[Bug gcov-profile/80911] gcov failed: gcno corrupted

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80911

--- Comment #17 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Martin Liška from comment #2)
> Can't confirm that, running trunk@248556 works fine for me.
> Utilizing valgrind also does not help.

I also had problems reproducing the problem, so I decided to dig a little
further.

The problem occurred for me with g++ 4.4.3.

With a more recent g++ (5.4.0), we generate at gimplify:
...
              D.67316 = {};
              block_info::block_info (&D.67316);
              try
                {
                  D.74239 = gcov_read_unsigned ();
                  D.74240 = (long unsigned int) D.74239;
                  D.74241 = &fn->blocks;
                  std::vector<block_info>::resize (D.74241, D.74240, &D.67316);
                }
              finally
                {
                  block_info::~block_info (&D.67316);
                  D.67316 = {CLOBBER};
                }
...
In other words, before calling the default constructor block_info::block_info
on the implicit resize argument D.67316, we initialize it to zero using
'D.67316 = {}'.

With 4.4.3, we generate:
...
          __comp_ctor  (&D.67200);
          try
            {
              D.67371 = gcov_read_unsigned ();
              D.67372 = (long unsigned int) D.67371;
              D.67373 = &fn->blocks;
              resize (D.67373, D.67372, &D.67200);
            }
          finally
            {
              __comp_dtor  (&D.67200);
            }
...
and we don't initialize all of D.67200 to zero.

So, when compiling with a more recent compiler, the initialization is done
regardless of how the default constructor is implemented, so there's no problem
to detect with valgrind.