动态C / C ++为Android 2.2 lib目录下:错误符号未找到 [英] Dynamic C/C++ lib for Android 2.2: error Symbol not found
问题描述
我有两个项目。其中之一是Android应用程序与本地code,刚刚加载动态库android_lib.so。
另一个项目是,库(android_lib.so)。这个库的code是简单的只是学习的事情是怎么回事。它只有一个功能。这里是:
INT计算(INT X,int y)对
{
回报(X * X + Y * Y);
}
在的Makefile 我用的跨平台,Android 2.2的工具链compilator (/usr/local/android-ndk-r8/toolchains/arm-linux-androideabi4.4.3/$p$pbuilt/linux-x86/bin/arm-linux-androideabi-gcc):
<$p$p><$c$c>NDK_DIR=/usr/local/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/$p$pbuilt/linux-x86/binANDROID_GCC = $(NDK_DIR)/ ARM-Linux的androideabi-GCC
NDK_ROOT =的/ usr /本地/ Android的NDK-R8CPPFLAGS = $(NDK_ROOT)/平台/ Android的-8 /弓臂/ usr / include目录
CFLAGS = -nostdlib
LDFLAGS = -Wl,-rpath链接= $(NDK_ROOT)/平台/ Android的-8 /弓臂/ usr / lib目录/ -L $(NDK_ROOT)/平台/ Android的-8 /弓臂/ usr / lib目录/
LIBS = -lcandroid_lib.so:calculate.o
$(ANDROID_GCC)$(CFLAGS)-o -shared android_lib.so calculate.ocalculate.o:calculate.c
$(ANDROID_GCC)$(CPPFLAGS)$(CFLAGS)-c -fPIC calculate.c
清洁:
RM -f * *的.o。所以
于是我输入make并获得 android_lib.so 。
在Android项目的一部分原生(它是混合的Java / C ++的Eclipse项目),我调用dlopen的()
dl_handle =的dlopen(LIB,RTLD_LAZY);
如果(!dl_handle){
误差=(字符*)dlerror获得();
如果(错误!= NULL){
__android_log_print(ANDROID_LOG_INFO,本土code,错误);
返回-1;
}
其他{
sprintf的(sError%s没有找到,LIB);
__android_log_print(ANDROID_LOG_INFO,本土code,sError);
返回-2;
}
}
它成功地加载android_lib.so。但是,如果我试图调用函数计算()我得到错误。
FUNC =(INT(*)(INT,INT))的dlsym(dl_handle,计算);
误差=(字符*)dlerror获得();
如果(错误!= NULL){
__android_log_print(ANDROID_LOG_INFO,本土code,错误);
返回-3;
}
函数返回-3在Eclipse的LogCat中,我可以看到
7月1日至1日:00:44.624:I /本地code(8696):找不到符号:
请帮我解决这个问题。
更新
$ CD /usr/local/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/$p$pbuilt/linux-x86/bin
$ sudo的./arm-linux-androideabi-objdump -T /home/chet/workspace/dinLib/android_lib.so/home/chet/workspace/dinLib/android_lib.so:文件格式ELF32-littlearm动态符号表:
00000234升ð的.text 00000000的.text
00000274克D * ABS * 00000000 __exidx_end
000012e0克D- * ABS * 00000000 _bss_end__
00000234克DF 00000040 .text区段计算
000012e0克D- * ABS * 00000000 __bss_start__
00000274克D * ABS * 00000000 __exidx_start
000012e0克D- * ABS * 00000000 __bss_end__
000012e0克D- * ABS * 00000000 __bss_start
000012e0克D- * ABS * 00000000 __END__
000012e0克D- * ABS * 00000000 _edata
000012e0克D- * ABS * 00000000 _end
000012e0克D- .GOT 00000000 __data_start
一些重要的规则:
- 您应该使用
NDK的构建
,而不是直接ARM-Linux的androideabi-GCC
- 在
Android.mk
:LOCAL_LDFLAGS + =轮候册, - 出口动态
- 如果
dlerror获得()
返回错误并不意味着则dlsym()
失败。检查则dlsym()
真的返回NULL
。因为它可能会返回一个有效的地址,但dlerror获得()
可能会返回错误找不到符号在同一时间%)),我有这个愚蠢的错误!见code。 - 您不需要调用
的System.loadLibrary(your_lib.so)
。只有的dlopen(your_lib.so)
从本地code与RTLD_NOW
或RTLD_LAZY
不管! -
确保
your_lib.so
位于/数据/数据/ APP_NAME /库
FUNC =(INT(*)(INT,INT))的dlsym(dl_handle,计算);
误差=(字符*)dlerror获得();
如果(!错误= NULL){//将其替换为IF((FUNC == NULL)及及(误差= NULL)!)
