# Libraries:
  C++17
  boost (spirit, program option, unit_test_framework)
  libedit / readline

# Machine Resources - Building Hisqry:
  FreeBSD 13.0-RELEASE i386 with 2GB RAM
    - peak memory usage at ~1.5GB with clang10
  FreeBSD 12.2-RELEASE amd64 with 2GB RAM
    - peak memory usage at ~2GB with clang10
  NetBSD 9.1 i386 with 3GB RAM
    - peak memory usage at ~1.5GB with clang10
    - peak memory usage at ~2.3GB with gcc10
  Linux Ubuntu 21.04 amd64 with 4GB RAM
    - peak memory usage at ~3GB with gcc10

src/single - BSD Make / GNU Makefile:
  Single build allows to compile and link all source files.
This only requires ~100 MB of disk space.
  % cd src/single
  % make
  % ./hisqry.pm

CMake
  CMake builds hisqry and unittest.  This uses shared libraries and loading of
unittest cases seems linker dependent.  llvm's ld runs test cases okay
but not GNU ld.  Object files are large and require ~5GB disk space.
  % mkdir build
  % cd build
  % cmake ..
  % cmake --build . -j 5
  % ./src/hisqry/hisqry.pm

BSD Make
  The other Makefiles are BSD Makefiles.  These are use for primary
development and have extra debug and sanity check flags are enabled.
These use static libraries.  There are extra debug helper programs
and targets for debugging and testing.
  Top level Makefile is used most often as a trigger.  This builds hisqry
and unittest.
  % make

# Machine Resources - Building Unit Tests:

Machine Resources:
  FreeBSD 12.2/13.0-RELEASE i386
    with 4GB memory
    with 2GB Memory + 2GB swap for unittests
    - peak memory usage at ~3GB with clang10

BSD Make:
  BSD Make is one of the primary development tool used.
  % cd src/hisqry
  % make -j 5

CMake
  Same as above.
  % cd build
  % cmake ..
  % cmake --build . -j 5
  % ./test/boost/hisqry.pm

Directory Hierarchy
  src/single - hisqry program with a single compilation command
  src/hisqry - hisqry program with modules - same as above
  src/type - hisqry base types and exceptions
  src/db - an implementation of database - 'type' is the only dependency
  src/opr - an abstraction layer of SQL commands into C++ classes
  src/sql - SQL parser that generates opr classes
  src/eng - engine that ties sql parser, opr classes, and db implementation
  test/boost - unit test cases with Boost Test Framework