[Darwin, testsuite, committed] Address PR91087 - XFAIL parts of pr16855.C.

[Iain Sandoe]

The testcase is failing to instrument part of the source because of a platform
bug in the ordering of static DTORs.  It seems unlikely that this is generically
fixable in the toolchain (and given that it's likely to be a dynamic loader
change would not be expected to be applied retrospectively to OS versions
that are out of support).  To avoid the testsuite noise, xfail the count lines
that don't match (we can adjust the xfails as/when the upstream bug is fixed).

dejagnu xfails do not seem to work when embedded in a line like:
  ~Test (void) { .... /* count(1) { xfail ... } */ }
the closing brace seems to confuse the parser.  The solution is to exapnd the
text onto three lines.

as an aside, *not part of the applied patch*:
FWIW, I think we should consider that if the correct operation of the coverage
depends on CTOR priority there’s no point in setting it to the default when the
target doesn’t support CTOR priorities - we might as well leave it as desired
and at least that will DTRT within a single TU or under LTO.

tested on x86-64-darwin16, x86_64-pc-linuc-gnu,
applied to mainline
thanks
Iain

2019-07-25  Iain Sandoe  <i...@sandoe.co.uk>

        PR gcov-profile/91087
        * g++.dg/gcov/pr16855.C: Xfail the count lines for the DTORs and the
        "final" line for the failure summaries.  Adjust source layout so that
        dejagnu xfail expressions work.

diff --git a/gcc/testsuite/g++.dg/gcov/pr16855.C 
b/gcc/testsuite/g++.dg/gcov/pr16855.C
index d7aa8a4f72..a68b05cb57 100644
--- a/gcc/testsuite/g++.dg/gcov/pr16855.C
+++ b/gcc/testsuite/g++.dg/gcov/pr16855.C
@@ -1,6 +1,8 @@
 /* { dg-options "-fprofile-arcs -ftest-coverage" } */
 /* { dg-do run { target native } } */
 
+/* See PR91087 for information on Darwin xfails. */
+
 #include <stdlib.h>
 #include <stdio.h>
 
@@ -18,7 +20,9 @@ class Test
 {
 public:
   Test (void) { fprintf (stderr, "In Test::Test\n"); /* count(1) */ }
-  ~Test (void) { fprintf (stderr, "In Test::~Test\n"); /* count(1) */ }
+  ~Test (void) {
+   fprintf (stderr, "In Test::~Test\n"); /* count(1) { xfail *-*-darwin* } */
+  }
 } T1;
 
 void
@@ -42,7 +46,7 @@ static void __attribute__ ((constructor)) ctor_default ()
 
 static void __attribute__ ((destructor)) dtor_default ()
 {
-  fprintf (stderr, "in destructor(())\n"); /* count(1) */
+  fprintf (stderr, "in destructor(())\n"); /* count(1) { xfail *-*-darwin* } */
 }
 
-/* { dg-final { run-gcov branches { -b pr16855.C } } } */
+/* { dg-final { run-gcov branches { -b pr16855.C } { xfail *-*-darwin* } } } */