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Using GoogleTest from various build systems

GoogleTest comes with pkg-config files that can be used to determine all necessary flags for compiling and linking to GoogleTest (and GoogleMock). Pkg-config is a standardised plain-text format containing

the includedir (-I) path
necessary macro (-D) definitions
further required flags (-pthread)
the library (-L) path
the library (-l) to link to

All current build systems support pkg-config in one way or another. For all examples here we assume you want to compile the sample samples/sample3_unittest.cc.

CMake

Using pkg-config in CMake is fairly easy:

cmake_minimum_required(VERSION 3.0)

cmake_policy(SET CMP0048 NEW)
project(my_gtest_pkgconfig VERSION 0.0.1 LANGUAGES CXX)

find_package(PkgConfig)
pkg_search_module(GTEST REQUIRED gtest_main)

add_executable(testapp samples/sample3_unittest.cc)
target_link_libraries(testapp ${GTEST_LDFLAGS})
target_compile_options(testapp PUBLIC ${GTEST_CFLAGS})

include(CTest)
add_test(first_and_only_test testapp)

It is generally recommended that you use target_compile_options + _CFLAGS over target_include_directories + _INCLUDE_DIRS as the former includes not just -I flags (GoogleTest might require a macro indicating to internal headers that all libraries have been compiled with threading enabled. In addition, GoogleTest might also require -pthread in the compiling step, and as such splitting the pkg-config Cflags variable into include dirs and macros for target_compile_definitions() might still miss this). The same recommendation goes for using _LDFLAGS over the more commonplace _LIBRARIES, which happens to discard -L flags and -pthread.

Autotools

Finding GoogleTest in Autoconf and using it from Automake is also fairly easy:

In your configure.ac:

AC_PREREQ([2.69])
AC_INIT([my_gtest_pkgconfig], [0.0.1])
AC_CONFIG_SRCDIR([samples/sample3_unittest.cc])
AC_PROG_CXX

PKG_CHECK_MODULES([GTEST], [gtest_main])

AM_INIT_AUTOMAKE([foreign subdir-objects])
AC_CONFIG_FILES([Makefile])
AC_OUTPUT

and in your Makefile.am:

check_PROGRAMS = testapp
TESTS = $(check_PROGRAMS)

testapp_SOURCES = samples/sample3_unittest.cc
testapp_CXXFLAGS = $(GTEST_CFLAGS)
testapp_LDADD = $(GTEST_LIBS)

Meson

Meson natively uses pkgconfig to query dependencies:

project('my_gtest_pkgconfig', 'cpp', version : '0.0.1')

gtest_dep = dependency('gtest_main')

testapp = executable(
  'testapp',
  files(['samples/sample3_unittest.cc']),
  dependencies : gtest_dep,
  install : false)

test('first_and_only_test', testapp)

Plain Makefiles

Since pkg-config is a small Unix command-line utility, it can be used in handwritten Makefiles too:

GTEST_CFLAGS = `pkg-config --cflags gtest_main`
GTEST_LIBS = `pkg-config --libs gtest_main`

.PHONY: tests all

tests: all
  ./testapp

all: testapp

testapp: testapp.o
  $(CXX) $(CXXFLAGS) $(LDFLAGS) $< -o $@ $(GTEST_LIBS)

testapp.o: samples/sample3_unittest.cc
  $(CXX) $(CPPFLAGS) $(CXXFLAGS) $< -c -o $@ $(GTEST_CFLAGS)

Help! pkg-config can't find GoogleTest!

Let's say you have a CMakeLists.txt along the lines of the one in this tutorial and you try to run cmake. It is very possible that you get a failure along the lines of:

-- Checking for one of the modules 'gtest_main'
CMake Error at /usr/share/cmake/Modules/FindPkgConfig.cmake:640 (message):
  None of the required 'gtest_main' found

These failures are common if you installed GoogleTest yourself and have not sourced it from a distro or other package manager. If so, you need to tell pkg-config where it can find the .pc files containing the information. Say you installed GoogleTest to /usr/local, then it might be that the .pc files are installed under /usr/local/lib64/pkgconfig. If you set

export PKG_CONFIG_PATH=/usr/local/lib64/pkgconfig

pkg-config will also try to look in PKG_CONFIG_PATH to find gtest_main.pc.

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