Force _GNU_SOURCE if glibc is used.

CMakeLists.txt

@@ -18,6 +18,16 @@ find_package(ament_cmake_ros REQUIRED)
 
 ament_python_install_package(${PROJECT_NAME})
 
+if(UNIX AND NOT APPLE)
+  include(cmake/check_c_compiler_uses_glibc.cmake)
+  check_c_compiler_uses_glibc(USES_GLIBC)
+  if(USES_GLIBC)
+    # Ensure GNU extended libc API is used, as C++ test code will.
+    # See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=2082.
+    add_definitions(-D_GNU_SOURCE)
+  endif()
+endif()
+
 if(NOT WIN32)
   add_compile_options(-Wall -Wextra -Wpedantic)
 endif()

cmake/check_c_compiler_uses_glibc.cmake

@@ -0,0 +1,36 @@
+# Copyright 2020 Open Source Robotics Foundation, Inc.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+#
+# Checks if the C compiler uses glibc.
+#
+# @private
+#
+function(check_c_compiler_uses_glibc result_variable)
+  include(CheckCSourceCompiles)
+
+  set(GLIBC_TEST_CODE [====[
+    #include <execinfo.h>
+
+    int main() {
+      void * buffer[1];
+      int size = sizeof(buffer) / sizeof(void *);
+      backtrace(&buffer, size);
+      return 0;
+    }
+  ]====])
+
+  check_c_source_compiles("${GLIBC_TEST_CODE}" ${result_variable})
+  set(${result_variable} ${result_variable} PARENT_SCOPE)
+endfunction()

src/process.c

@@ -17,7 +17,6 @@ extern "C"
 {
 #endif
 
-#define _GNU_SOURCE
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>