-check_decl(pipe2 unistd.h)
-check_decl(SOCK_NONBLOCK sys/socket.h)
-check_decl(SOCK_CLOEXEC sys/socket.h)
-check_header(sys/wait.h)
-check_decl(waitid sys/wait.h)
+add_definitions(-D_GNU_SOURCE)
+set(CMAKE_REQUIRED_DEFINITIONS -D_GNU_SOURCE)
+check_symbol(pipe2 unistd.h)
+check_symbol(SOCK_NONBLOCK sys/socket.h)
+check_symbol(SOCK_CLOEXEC sys/socket.h)
+check_include(sys/wait.h)
+check_symbol(waitid sys/wait.h)