Macro_Set_Cst_Access is access constant Macro_Set;
 
    function Builtin_Macros
-     (Lang, Compiler, Std, Output_Dir : String) return Macro_Set_Cst_Access;
-   --  Return the list of built-in macros for the given compiler, standard and
-   --  language. Output_Dir is used to store a temporary file.
-   --
-   --  Note that we could generate a fully-fledged preprocessor configuration
-   --  (the standard macros + the command-line defined macros with an
-   --  additional argument there), but it is more convenient to cache the
-   --  "light" preprocessor configuration that is determined by the compiler,
-   --  language and standard only.
+     (Lang, Compiler, Output_Dir : String;
+      Compiler_Switches : String_Vectors.Vector) return Macro_Set_Cst_Access;
+   --  Return the list of built-in macros for the given compiler, language and
+   --  according to the compiler switches. Output_Dir is used to store a
+   --  temporary file.
 
    procedure Preprocess_Source
      (Filename      : String;
@@ -2524,16 +2520,15 @@ package body Instrument.C is
    --------------------
 
    function Builtin_Macros
-     (Lang, Compiler, Std, Output_Dir : String) return Macro_Set_Cst_Access
+     (Lang, Compiler, Output_Dir : String;
+      Compiler_Switches : String_Vectors.Vector) return Macro_Set_Cst_Access
    is
       use Ada.Characters.Handling;
 
       PID : constant Unsigned_64 :=
         Unsigned_64 (Pid_To_Integer (Current_Process_Id));
 
       L      : constant String := To_Lower (Lang);
-      Key    : constant Unbounded_String :=
-        +Compiler & " -x " & L & " " & Std;
       Result : constant Macro_Set_Access := new Macro_Set;
 
       Args     : String_Vectors.Vector;
@@ -2549,18 +2544,15 @@ package body Instrument.C is
 
       Args.Append (+"-x");
       Args.Append (+L);
-      if Std'Length /= 0 then
-         Args.Append (+Std);
-      end if;
+      Args.Append (Compiler_Switches);
       Args.Append (+"-E");
       Args.Append (+"-dM");
       Args.Append (+"-");
 
       Run_Command
         (Command             => Compiler,
          Arguments           => Args,
-         Origin_Command_Name =>
-           "getting built-in macros for " & (+Key),
+         Origin_Command_Name => "gnatcov instrument",
          Output_File         => Filename,
          In_To_Null          => True);
 
@@ -4532,8 +4524,8 @@ package body Instrument.C is
         Builtin_Macros
           (Image (C_Family_Language (Instrumenter.Language)),
            +Prj.Compiler_Driver (Instrumenter.Language),
-           +Self.Std,
-           +Prj.Output_Dir).all;
+           +Prj.Output_Dir,
+           Self.Compiler_Switches).all;
    end Import_Options;
 
    ---------------------------

tools/gnatcov/instrument-common.adb

@@ -473,13 +473,13 @@ package body Instrument.Common is
          Add_Macro_Switches (Options.PP_Macros);
       end if;
 
-      --  The -std switch also indicates the C/C++ version used, and
-      --  influences both the configuration of the preprocessor, and the
-      --  parsing of the file.
+      --  Add other compiler switches as they may also influence both the
+      --  configuration of the preprocessor, and the parsing of the file. A
+      --  non-exhaustive list includes undefining macros through -U switches,
+      --  using -std to change the C++ standard in use, -fno-rtti to prevent
+      --  inclusion of runtime type information etc.
 
-      if Length (Options.Std) /= 0 then
-         Args.Append (Options.Std);
-      end if;
+      Args.Append (Options.Compiler_Switches);
 
    end Add_Options;
 
@@ -638,11 +638,21 @@ package body Instrument.Common is
 
             elsif Read_With_Argument (A, 'U', Value) then
                Self.PP_Macros.Include ((Define => False, Name => Value));
+               --  Account for all the switches that can influence the file
+               --  preprocessing.
 
-            elsif Has_Prefix (A, "-std=") then
-               Self.Std := +A;
-            end if;
+            elsif Has_Prefix (A, "-std")
+              or else Has_Prefix (A, "-fno-rtti")
+              or else Has_Prefix (A, "-fno-exceptions")
 
+              --  All the warning switches can influence the preprocessing
+              --  through the use of the __has_warning macro, e.g.
+              --  #if __has_warning("-Wimplicit-fallthrough")
+
+              or else Has_Prefix (A, "-W")
+            then
+               Self.Compiler_Switches.Append (+A);
+            end if;
             I := I + 1;
          end;
       end loop;

tools/gnatcov/instrument-common.ads

@@ -552,9 +552,10 @@ package Instrument.Common is
       PP_Macros : Macro_Set;
       --  Set of macros for the preprocessor
 
-      Std : Unbounded_String;
-      --  -std=X argument to pass to the preprocessor and the parser, or the
-      --  empty string.
+      Compiler_Switches : String_Vectors.Vector;
+      --  List of compiler switches that can influence the file preprocessing.
+      --  The list should be amended alongside our discoveries. It is
+      --  currently: -std, -fno-exceptions, -fno-rtti, -W* switches.
    end record;
    --  Options to analyze (preprocess and/or parse) a compilation unit