Problem: Coverage with coveralls not working

Solution: Enable coveralls for one linux build target and fix coveralls
configuration.

.travis.yml

@@ -23,6 +23,21 @@ matrix:
     # GCC on Linux
     ##########################################################
 
+    # Coverage, GCC 7, draft enabled, latest libzmq (default)
+    - os: linux
+      before_install:
+        - pip install --user cpp-coveralls
+      addons:
+        apt:
+          sources:
+            - ubuntu-toolchain-r-test
+          packages:
+            - g++-7
+      env:
+        - MATRIX_EVAL="CC=gcc-7 && CXX=g++-7" ENABLE_DRAFTS=ON COVERAGE=ON
+      after_success:
+        - coveralls -r . -E ".*external.*" -E ".*CMakeFiles.*" -E ".*tests/" -E ".*demo/" -E ".*libzmq.*/" -b cppzmq-build --gcov-options '\-lp'
+
     # GCC default, draft disabled,  older libzmq with pkg-config
     - os: linux
       env: ZMQ_VERSION=4.2.0 BUILD_TYPE=pkgconfig
@@ -51,6 +66,7 @@ matrix:
             - g++-7
       env:
         - MATRIX_EVAL="CC=gcc-7 && CXX=g++-7" ENABLE_DRAFTS=ON
+
   # - env: BUILD_TYPE=cmake DO_CLANG_FORMAT_CHECK=1 CLANG_FORMAT=/usr/local/clang-5.0.0/bin/clang-format
     # os: linux
     # addons:
@@ -60,14 +76,9 @@ matrix:
       # packages:
         # - clang-5.0
 
-before_install:
-  - if [ "$TRAVIS_OS_NAME" = "linux" ]; then pip install --user cpp-coveralls; fi
-
 # Build and check this project
 script:
   - eval "${MATRIX_EVAL}"
   - cmake --version
   - ./ci_build.sh
 
-after_success:
-  - if [ "$TRAVIS_OS_NAME" = "linux" ]; then coveralls --root . -E ".*external.*" -E ".*CMakeFiles.*" -E ".*tests/" -E ".*demo/" -E ".*libzmq/"; fi

ci_build.sh

@@ -6,6 +6,7 @@ set -e
 BUILD_TYPE=${BUILD_TYPE:-cmake}
 ZMQ_VERSION=${ZMQ_VERSION:-4.2.5}
 ENABLE_DRAFTS=${ENABLE_DRAFTS:-OFF}
+COVERAGE=${COVERAGE:-OFF}
 LIBZMQ=${PWD}/libzmq-build
 CPPZMQ=${PWD}/cppzmq-build
 # Travis machines have 2 cores
@@ -37,7 +38,8 @@ libzmq_install() {
 cppzmq_build() {
     pushd .
     CMAKE_PREFIX_PATH=${LIBZMQ} \
-    cmake -H. -B${CPPZMQ} -DENABLE_DRAFTS=${ENABLE_DRAFTS}
+    cmake -H. -B${CPPZMQ} -DENABLE_DRAFTS=${ENABLE_DRAFTS} \
+                          -DCOVERAGE=${COVERAGE}
     cmake --build ${CPPZMQ} -- -j${JOBS}
     popd
 }

tests/CMakeLists.txt

@@ -9,11 +9,6 @@ set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_LIBDIR})
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_LIBDIR})
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/${CMAKE_INSTALL_BINDIR})
 
-# we use this to get code coverage
-if(CMAKE_CXX_COMPILER_ID MATCHES GNU)
-    set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -fprofile-arcs -ftest-coverage")
-endif()
-
 include(cmake/googletest.cmake)
 fetch_googletest(
     ${PROJECT_SOURCE_DIR}/cmake
@@ -32,10 +27,17 @@ add_executable(
 
 target_link_libraries(
     unit_tests
-    gtest_main
-    cppzmq
+    PRIVATE gtest_main
+    PRIVATE cppzmq
     )
 
+OPTION (COVERAGE "Enable gcda file generation needed by lcov" OFF)
+
+if (COVERAGE)
+    target_compile_options(unit_tests PRIVATE --coverage)
+    target_link_libraries(unit_tests PRIVATE --coverage)
+endif()
+
 add_test(
   NAME
     unit