Merge branch 'eyraud/c++_constexpr' into 'master'

C++ instr: do not instrument constexpr

See merge request eng/cov/gnatcoverage!233

Instrumenting constexpr functions violates the constexpr semantics and
there is no straightforward valid way of instrumenting such code
constructs.

Skip their instrumentation altogether for the moment, as their use is
quite limited (they are only allowed to return literal values).

Ref: eng/cov/gnatcoverage#101

Author: Jugst3r

.pre-commit-config.yaml

@@ -13,7 +13,6 @@ repos:
             IndentExternBlock: NoIndent,
 
             SpaceAfterCStyleCast: true,
-            UseTab: ForContinuationAndIndentation,
             SpacesInLineCommentPrefix: {
               Minimum: 0,
               Maximum: -1

testsuite/SCOV/internals/driver.py

@@ -1301,7 +1301,8 @@ def mode_build(self):
             dump_trigger=self.dump_trigger,
             gprsw=instrument_gprsw,
             gpr_obj_dir=self.gpr_obj_dir,
-            out=out)
+            out=out,
+            tolerate_messages=self.testcase.tolerate_messages)
 
         # When exception propagation is not available, a test ending with an
         # unhandled exception goes straight to the last_chance_handler from
@@ -1328,11 +1329,12 @@ def mode_build(self):
         # Standard output might contain warnings indicating instrumentation
         # issues. This should not happen, so simply fail as soon as the output
         # file is not empty.
-        thistest.fail_if(
-            os.path.getsize(out) > 0,
-            'xcov instrument standard output not empty ({}):'
-            '\n--'
-            '\n{}'.format(out, contents_of(out)))
+        if not self.testcase.tolerate_messages:
+            thistest.fail_if(
+                os.path.getsize(out) > 0,
+                'xcov instrument standard output not empty ({}):'
+                '\n--'
+                '\n{}'.format(out, contents_of(out)))
 
         # Now we can build, instructing gprbuild to fetch the instrumented
         # sources in their dedicated subdir:

testsuite/SCOV/tc.py

@@ -123,11 +123,16 @@ def __drivers_from(self, cspec):
         # match this expression
         return [drv for drv in self.all_drivers if re.search(drv_expr, drv)]
 
-    def __init__(self, extradrivers="", extracargs="", category=CAT.auto):
+    def __init__(self, extradrivers="", extracargs="", category=CAT.auto,
+                 tolerate_messages=None):
         # By default, these test cases expect no error from subprocesses (xrun,
         # xcov, etc.)
         self.expect_failures = False
 
+        # Pass tolerate_messages to gnatcov instrument invocations (see the doc
+        # for xcov_instrument).
+        self.tolerate_messages = tolerate_messages
+
         # Step 1: Compute the list of drivers and consolidation specs
         #         to exercise
         # ------------------------------------------------------------

testsuite/tests/C++/mcdc/ConstExpr/src/test_constexpr.cpp

@@ -0,0 +1,28 @@
+constexpr int
+foo ()
+{
+  if (true && false)       // # ce-body
+    return 1;              // # ce-body
+  constexpr bool a = true; // # ce-body
+  if constexpr (false)     // # ce-body
+    return 1;              // # ce-body
+  return 0;                // # ce-body
+}
+
+int
+main(){
+  constexpr bool a = true || false;                    // # single-ce-decl
+  constexpr bool b = true || false, c = true || false; // # double-ce-decl
+  if constexpr (false)                                 // # if-ce
+    return 1;                                          // # if-rt
+  return 0;                                            // # rt
+}
+
+//# test_constexpr.cpp
+//
+//    /ce-body/        l? ## s?
+//    /single-ce-decl/ l? ## d?
+//    /double-ce-decl/ l? ## d?, d?
+//    /if-ce/          l? ## d?
+//    /if-rt/          l- ## s-
+//    /rt/             l+ ## 0

testsuite/tests/C++/mcdc/ConstExpr/test.py

@@ -0,0 +1,5 @@
+from SCOV.tc import TestCase
+from SUITE.context import thistest
+
+TestCase(tolerate_messages=r".* cannot instrument constexpr").run()
+thistest.result()

tools/gnatcov/clang-extensions.adb

@@ -90,6 +90,20 @@ package body Clang.Extensions is
       return Opcode_Str;
    end Get_Opcode_Str;
 
+   ------------------
+   -- Is_Constexpr --
+   ------------------
+
+   function Is_Constexpr (C : Cursor_T) return Boolean
+   is
+      function Is_Constexpr_C (C : Cursor_T) return unsigned
+        with
+          Import, Convention => C,
+          External_Name => "clang_isConstexpr";
+   begin
+      return Is_Constexpr_C (C) /= 0;
+   end Is_Constexpr;
+
    -----------------------------------
    -- CX_Rewriter_Insert_Text_After --
    -----------------------------------

tools/gnatcov/clang-extensions.ads

@@ -88,6 +88,8 @@ package Clang.Extensions is
 
    function Get_Callee_Name_Str (C : Cursor_T) return String with Inline;
 
+   function Is_Constexpr (C : Cursor_T) return Boolean with Inline;
+
    function Unwrap (C : Cursor_T) return Cursor_T
      with Import, Convention => C, External_Name => "clang_unwrap";