Crashes with unittest_dencoder

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

Any hints on what changes in the current code generates the illegal
memaccess in the trace below?

Lots of tests fail, and I guess that mst have to do with this.

--WjW

Program received signal SIGSEGV, Segmentation fault.
0x00000008025e693e in std::__1::__atomic_base<unsigned long,
true>::fetch_add (this=0x108803637688,
    __op=1, __m=std::__1::memory_order_seq_cst) at
/usr/include/c++/v1/atomic:980
980             {return __c11_atomic_fetch_add(&this->__a_, __op, __m);}
(gdb) bt
#0  0x00000008025e693e in std::__1::__atomic_base<unsigned long,
true>::fetch_add (this=0x108803637688,
    __op=1, __m=std::__1::memory_order_seq_cst) at
/usr/include/c++/v1/atomic:980
#1  std::__1::__atomic_base<unsigned long, true>::operator+=
(this=0x108803637688, __op=1)
    at /usr/include/c++/v1/atomic:1025
#2  mempool::pool_t::adjust_count (this=0x108803637680, items=1, bytes=42)
    at /home/jenkins/workspace/ceph-master/src/common/mempool.cc:85
#3  0x00000008024f1bfb in ceph::buffer::raw::reassign_to_mempool
(this=0x1076130, pool=-1)
    at /home/jenkins/workspace/ceph-master/src/common/buffer.cc:196
#4  0x00000008024e1b19 in ceph::buffer::list::reserve
(this=0x7fffffffd040, prealloc=42)
    at /home/jenkins/workspace/ceph-master/src/common/buffer.cc:1772
#5  0x00000000004d0ad5 in ceph::buffer::list::list (this=0x7fffffffd040,
prealloc=42)
    at /home/jenkins/workspace/ceph-master/src/include/buffer.h:662
#6  0x00000000004b4114 in Legacy::encode_n (n=42, segments=...)
    at /home/jenkins/workspace/ceph-master/src/test/test_denc.cc:610
#7  0x00000000004b4d22 in
denc_no_copy_if_segmented_and_lengthy_Test::TestBody (this=0x1068070)
    at /home/jenkins/workspace/ceph-master/src/test/test_denc.cc:633
#8  0x00000000005ea62e in
testing::internal::HandleSehExceptionsInMethodIfSupported<testing::Test,
void> (
    object=0x1068070, method=&virtual testing::Test::TestBody(),
location=0x6156ee "the test body")
    at
/home/jenkins/workspace/ceph-master/src/googletest/googletest/src/gtest.cc:2402
#9  0x00000000005ccabb in
testing::internal::HandleExceptionsInMethodIfSupported<testing::Test,
void> (
    object=0x1068070, method=&virtual testing::Test::TestBody(),
location=0x6156ee "the test body")
    at
/home/jenkins/workspace/ceph-master/src/googletest/googletest/src/gtest.cc:2438
#10 0x00000000005885c6 in testing::Test::Run (this=0x1068070)
    at
/home/jenkins/workspace/ceph-master/src/googletest/googletest/src/gtest.cc:2474
#11 0x000000000058ad0d in testing::TestInfo::Run (this=0x106edd0)
    at
/home/jenkins/workspace/ceph-master/src/googletest/googletest/src/gtest.cc:2656
#12 0x000000000058bfcc in testing::TestCase::Run (this=0x106e0d0)
    at
/home/jenkins/workspace/ceph-master/src/googletest/googletest/src/gtest.cc:2774
#13 0x00000000005a2e8c in testing::internal::UnitTestImpl::RunAllTests
(this=0x1072000)
    at
/home/jenkins/workspace/ceph-master/src/googletest/googletest/src/gtest.cc:4649
#14 0x00000000005ed4be in
testing::internal::HandleSehExceptionsInMethodIfSupported<testing::internal::UnitTestImpl,
bool> (object=0x1072000,
    method=(bool
(testing::internal::UnitTestImpl::*)(testing::internal::UnitTestImpl *
const)) 0x5a2af0 <testing::internal::UnitTestImpl::RunAllTests()>,
    location=0x615d71 "auxiliary test code (environments or event
listeners)")
    at
/home/jenkins/workspace/ceph-master/src/googletest/googletest/src/gtest.cc:2402