交叉编译Rust到Android时链接器无法找到静态C库符号

问题现象 #

链接阶段出现如下错误：

ld: error: undefined symbol: espeak_Initialize
>>> referenced by lib.rs:108 (packages/espeak/src/lib.rs:108)
>>>               /target/x86_64-linux-android/debug/deps/oratio_espeak-6fba08adc959e6d8.3x6nmh9h9fre8r93.rcgu.o:(oratio_espeak::initialize::h403ba8dd7c5de0ec)
clang140: error: linker command failed with exit code 1 (use -v to see invocation)

已验证的关键信息 #

• 链接器能正确定位到库：修改-L/-l参数会触发“无法找到库”的错误，说明路径配置无误
• 静态库确实包含目标符号：

$ nm libespeak-ng.a | grep espeak_Initialize
0000000000000000 T espeak_Initialize

$ objdump -f libespeak-ng.a
libespeak-ng.a(libespeak_ng_la-case.o): file format elf64-x86-64
architecture: x86_64
start address: 0x0000000000000000

[repeat for all object files...]

交叉编译espeak-ng的命令 #

使用Android NDK编译静态库的命令如下：

PATH=$NDK_HOME/toolchains/llvm/prebuilt/darwin-x86_64/bin:$PATH
CC="x86_64-linux-android33-clang"
CXX="x86_64-linux-android33-clang++"

./autogen.sh
./configure --host=aarch64-apple-darwin --target=x86_64-linux-android
make

构建与链接参数 #

构建命令 #

$ cross test --target x86_64-linux-android --config target.x86_64-linux-android.linker="'/android-ndk/bin/x86_64-linux-android33-clang'" --config target.x86_64-linux-android.ar="'/android-ndk/bin/x86_64-linux-android-ar'"

注：也尝试过不带--config参数的情况，此时链接器变为cc，但错误相同。

链接器完整调用参数（简化后） #

LC_ALL="C"
PATH="/Users/arthur/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-unknown-linux-gnu/bin:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/android-ndk/bin:/Users/arthur/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/bin"
VSLANG="1033"
"/android-ndk/bin/x86_64-linux-android33-clang"
"-m64"
"/tmp/rustcEr0LI7/symbols.o"
"/target/x86_64-linux-android/debug/deps/oratio_espeak-74e896619faec8e7.119cce293ejvq2cd.rcgu.o"
[other similar .rcgu.o omitted for brevity]
"/target/x86_64-linux-android/debug/deps/oratio_espeak-74e896619faec8e7.2s376qmbbifeevz2.rcgu.o"
"-Wl,--as-needed"
"-L"
"/target/x86_64-linux-android/debug/deps"
"-L"
"/target/debug/deps"
"-L"
"/target/x86_64-linux-android/debug/build/oratio-espeak-7547cefa827890c5/out/espeak-ng/x86_64-linux-android" # 该目录包含libespeak-ng.a
"-L"
"/Users/arthur/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-linux-android/lib"
"-lespeak-ng"
"-Wl,-Bstatic"
"/target/x86_64-linux-android/debug/deps/libespeakng_sys-70bc6650c0b39573.rlib"
"/Users/arthur/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-linux-android/lib/libtest-e3fab4d163e91148.rlib"
[other similar .rlib omitted for brevity]
"/Users/arthur/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-linux-android/lib/librustc_std_workspace_std-74e842bbf3699e1d.rlib"
"/target/x86_64-linux-android/debug/deps/libparking_lot-27cc7ea2042fb770.rlib"
[other similar .rlib omitted for brevity]
"/target/x86_64-linux-android/debug/deps/libeither-c29c058d37529903.rlib"
"/Users/arthur/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-linux-android/lib/libstd-37d05f9f3fc29d7b.rlib"
[other similar .rlib omitted for brevity]
"/Users/arthur/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-linux-android/lib/libcompiler_builtins-3a801941068d9a2c.rlib"
"-Wl,-Bdynamic"
"-lespeak-ng"
"-ldl"
"-llog"
"-lunwind"
"-ldl"
"-lm"
"-lc"
"-Wl,--eh-frame-hdr"
"-Wl,-z,noexecstack"
"-L"
"/Users/arthur/.rustup/toolchains/nightly-x86_64-unknown-linux-gnu/lib/rustlib/x86_64-linux-android/lib"
"-o"
"/target/x86_64-linux-android/debug/deps/oratio_espeak-74e896619faec8e7"
"-Wl,--gc-sections"
"-pie"
"-Wl,-z,relro,-z,now"
"-nodefaultlibs"

疑问 #

在库已被找到且确实包含目标符号的情况下，哪些原因会导致符号缺失？

内容的提问来源于stack exchange，提问作者Arthur Chaloin