__android_log_print(ANDROID_LOG_INFO,本土code,错误);
返回-3;
}
库类型下一选项
这是所有:)
I have two projects. One of them is Android app with native code, which just loads dynamically library android_lib.so.
Another project is that library (android_lib.so). Code of this library is simple just for learning how things are going. It has only one function. Here is it:
int calculate (int x, int y)
{
return (x*x+y*y);
}
In Makefile I use cross-platform compilator from Android 2.2 toolchains (/usr/local/android-ndk-r8/toolchains/arm-linux-androideabi4.4.3/prebuilt/linux-x86/bin/arm-linux-androideabi-gcc):
NDK_DIR=/usr/local/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/bin
ANDROID_GCC=$(NDK_DIR)/arm-linux-androideabi-gcc
NDK_ROOT=/usr/local/android-ndk-r8
CPPFLAGS = $(NDK_ROOT)/platforms/android-8/arch-arm/usr/include
CFLAGS =-nostdlib
LDFLAGS = -Wl,-rpath-link=$(NDK_ROOT)/platforms/android-8/arch-arm/usr/lib/ -L$(NDK_ROOT)/platforms/android-8/arch-arm/usr/lib/
LIBS=-lc
android_lib.so: calculate.o
$(ANDROID_GCC) $(CFLAGS) -shared -o android_lib.so calculate.o
calculate.o: calculate.c
$(ANDROID_GCC) $(CPPFLAGS) $(CFLAGS) -c -fPIC calculate.c
clean:
rm -f *.o *.so
So I type make and get android_lib.so. In native part of android project (it is mixed Java/C++ Eclipse project) I call dlopen()
dl_handle = dlopen( lib, RTLD_LAZY );
if (!dl_handle) {
error = (char *) dlerror();
if (error != NULL) {
__android_log_print(ANDROID_LOG_INFO,"nativeCode",error);
return -1;
}
else {
sprintf(sError,"%s is not found",lib);
__android_log_print(ANDROID_LOG_INFO,"nativeCode",sError);
return -2;
}
}
It succesfully loads android_lib.so. But if I am trying to call function calculate() I get error.
func = (int (*)(int, int)) dlsym( dl_handle, "calculate" );
error = (char *) dlerror();
if (error != NULL) {
__android_log_print(ANDROID_LOG_INFO,"nativeCode",error);
return -3;
}
Function returns -3 and in LogCat of Eclipse I can see
01-01 07:00:44.624: I/nativeCode(8696): Symbol not found:
Please help me to solve this issue.
Update:
$ cd /usr/local/android-ndk-r8/toolchains/arm-linux-androideabi-4.4.3/prebuilt/linux-x86/bin
$ sudo ./arm-linux-androideabi-objdump -T /home/chet/workspace/dinLib/android_lib.so
/home/chet/workspace/dinLib/android_lib.so: file format elf32-littlearm
DYNAMIC SYMBOL TABLE:
00000234 l d .text 00000000 .text
00000274 g D *ABS* 00000000 __exidx_end
000012e0 g D *ABS* 00000000 _bss_end__
00000234 g DF .text 00000040 calculate
000012e0 g D *ABS* 00000000 __bss_start__
00000274 g D *ABS* 00000000 __exidx_start
000012e0 g D *ABS* 00000000 __bss_end__
000012e0 g D *ABS* 00000000 __bss_start
000012e0 g D *ABS* 00000000 __end__
000012e0 g D *ABS* 00000000 _edata
000012e0 g D *ABS* 00000000 _end
000012e0 g D .got 00000000 __data_start
Some important rules:
- you should use
ndk-build
instead directlyarm-linux-androideabi-gcc
- in
Android.mk
of library type next options:LOCAL_LDFLAGS += -Wl,--export-dynamic
- if
dlerror()
returns error it doesn't mean thatdlsym()
failed. Check ifdlsym()
really returnsNULL
. Because it may return a valid address butdlerror()
may return error "Symbol not found" at the same time %)) I had this stupid mistake!!! See code. - You do not need call
System.LoadLibrary(your_lib.so)
. Onlydlopen("your_lib.so")
from native code withRTLD_NOW
orRTLD_LAZY
no matter! Be sure that
your_lib.so
is situated in/data/data/app_name/libs
func = (int (*)(int, int)) dlsym( dl_handle, "calculate" ); error = (char *) dlerror(); if (error != NULL) { //replace it with if ((func == NULL)&& (error != NULL)) __android_log_print(ANDROID_LOG_INFO,"nativeCode",error); return -3; }
That's all :)
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