third_party/googletest/README.md

### Generic Build Instructions ###

#### Setup ####

To build Google Test and your tests that use it, you need to tell your
build system where to find its headers and source files.  The exact
way to do it depends on which build system you use, and is usually
straightforward.

#### Build ####

Suppose you put Google Test in directory `${GTEST_DIR}`.  To build it,
create a library build target (or a project as called by Visual Studio
and Xcode) to compile

    ${GTEST_DIR}/src/gtest-all.cc

with `${GTEST_DIR}/include` in the system header search path and `${GTEST_DIR}`
in the normal header search path.  Assuming a Linux-like system and gcc,
something like the following will do:

    g++ -isystem ${GTEST_DIR}/include -I${GTEST_DIR} \
        -pthread -c ${GTEST_DIR}/src/gtest-all.cc
    ar -rv libgtest.a gtest-all.o

(We need `-pthread` as Google Test uses threads.)

Next, you should compile your test source file with
`${GTEST_DIR}/include` in the system header search path, and link it
with gtest and any other necessary libraries:

    g++ -isystem ${GTEST_DIR}/include -pthread path/to/your_test.cc libgtest.a \
        -o your_test

As an example, the make/ directory contains a Makefile that you can
use to build Google Test on systems where GNU make is available
(e.g. Linux, Mac OS X, and Cygwin).  It doesn't try to build Google
Test's own tests.  Instead, it just builds the Google Test library and
a sample test.  You can use it as a starting point for your own build
script.

If the default settings are correct for your environment, the
following commands should succeed:

    cd ${GTEST_DIR}/make
    make
    ./sample1_unittest

If you see errors, try to tweak the contents of `make/Makefile` to make
them go away.  There are instructions in `make/Makefile` on how to do
it.

### Using CMake ###

Google Test comes with a CMake build script (
[CMakeLists.txt](CMakeLists.txt)) that can be used on a wide range of platforms ("C" stands for
cross-platform.). If you don't have CMake installed already, you can
download it for free from <http://www.cmake.org/>.

CMake works by generating native makefiles or build projects that can
be used in the compiler environment of your choice.  You can either
build Google Test as a standalone project or it can be incorporated
into an existing CMake build for another project.

#### Standalone CMake Project ####

When building Google Test as a standalone project, the typical
workflow starts with:

    mkdir mybuild       # Create a directory to hold the build output.
    cd mybuild
    cmake ${GTEST_DIR}  # Generate native build scripts.

If you want to build Google Test's samples, you should replace the
last command with

    cmake -Dgtest_build_samples=ON ${GTEST_DIR}

If you are on a \*nix system, you should now see a Makefile in the
current directory.  Just type 'make' to build gtest.

If you use Windows and have Visual Studio installed, a `gtest.sln` file
and several `.vcproj` files will be created.  You can then build them
using Visual Studio.

On Mac OS X with Xcode installed, a `.xcodeproj` file will be generated.

#### Incorporating Into An Existing CMake Project ####

If you want to use gtest in a project which already uses CMake, then a
more robust and flexible approach is to build gtest as part of that
project directly. This is done by making the GoogleTest source code
available to the main build and adding it using CMake's
`add_subdirectory()` command. This has the significant advantage that
the same compiler and linker settings are used between gtest and the
rest of your project, so issues associated with using incompatible
libraries (eg debug/release), etc. are avoided. This is particularly
useful on Windows. Making GoogleTest's source code available to the
main build can be done a few different ways:

* Download the GoogleTest source code manually and place it at a
  known location. This is the least flexible approach and can make
  it more difficult to use with continuous integration systems, etc.
* Embed the GoogleTest source code as a direct copy in the main
  project's source tree. This is often the simplest approach, but is
  also the hardest to keep up to date. Some organizations may not
  permit this method.
* Add GoogleTest as a git submodule or equivalent. This may not
  always be possible or appropriate. Git submodules, for example,
  have their own set of advantages and drawbacks.
* Use CMake to download GoogleTest as part of the build's configure
  step. This is just a little more complex, but doesn't have the
  limitations of the other methods.

