Nhse d30 eldb275

[martinsumner]

The process for installing eleveldb is as follows:

• rebar.config has a pre-hook to run the Makefile in c_src

  eleveldb/rebar.config

  Lines 33 to 34 in 251f432

  	{pre_hooks, [{'get-deps', "make -C c_src get-deps"},
  	{compile, "make -C c_src compile"}]}.

  for get-deps and compile
• this Makefile determines some environment variables, in particular FLAGS to instruct future downstream compilations to refer to c_src/system/lib and c_src/system/include where the snappy compression code will be held
• the Makefile will then clone leveldb and fetch the required version of snappy from github as part of the get_deps stage.
• in the compile stage, initially Snappy is compiled, into the c_src/systerm directory

  eleveldb/c_src/Makefile

  Lines 36 to 43 in 251f432

  	mkdir build && cd build && \
  	mkdir -p $(BASEDIR)/system && \
  	cmake -D SNAPPY_BUILD_TESTS=0 -D SNAPPY_BUILD_BENCHMARKS=0 \
  	-D CMAKE_INSTALL_PREFIX=$(BASEDIR)/system \
  	..; \
  	fi && \
  	make && make install)
  	mv system/lib64 system/lib || true

• once snappy has been compiled and moved, there is a call to make leveldb
• the leveldb Makefile uses the leveldb/build_detect_platform script to create a build_config.mk to be used in this make process - https://github.com/nhs-riak/leveldb/blob/2fd90c712af1ac9609ef9c1adba98814fb6751ef/Makefile#L18-L23
• the build_detect_platform sets flags based on the OS https://github.com/nhs-riak/leveldb/blob/2fd90c712af1ac9609ef9c1adba98814fb6751ef/build_detect_platform#L63
• the build_detect_platform then sets further flags based on the availability of features, including the installation of snappy. The installation of snappy is detected by compiling some code which includes snappy.h and confirming the compilation has an exit code of 0 https://github.com/nhs-riak/leveldb/blob/2fd90c712af1ac9609ef9c1adba98814fb6751ef/build_detect_platform#L171-L175
• the build_detect_platform script will also detect the presence of leveldb_ee (legacy enterprise version) https://github.com/nhs-riak/leveldb/blob/2fd90c712af1ac9609ef9c1adba98814fb6751ef/build_detect_platform#L135-L139 which should be present due to the of leveldb in .gitmodules as a submodule
• with the build_config.mk file complete and included, the Makefile will then make leveldb using https://github.com/nhs-riak/leveldb/blob/2fd90c712af1ac9609ef9c1adba98814fb6751ef/Makefile#L86
• once this stage is complete, the pre-hook is done, and so eleveldb is compiled using the post provider_hook

  eleveldb/rebar.config

  Lines 7 to 16 in 251f432

  	{provider_hooks,
  	[
  	{post,
  	[
  	{compile, {pc, compile}},
  	{clean, {pc, clean}}
  	]
  	}
  	]
  	}.

• flags for this stage of compilation are generated using rebar.config port_env which are supplemented with OS-specific flags by running the rebar.config.script

The issues this PR addresses are:

• a failure to export the FLAGS from eleveldb/c_src/Makefile means that those flags were not set for downstream Makefiles, and so the test for snappy presence would not compile due to the absence of the include directives in the CFLAGS
• on OSX snappy would silently fail to compile due to a requirement to enforce support for at least the c++11 standard. Fixing this requires changes to both the OS-specific setting in build_detect_platform (for compiling snappy/leveldb) and the rebar.config.script (for compiling eleveldb)
• snappy will no longer compile on OSX 10.8, as there is no intention to build portable packages for OSX, the OSX min version is instead defaulted to the current version (avoiding warnings)

[martinsumner]

Depends on nhs-riak/leveldb#1

[martinsumner]

Allows for merge of test nhs-riak/riak_test#2

[martinsumner]

Resolution to basho#275. Corrected resolution to basho#273

[martinsumner]

As an aside there are issues with snappy 1.1.10 in OSX, so that release will not work:

snappy-1.1.10/snappy.cc:1293:37: error: comparison of integers of different signs: 'unsigned long' and 'ptrdiff_t' (aka 'long') [-Werror,-Wsign-compare]
             (op + deferred_length) < op_limit_min_slop);

The same errors appear to be warnings on Ubuntu, so compile will complete.