Re: Compiling for FreeBSD, trouble in buffer.c

[Willem Jan Withagen <wjw@digiware.nl>]

I have a failure in:
  ./unittest_erasure_code_shec_arguments
All tests befor this PASS. (other than rbd which is disabled to
the time being)

Which I traceback to code in ErasureCodeShec.cc
Line 218:
	unsigned blocksize = (*chunks.begin()).second.length();
After a few iterations I get a "negative" blocksize, which causes
allocations further on to really thrash the system out of swap.

At first I expected it could be due to a Clang typecasting problem.
But after more debugging I found the following in
buffer.h
     unsigned length() const {
#if 0
       // DEBUG: verify _len
       unsigned len = 0;
       for (std::list<ptr>::const_iterator it = _buffers.begin();
            it != _buffers.end();
            it++) {
         len += (*it).length();
       }
       assert(len == _len);
#endif
       return _len;
     }

Which suggests that debugging was needed at this point earlier in life.
If I enable this debug block, I do get the assert affected.

Now the next question is why? Given the debug snippet it needed 
analyzing before.
And the derived question then is:
	What is the easiest path to find out what is actually wrong here.

All suggestions welcome.

--WjW