[Bug c/110072] New: __gcov_dump cannot generate gcda for so files opened with dlopen when gcc version is later than 5.1.0

["rc452860 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=110072

            Bug ID: 110072
           Summary: __gcov_dump cannot generate gcda for so files opened
                    with dlopen when gcc version is later than 5.1.0
           Product: gcc
           Version: 4.8.5
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: rc452860 at gmail dot com
  Target Milestone: ---

Created attachment 55229
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55229&action=edit
example

When the version of gcc is lower than 5.1.0, __gcov_dump cannot generate gcda
files for the so files opened by dlopen.

See attachment for sample project.

After comparing the different versions of GCC code, I found that gcc before
5.1.0 stored counter data in gcov_list, while later versions of GCC stored it
in __gcov_master.

The two versions are defined as follows:

gcc4.8.5 in libgcc/libgcov.c
```
/* Chain of per-object gcov structures.  */
static struct gcov_info *gcov_list;
```

gcc8.5.0 in libgcc/libgcov-driver.c
```
/* Exactly one of these will be live in the process image.  */
struct gcov_master __gcov_master = 
  {GCOV_VERSION, 0};
```