Oh yes I did build master (c44626956), not the stable 0.4.0.
I tried again with 0.4.0, and yes, libATen.so replaced the libcaffe2*  :

include/
libATen.so
libnccl.so
libnccl.so.1
libshm.so
THCUNN.h
THNN.h
torch_shm_manager

So, since I’m trying to implement a function in C/C++, I’m confused about which library I should use.
Right now I use torch, meaning I #include <TH/TH.h> and link against libTH.so (built with torch7 on its own)
I see that ATen is “new” and that it is a C++11 wrapper of pytorch and torch functions.
Should I use ATen then ? But ATen also contains the TH.h header and the torch code it seems like.
What is the difference between ATen and torch ?
If I understand correctly :
torch : the lib is called libTH.so
pytorch 0.4.0  : the lib is called libATen.so
pytorch > 0.4.0 : the libs will be called libcaffe2*
I read about Caffe2 on the blogpost :

On the backend side of things, PyTorch will see some changes, which might affect user-written C and C++ extensions. We are replacing (or refactoring) the backend ATen library to incorporate features and optimizations from Caffe2.

Will Caffe2 still use the same functions as in ATen and torch (e.g. THFloatTensor_newWithSize1d()) ?
Or will I have to change the code completely ?