CMake无法隐藏符号但Android.mk可行，求助解决-fvisibility=hidden失效问题

问题现象 #

在Android NDK环境中，使用CMake配置set(CMAKE_CXX_VISIBILITY_PRESET hidden)，或给target添加-fvisibility=hidden编译选项，均无法实现符号隐藏。但-Wl,-Bsymbolic等其他编译选项可正常生效，编译宏也能正确传递。相同NDK环境下，用Android.mk配置-fvisibility=hidden却能成功隐藏符号。

相关配置与输出 #

CMakeLists.txt内容 #

cmake_minimum_required(VERSION 3.20)
project(multp)

message("generator: ${CMAKE_GENERATOR_PLATFORM}")
message("CMAKE_SIZEOF_VOID_P is ${CMAKE_SIZEOF_VOID_P}")
message("CMAKE_SYSTEM_NAME is ${CMAKE_SYSTEM_NAME}")
enable_testing()
list(APPEND CMAKE_MODULE_PATH "${CMAKE_SOURCE_DIR}/cmake")
set(CMAKE_C_VISIBILITY_PRESET hidden)
set(CMAKE_CXX_VISIBILITY_PRESET hidden)
include(build/cmake/cmake-definition.cmake)
include(build/cmake/Format.cmake)
add_subdirectory(vendors/openssl/1.1.1s)
add_subdirectory(vendors/rapidjson)
add_subdirectory(vendors/gmssl)
add_subdirectory(platform/multp)

target_link_libraries(multp PUBLIC  gmssl rapidjson)
target_compile_options(multp PRIVATE "-Wl,--exclude-libs,ALL" "-Wl,-Bsymbolic" "-fvisibility=hidden")
target_link_options(multp PRIVATE "-Wl,--exclude-libs,ALL" "-Wl,-Bsymbolic" "-fvisibility=hidden")

编译命令行 #

cmake -DANDROID_ABI=arm64-v8a -DHDMW_CODEC_ENABLED=TRUE -DANDROID_PLATFORM=android-23 -DANDROID_STL=c++_shared -DCMAKE_BUILD_TYPE=Release -DCMAKE_TOOLCHAIN_FILE=G:\Android\SDK\ndk\23.1.7779620\build\cmake\android.toolchain.cmake -DCMAKE_SYSTEM_NAME=Android -B ./cmake-android -S . -G Ninja

Android.mk内容 #

APP_STL        := c++_shared

APP_CFLAGS     += -O3 -DANDROID \
                  -Werror=return-type \
                  -Werror=implicit-int \
                  -Werror=incompatible-pointer-types \
                  -Werror=shadow \
                  -Werror=return-stack-address \
                  -Werror=uninitialized \
                  -Werror=format \
                  -Werror=sign-compare \
                  -Werror=int-conversion \
                  -Werror=inconsistent-missing-override \
                  -Werror=implicit-function-declaration \
                  -fvisibility=hidden

ifeq ($(NDK_DEBUG),1)
APP_CFLAGS     += -fsanitize=address \
                  -fno-omit-frame-pointer
APP_LDFLAGS    := -fsanitize=address
endif

ifdef BUILD_VERSION
APP_CFLAGS     += -DBUILD_VERSION=$(BUILD_VERSION)
endif

APP_CPPFLAGS   := $(APP_CFLAGS) -fexceptions -std=c++14

APP_PLATFORM   := android-21

#set as the ndk-build option,
#like this: ndk-build NDK_DEBUG=0/1
#0:release, 1:debug
#APP_OPTIM     := release

#the new ndk not support this setting.
#NDK_TOOLCHAIN_VERSION := 4.9

APP_ABI        := armeabi-v7a arm64-v8a

LOCAL_C_INCLUDES += \
                    $(LOCAL_PATH)/src \
                    $(LOCAL_PATH)/h \
                    $(LOCAL_PATH)/../../vendors/gmssl/include \
                    $(LOCAL_PATH)/../../vendors/openssl/1.1.1s/include

