Merge branch 'topic/401-M-preprocessor-flags' into 'master'

Integrated instr: Properly handle -M family of switches

Closes #401

See merge request eng/das/cov/gnatcoverage!817

These preprocessor flags imply -E, so there is nothing to do on the gnatcov side.

Closes eng/das/cov/gnatcoverage#401

Author: Jugst3r

testsuite/tests/integrated_instrumentation/401-M-flags/special_0.h

@@ -0,0 +1 @@
+const int special_0 = 0;

testsuite/tests/integrated_instrumentation/401-M-flags/test.c

@@ -0,0 +1,7 @@
+#include "special_0.h"
+
+int
+main ()
+{
+  return special_0;
+}

testsuite/tests/integrated_instrumentation/401-M-flags/test.py

@@ -0,0 +1,60 @@
+"""
+Test that the output of the -M family of flags of the GCC preprocessor is not
+clobbered with references to instrumentation artifacts.
+"""
+
+import os
+import os.path
+
+from e3.fs import cp
+
+from SUITE.control import env
+from SUITE.cutils import contents_of, Wdir
+from SUITE.tutils import cmdrun, thistest, xcov
+
+Wdir("tmp_")
+
+cwd = os.getcwd()
+
+# Copy the sources in the temporary directory
+cp(os.path.join("..", "test.c"), ".")
+cp(os.path.join("..", "special_0.h"), ".")
+
+# Then, setup the instrumentation process
+xcov(
+    [
+        "setup-integration",
+        "--level=stmt",
+        f"--files={os.path.join(cwd, 'test.c')}",
+        "--compilers=gcc",
+        f"--output-dir={cwd}",
+    ]
+)
+baseline_dep_file = "test.dep.expected"
+compile_cmd = [
+    "gcc",
+    "test.c",
+    "-MM",
+    "-MF",
+    baseline_dep_file,
+]
+
+# Generate the baseline dep file with the regular compiler
+cmdrun(compile_cmd, for_pgm=False)
+
+# Shadow the compiler driver with the generated wrapper
+env.add_search_path(env_var="PATH", path=cwd)
+
+# Ask gcc to produce a dep file, using the gnatcov wrapper this time
+dep_file = "test.dep.actual"
+compile_cmd.pop()
+compile_cmd.append(dep_file)
+cmdrun(compile_cmd, for_pgm=False)
+
+thistest.fail_if_not_equal(
+    what="Difference in generated dep file",
+    expected=contents_of(baseline_dep_file),
+    actual=contents_of(dep_file),
+)
+
+thistest.result()

tools/gnatcov/instrument-gcc_wrapper.adb

@@ -655,12 +655,24 @@ is
             Arg     : constant Unbounded_String := Element (Cur);
             Arg_Str : constant String := +Arg;
          begin
+            --  Include family switches will have already had an effect during
+            --  the initial preprocessing, skip them here
+
             if Arg_Str in "-include" | "--include" then
                Cur := Next (Cur);
             elsif Starts_With (Arg, "--include=")
               or else Starts_With (Arg, "-include")
             then
                null;
+
+            --  The -M family of switches should not be propagated as it
+            --  otherwise leads to the inclusion of coverage artifacts in the
+            --  generated dependency files.
+
+            elsif Arg_Str in "-MF" | "-MT" | "-MQ" then
+               Next (Cur);
+            elsif Starts_With (Arg, "-M") then
+               null;
             else
                Result.Append (Element (Cur));
             end if;
@@ -758,9 +770,13 @@ begin
 
    --  If this driver invocation is not meant to compile a source file, there
    --  is no instrumentation to do: just run the original driver and exit.
+   --
+   --  The -M family of flags imply -E, so there nothing to do for us in that
+   --  case too, EXCEPT FOR -MD and -MMD, which do not imply -E. See section
+   --  13 of the C preprocessor manual.
 
    for Arg of Cargs loop
-      if +Arg in "-###" | "-E" then
+      if +Arg in "-###" | "-E" | "-M" | "-MM" then
          Run_Original_Compiler (Context, Cargs);
          return;
       end if;