[Bug gcov-profile/83878] New: Line hit counts are sometimes wrong

[mcastelluccio at mozilla dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83878

            Bug ID: 83878
           Summary: Line hit counts are sometimes wrong
           Product: gcc
           Version: unknown
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: gcov-profile
          Assignee: unassigned at gcc dot gnu.org
          Reporter: mcastelluccio at mozilla dot com
                CC: marxin at gcc dot gnu.org
  Target Milestone: ---

Created attachment 43143
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=43143&action=edit
Archive with GCNO, GCDA, source file and GCOV output

I'm attaching an archive with gcno, gcda, cpp and gcov files that shows the
problem.

See for example after line 3181:
>         -: 3181:static bool
> function _ZL24DefineSelfHostedPropertyP9JSContextN2JS6HandleIP8JSObjectEENS2_I4jsidEEPKcS9_j called 28803 returned 100% blocks executed 65%
>     28803: 3182:DefineSelfHostedProperty(JSContext* cx, HandleObject obj, HandleId id,
>     28803: 3182-block  0
>         -: 3183:                         const char* getterName, const char* setterName,
>         -: 3184:                         unsigned attrs)
>         -: 3185:{
>     28803: 3186:    JSAtom* getterNameAtom = Atomize(cx, getterName, strlen(getterName));
>     28803: 3186-block  0
> call    0 returned 28803
>     28803: 3187:    if (!getterNameAtom)
> branch  0 taken 28803 (fallthrough)
> branch  1 taken 0
>         -: 3188:        return false;
>     57606: 3189:    RootedPropertyName getterNameName(cx, getterNameAtom->asPropertyName());
>         -: 3190:

Why does line 3189 have a hit count twice as big as previous lines and the
function itself?

The files were generated with GCC 6, we are going to try compiling with a new
version soon. Do you already know of similar problems that have been fixed
between 6 and 8?