CHECK diff_ failed in custom loss function layer

[harman]

I'm writing a custom loss function in C++ for caffe. I have written a simple test case for this loss function but when I run the tests, I get the following error:

F0704 03:28:29.754256 22013 blob.cpp:145] Check failed: diff_
*** Check failure stack trace: ***
    @     0x7f287f7cc5cd  google::LogMessage::Fail()
    @     0x7f287f7ce433  google::LogMessage::SendToLog()
    @     0x7f287f7cc15b  google::LogMessage::Flush()
    @     0x7f287f7cee1e  google::LogMessageFatal::~LogMessageFatal()
    @     0x7f287ab1555b  caffe::Blob<>::mutable_cpu_diff()
    @           0x50004a  caffe::CustomLossLayerTest_TestRead_Test<>::TestBody()
    @           0x940693  testing::internal::HandleExceptionsInMethodIfSupported<>()
    @           0x939caa  testing::Test::Run()
    @           0x939df8  testing::TestInfo::Run()
    @           0x939ed5  testing::TestCase::Run()
    @           0x93b1af  testing::internal::UnitTestImpl::RunAllTests()
    @           0x93b4d3  testing::UnitTest::Run()
    @           0x46f5fd  main
    @     0x7f2879e49830  __libc_start_main
    @           0x477229  _start
    @              (nil)  (unknown)
Makefile:532: recipe for target 'runtest' failed
make: *** [runtest] Aborted (core dumped)

As of now, I have just written the

Forward_cpu()

method for

Backward_cpu()

I have simply added zeros. Right now i just want to verify that the loss is computed correctly.

Why do i get this error and how do I resolve this ?