error: statement with no effect [-Werror=unused-value]

　　完整錯誤如下：

make[1]: 進入目錄“/home/quantum6/freeswitch/freeswitch-1.10.3”
  CC       src/libfreeswitch_la-switch_core_cert.lo
In file included from ./src/include/switch_ssl.h:39:0,
                 from src/switch_core_cert.c:33:
src/switch_core_cert.c: In function ‘switch_ssl_init_ssl_locks’:
/home/quantum6/build_libs/include/openssl/crypto.h:235:57: error: statement with no effect [-Werror=unused-value]
 #  define CRYPTO_THREADID_set_callback(threadid_func)   (0)
                                                         ^
src/switch_core_cert.c:72:3: note: in expansion of macro ‘CRYPTO_THREADID_set_callback’
   CRYPTO_THREADID_set_callback(switch_ssl_ssl_thread_id);
   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
cc1: all warnings being treated as errors
Makefile:2269: recipe for target 'src/libfreeswitch_la-switch_core_cert.lo' failed
make[1]: *** [src/libfreeswitch_la-switch_core_cert.lo] Error 1

　　解決辦法，增加 -Wno-error=unused-value：

./configure \
    --prefix=${BUILD_LIBS} \
    --disable-core-libedit-support \
     CFLAGS="-I${BUILD_LIBS}/include -Wno-error=unused-value" \
    LDFLAGS=-L${BUILD_LIBS}/lib


# 這個參數無效。
#    --disable-werror