The last of the above methods is implemented with a small piece
of CMake code in a separate file (e.g. `CMakeLists.txt.in`) which
is copied to the build area and then invoked as a sub-build
_during the CMake stage_. That directory is then pulled into the
main build with `add_subdirectory()`. For example:

New file `CMakeLists.txt.in`:

    cmake_minimum_required(VERSION 2.8.2)
 
    project(googletest-download NONE)
 
    include(ExternalProject)
    ExternalProject_Add(googletest
      GIT_REPOSITORY    https://github.com/google/googletest.git
      GIT_TAG           master
      SOURCE_DIR        "${CMAKE_BINARY_DIR}/googletest-src"
      BINARY_DIR        "${CMAKE_BINARY_DIR}/googletest-build"
      CONFIGURE_COMMAND ""
      BUILD_COMMAND     ""
      INSTALL_COMMAND   ""
      TEST_COMMAND      ""
    )
    
Existing build's `CMakeLists.txt`:

    # Download and unpack googletest at configure time
    configure_file(CMakeLists.txt.in googletest-download/CMakeLists.txt)
    execute_process(COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}" .
      RESULT_VARIABLE result
      WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/googletest-download )
    if(result)
      message(FATAL_ERROR "CMake step for googletest failed: ${result}")
    endif()
    execute_process(COMMAND ${CMAKE_COMMAND} --build .
      RESULT_VARIABLE result
      WORKING_DIRECTORY ${CMAKE_BINARY_DIR}/googletest-download )
    if(result)
      message(FATAL_ERROR "Build step for googletest failed: ${result}")
    endif()

    # Prevent overriding the parent project's compiler/linker
    # settings on Windows
    set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
    
    # Add googletest directly to our build. This defines
    # the gtest and gtest_main targets.
    add_subdirectory(${CMAKE_BINARY_DIR}/googletest-src
                     ${CMAKE_BINARY_DIR}/googletest-build
                     EXCLUDE_FROM_ALL)

    # The gtest/gtest_main targets carry header search path
    # dependencies automatically when using CMake 2.8.11 or
    # later. Otherwise we have to add them here ourselves.
    if (CMAKE_VERSION VERSION_LESS 2.8.11)
      include_directories("${gtest_SOURCE_DIR}/include")
    endif()

    # Now simply link against gtest or gtest_main as needed. Eg
    add_executable(example example.cpp)
    target_link_libraries(example gtest_main)
    add_test(NAME example_test COMMAND example)

Note that this approach requires CMake 2.8.2 or later due to
its use of the `ExternalProject_Add()` command. The above
technique is discussed in more detail in 
[this separate article](http://crascit.com/2015/07/25/cmake-gtest/)
which also contains a link to a fully generalized implementation
of the technique.

##### Visual Studio Dynamic vs Static Runtimes #####

By default, new Visual Studio projects link the C runtimes dynamically
but Google Test links them statically.
This will generate an error that looks something like the following:
    gtest.lib(gtest-all.obj) : error LNK2038: mismatch detected for 'RuntimeLibrary': value 'MTd_StaticDebug' doesn't match value 'MDd_DynamicDebug' in main.obj

Google Test already has a CMake option for this: `gtest_force_shared_crt`

Enabling this option will make gtest link the runtimes dynamically too,
and match the project in which it is included.

### Legacy Build Scripts ###

Before settling on CMake, we have been providing hand-maintained build
projects/scripts for Visual Studio, Xcode, and Autotools.  While we
continue to provide them for convenience, they are not actively
maintained any more.  We highly recommend that you follow the
instructions in the above sections to integrate Google Test
with your existing build system.

If you still need to use the legacy build scripts, here's how:

The msvc\ folder contains two solutions with Visual C++ projects.
Open the `gtest.sln` or `gtest-md.sln` file using Visual Studio, and you
are ready to build Google Test the same way you build any Visual
Studio project.  Files that have names ending with -md use DLL
versions of Microsoft runtime libraries (the /MD or the /MDd compiler
option).  Files without that suffix use static versions of the runtime
libraries (the /MT or the /MTd option).  Please note that one must use
the same option to compile both gtest and the test code.  If you use
Visual Studio 2005 or above, we recommend the -md version as /MD is
the default for new projects in these versions of Visual Studio.

On Mac OS X, open the `gtest.xcodeproj` in the `xcode/` folder using
Xcode.  Build the "gtest" target.  The universal binary framework will
end up in your selected build directory (selected in the Xcode
"Preferences..." -> "Building" pane and defaults to xcode/build).
Alternatively, at the command line, enter:

    xcodebuild

This will build the "Release" configuration of gtest.framework in your
default build location.  See the "xcodebuild" man page for more
information about building different configurations and building in
different locations.