LOCAL_CFLAGS := $(MY_COMMON_DEFS)
LOCAL_CPPFLAGS += -frtti -fexceptions

LOCAL_LDLIBS += -lz -ldl -llog
LOCAL_STATIC_LIBRARIES := libgmssl \
                          libssl \
                          libcrypto 

nm命令输出 #

work-dir> nm -CD libmultp.so
                 U __cmsg_nxthdr
                 U __cxa_allocate_exception
                 U __cxa_atexit
                 U __cxa_begin_catch
                 U __cxa_end_catch
                 U __cxa_finalize
                 U __cxa_free_exception
                 U __cxa_pure_virtual
                 U __cxa_rethrow
                 U __cxa_throw
                 U __errno
                 U __FD_ISSET_chk
                 U __FD_SET_chk
                 U __gxx_personality_v0
                 U __register_atfork
                 U __sF
00000000001cfb9c T crc32_fast(void const*, unsigned long, unsigned int)
0000000000154b90 W void TrimString<CCmIsSpace>(CCmString&, CCmIsSpace)
000000000014bda0 T CalcCRC16_m(unsigned short&, CCmMessageBlock&, unsigned int)
00000000001d0224 T crc32_1byte(void const*, unsigned long, unsigned int)
00000000001403ac T init_config(char const*)
000000000015648c W void LTrimString<CCmIsSpace>(CCmString&, CCmIsSpace)
0000000000156534 W void RTrimString<CCmIsSpace>(CCmString&, CCmIsSpace)
000000000013fb10 T trim_string(char*)
00000000001d04bc T crc32_4bytes(void const*, unsigned long, unsigned int)
00000000001d05fc T crc32_8bytes(void const*, unsigned long, unsigned int)
0000000000141664 T get_local_ip()
00000000001b0e08 T ipv4_enabled()
00000000001b0db8 T ipv6_enabled()
0000000000141308 T resolve_2_ip(char*, char*)
00000000001d09ec T crc32_16bytes(void const*, unsigned long, unsigned int)
00000000001d00d4 T crc32_bitwise(void const*, unsigned long, unsigned int)
00000000001d0fc4 T crc32_combine(unsigned int, unsigned int, unsigned long)

排查与解决方法 #

1. 检查CMAKE_CXX_VISIBILITY_PRESET生效时机
   CMAKE_CXX_VISIBILITY_PRESET必须在add_subdirectory或add_library/add_executable之前设置才会对目标生效。当前配置中虽已提前设置，但需确认build/cmake/cmake-definition.cmake是否覆盖了该变量，若有覆盖会导致原配置失效。

2. 修正选项位置错误
   target_compile_options中不应包含-Wl,--exclude-libs,ALL和-Wl,-Bsymbolic这类链接选项，需将其移至target_link_options，仅保留编译相关选项：

   target_compile_options(multp PRIVATE "-fvisibility=hidden")
   target_link_options(multp PRIVATE "-Wl,--exclude-libs,ALL" "-Wl,-Bsymbolic")
   

3. 补充C++符号隐藏辅助配置
   对于C++代码，需额外启用内联函数符号隐藏：

   set(CMAKE_VISIBILITY_INLINES_HIDDEN ON)
   

   该配置确保内联函数的符号不会暴露到最终SO中。

4. 验证编译选项是否实际传递
   执行编译命令时添加VERBOSE=1，查看实际编译参数中是否包含-fvisibility=hidden：

   cmake --build ./cmake-android -- VERBOSE=1
   

   若未找到该选项，说明CMake配置被其他逻辑覆盖，需检查目标的编译选项优先级。

5. 处理模板函数符号
   nm输出中的TrimString<CCmIsSpace>等模板符号（标记为W），需添加额外编译选项处理：

   target_compile_options(multp PRIVATE "-fvisibility-inlines-hidden")
   

   或在模板声明前手动添加__attribute__((visibility("hidden")))，强制隐藏模板实例化符号。

6. 排查第三方依赖符号传递
   链接的gmssl、openssl等静态库若未启用符号隐藏，会将自身符号暴露到最终SO中。可尝试给第三方库也添加符号隐藏配置，或确认-Wl,--exclude-libs,ALL是否生效，彻底排除静态库的符号。

内容的提问来源于stack exchange，提问作者qian