使用动态库交叉编译 C 代码时出错 [英] Error during Cross-compiling C code with Dynamic libraries
问题描述
我有两个文件:
lib.c
#include<stdio.h>
void hi() {
printf("Hi i'm a library function in lib.so\n");
}
和 main.c
#include<stdio.h>
#include<dlfcn.h>
/* based on Jeff Scudder's code */
int main() {
void *SharedObjectFile;
void (*hi)();
// Load the shared libary;
SharedObjectFile = dlopen("./lib.so", RTLD_LAZY);
// Obtain the address of a function in the shared library.
ciao = dlsym(SharedObjectFile, "hi");
// Use the dynamically loaded function.
(*hi)();
dlclose(SharedObjectFile);
}
我尝试使用以下命令构建可执行文件:
And I've tried to build an executables using the following commands:
导出 LD_LIBRARY_PATH=pwd
export LD_LIBRARY_PATH=
pwd
gcc -c -fpic lib.c
gcc -c -fpic lib.c
gcc -shared -lc -o lib.so lib.o
gcc -shared -lc -o lib.so lib.o
gcc main.c -ldl
gcc main.c -ldl
而且效果很好.然后我尝试使用以下命令在 Android(Nexus One，带有 ARM-v7-0a arch)上导出我的程序:
And it works pretty well. Then I've tried to export my program on Android (Nexus One, with ARM-v7-0a arch) using the following commands:
导出 LD_LIBRARY_PATH=pwd
export LD_LIBRARY_PATH=
pwd
arm-none-linux-gnueabi-gcc -c -fpic lib.c
arm-none-linux-gnueabi-gcc -c -fpic lib.c
arm-none-linux-gnueabi-gcc -shared -lc -o lib.so lib.o
arm-none-linux-gnueabi-gcc -shared -lc -o lib.so lib.o
arm-none-linux-gnueabi-gcc main.c -ldl -o main
arm-none-linux-gnueabi-gcc main.c -ldl -o main
adb push main/system/app
adb push main /system/app
在我的智能手机上的正确文件夹上执行 ./main 的结果是:
The result of executing ./main on the correct folder on my smartphone is just:
./main: 未找到
./main: not found
即使我的文件就在那里！
even if my file is right there!
我在交叉编译过程中遗漏了什么吗?有什么帮助吗?我正在使用 CodeSourcery 的交叉编译器，它适用于没有 .so 库的静态程序.谢谢
Am I missing anything during the cross-compile process? Any help? I'm using the cross-compiler from CodeSourcery and it works well for static programs without .so libraries. Thanks
EDIT:正如 Igor 在下面所说的，这是一个链接器问题.此命令修复它:
EDIT: as Igor states below, that was a linker issue. This command fixes it:
arm-none-linux-gnueabi-gcc -o test main.c -Wl,--dynamic-linker=/system/bin/linker -ldl
arm-none-linux-gnueabi-gcc -o test main.c -Wl,--dynamic-linker=/system/bin/linker -ldl
就我而言，我需要其他库，因为在/system/lib/中没有很多 .so 文件.
in my very case I need other libraries because in /system/lib/ there are no many .so files.
推荐答案
未找到"消息不是指共享对象，而是指动态链接器.Linux 使用 /lib/ld-linux.so.2(或 /lib64/ld-linux-x86-64.so.2 for x64)而 Android 使用 /bin/链接器.您可以使用 readelf -l 检查您的程序使用的动态加载器，例如:
The "not found" message refers not to the shared object but to the dynamic linker. Linux uses /lib/ld-linux.so.2 (or /lib64/ld-linux-x86-64.so.2 for x64) while Android uses /bin/linker. You can check which dynamic loader your program uses with readelf -l, e.g.:
Program Headers:
Type Offset VirtAddr PhysAddr FileSiz MemSiz Flg Align
PHDR 0x000034 0x08048034 0x08048034 0x00100 0x00100 R E 0x4
INTERP 0x000134 0x08048134 0x08048134 0x00013 0x00013 R 0x1
[Requesting program interpreter: /lib/ld-linux.so.2]
您可以指定与 ld 的 --dynamic-linker 开关一起使用的链接器，但可能存在其他差异.例如，Android 使用称为仿生的精简 libc 实现，它可能缺少您的程序所依赖的功能，或者具有不同的行为.
You can specify a linker to use with ld's --dynamic-linker switch, but there are likely to be other differences. For example, Android uses a stripped-down libc implementation called bionic, and it may be missing functionality that your program relies on, or have different behavior.
在为 Android 编译程序时，您应该使用 NDK 或其他面向 Android 的工具链.尽管它基于 Linux 内核，但差异足够大，以至于针对 Linux 的工具链是不够的.
You should use NDK or another Android-targeted toolchain when compiling programs for Android. Even though it's based on Linux kernel, the differences are large enough that Linux-targeted toolchains are not sufficient.
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