If you wish to use the Google Test Xcode project with Xcode 4.x and
above, you need to either:

 * update the SDK configuration options in xcode/Config/General.xconfig.
   Comment options `SDKROOT`, `MACOS_DEPLOYMENT_TARGET`, and `GCC_VERSION`. If
   you choose this route you lose the ability to target earlier versions
   of MacOS X.
 * Install an SDK for an earlier version. This doesn't appear to be
   supported by Apple, but has been reported to work
   (http://stackoverflow.com/questions/5378518).

### Tweaking Google Test ###

Google Test can be used in diverse environments.  The default
configuration may not work (or may not work well) out of the box in
some environments.  However, you can easily tweak Google Test by
defining control macros on the compiler command line.  Generally,
these macros are named like `GTEST_XYZ` and you define them to either 1
or 0 to enable or disable a certain feature.

We list the most frequently used macros below.  For a complete list,
see file [include/gtest/internal/gtest-port.h](include/gtest/internal/gtest-port.h).

### Choosing a TR1 Tuple Library ###

Some Google Test features require the C++ Technical Report 1 (TR1)
tuple library, which is not yet available with all compilers.  The
good news is that Google Test implements a subset of TR1 tuple that's
enough for its own need, and will automatically use this when the
compiler doesn't provide TR1 tuple.

Usually you don't need to care about which tuple library Google Test
uses.  However, if your project already uses TR1 tuple, you need to
tell Google Test to use the same TR1 tuple library the rest of your
project uses, or the two tuple implementations will clash.  To do
that, add

    -DGTEST_USE_OWN_TR1_TUPLE=0

to the compiler flags while compiling Google Test and your tests.  If
you want to force Google Test to use its own tuple library, just add

    -DGTEST_USE_OWN_TR1_TUPLE=1

to the compiler flags instead.

If you don't want Google Test to use tuple at all, add

    -DGTEST_HAS_TR1_TUPLE=0

and all features using tuple will be disabled.

### Multi-threaded Tests ###

Google Test is thread-safe where the pthread library is available.
After `#include "gtest/gtest.h"`, you can check the `GTEST_IS_THREADSAFE`
macro to see whether this is the case (yes if the macro is `#defined` to
1, no if it's undefined.).

If Google Test doesn't correctly detect whether pthread is available
in your environment, you can force it with

    -DGTEST_HAS_PTHREAD=1

or

    -DGTEST_HAS_PTHREAD=0

When Google Test uses pthread, you may need to add flags to your
compiler and/or linker to select the pthread library, or you'll get
link errors.  If you use the CMake script or the deprecated Autotools
script, this is taken care of for you.  If you use your own build
script, you'll need to read your compiler and linker's manual to
figure out what flags to add.

### As a Shared Library (DLL) ###

Google Test is compact, so most users can build and link it as a
static library for the simplicity.  You can choose to use Google Test
as a shared library (known as a DLL on Windows) if you prefer.

To compile *gtest* as a shared library, add

    -DGTEST_CREATE_SHARED_LIBRARY=1

to the compiler flags.  You'll also need to tell the linker to produce
a shared library instead - consult your linker's manual for how to do
it.

To compile your *tests* that use the gtest shared library, add

    -DGTEST_LINKED_AS_SHARED_LIBRARY=1

to the compiler flags.

Note: while the above steps aren't technically necessary today when
using some compilers (e.g. GCC), they may become necessary in the
future, if we decide to improve the speed of loading the library (see
<http://gcc.gnu.org/wiki/Visibility> for details).  Therefore you are
recommended to always add the above flags when using Google Test as a
shared library.  Otherwise a future release of Google Test may break
your build script.

### Avoiding Macro Name Clashes ###

In C++, macros don't obey namespaces.  Therefore two libraries that
both define a macro of the same name will clash if you `#include` both
definitions.  In case a Google Test macro clashes with another
library, you can force Google Test to rename its macro to avoid the
conflict.

Specifically, if both Google Test and some other code define macro
FOO, you can add

    -DGTEST_DONT_DEFINE_FOO=1

to the compiler flags to tell Google Test to change the macro's name
from `FOO` to `GTEST_FOO`.  Currently `FOO` can be `FAIL`, `SUCCEED`,
or `TEST`.  For example, with `-DGTEST_DONT_DEFINE_TEST=1`, you'll
need to write

    GTEST_TEST(SomeTest, DoesThis) { ... }

instead of

    TEST(SomeTest, DoesThis) { ... }

in order to define a test.