Include stddef.h as well

[dustalov]

Hello! I tried to compile Faiss on Fedora 24 with GCC 6.3.1, but the compilation, unfortunately, failed.

$ make
g++ -fPIC -m64 -Wall -g -O3  -msse4 -mpopcnt -fopenmp -Wno-sign-compare -Dnullptr=NULL -Doverride= -fopenmp -c hamming.cpp -o hamming.o  
<command-line>:0:9: error: 'NULL' was not declared in this scope
<command-line>:0:9: error: 'NULL' was not declared in this scope

I found two options for addressing this problem: to either substitute NULL with the “magical” 0 or to explicitly include stddef.h via command-line. I believe the latter option is more portable. It successfully worked for me on both Fedora 24 and CentOS 7 (GCC 4.8.5).

The present pull request contains the above-mentioned change to makefile.inc.Linux.

[mdouze]

Hi,

Could you try by removing -Dnullptr=NULL flag?

[dustalov]

Removing -Dnullptr=NULL works perfectly on GCC 6.3.1, but fails on GCC 4.8.5.

$ make
g++ -fPIC -m64 -Wall -g -O3  -msse4 -mpopcnt -fopenmp -Wno-sign-compare -Doverride= -fopenmp -c hamming.cpp -o hamming.o  
In file included from hamming.h:33:0,
                 from hamming.cpp:28:
Heap.h:191:9: warning: identifier 'nullptr' is a keyword in C++11 [-Wc++0x-compat]
         const typename C::T * x = nullptr,
         ^
Heap.h:191:35: error: 'nullptr' was not declared in this scope
         const typename C::T * x = nullptr,

[mdouze]

Thanks for the report.

I added an entry in the troubleshooting section:

https://github.com/facebookresearch/faiss/wiki/Troubleshooting#nullnullptr0