3.6.1 Nomination: r232438, r232443, and clang/r232439, which fix pr22436

[Tom Stellard]

On Thu, Apr 30, 2015 at 11:23:31PM -0400, Tom Stellard wrote:
> Hi Justin,
> 
> I've merged these patches:
> 
> On Wed, Apr 29, 2015 at 10:00:15AM -0700, Justin Bogner wrote:
> > Hey Tom, can you cherry pick these three patches, which collectively fix
> > llvm.org/pr22436, to the 3.6 branch? I'm the code owner for profiling
> > and coverage instrumentation and this is a pretty straightforward bug
> > fix.
> > 
> >   llvm/r232438:
> 
> r236303
> 

Hi Justin,

It turns out that this commit breaks the libLLVM.so ABI, because the
size of the GCOVOptions class.  I think we may have to revert this
(and the corresponding clang patch) unless we can come up with and
alternative solution.  Do you have any ideas?  Here is the relevant
information from the ABI compatibility report:

--------------------------------------------------------------------------------

class GCOVOptions:

Size of this class has been changed from 9 bytes to 10 bytes.

1) The class has only inline or auto-generated constructors which will be
copied to applications at compile time and will allocate an older memory
layout. Call of any exported method of this class may access a memory
outside the allocated objects or inside the older memory structure and
result in crash or incorrect behavior of applications.

2) The memory layout and size of subclasses will be changed.

--------------------------------------------------------------------------------

Thanks,
Tom

> > 
> >     GCOV: Make the exit block placement from r223193 optional
> >     
> >     By default we want our gcov emission to stay 4.2 compatible, which
> >     means we need to continue emit the exit block last by default. We add
> >     an option to emit it before the body for users that need it.
> > 
> >   llvm/r232443:
> 
> r236304
> 
> > 
> >     llvm-cov: Warn instead of error if a .gcda has arcs from an exit block
> >     
> >     Patch by Vanderson M. Rosario. Thanks!
> > 
> >   clang/r232439:
> 
> r236305
> 
> > 
> >     GCOV: Expose the -coverage-exit-block-before-body flag in clang -cc1
> >     
> >     This exposes the optional exit block placement logic from r232438 as a
> >     clang -cc1 option. There is a test on the llvm side, but there isn't
> >     really a way to inspect the gcov options from clang to test it here as
> >     well.
> 
> -Tom
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