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我在做一个动态库测试中老是不成功:
==== lib_test.cpp========
代码:
#include <iostream.h>;
#include <stdio.h>;
int prt( char * s )
{
cout << " this is in libtest.so !!! " << endl;
cout << s << endl;
return 0;
}
==================
cxx -fpic -c lib_test.cpp
cxx -shared -o libtest.so lib_test.o
生成动态库:libtest.so
其中: 系统提示,fpic 被忽略
==== test.cpp ==========
代码:
#include <iostream.h>;
#include <stdio.h>;
#include <dlfcn.h>;
//int upTo( char * );
int main( int argc , char *argv[] )
{
void * handle ; // the handle of the lib.so
char * erro_info = NULL;
int (*prt)( char* );// the function pointer
char str[80] = "";
cout << " ++++ enter in main ... ++++ " << endl;
cout << " ***.input a string " << endl;
cin >;>; str;
// open the *.so(*.dll) file
if ( ( handle = dlopen( "libtest.so" , RTLD_LAZY ) ) == NULL )
{
cout << " ***.error in open libtest.so " << endl;
return 0;
}
// get the function in libtest.so
if ( ( prt = ( int (*)(char*) )dlsym( handle , "prt" ) )== NULL )
{
cout << " ***.error in get function " << endl;
erro_info = dlerror( );
cout << " ***.the error information : " << erro_info << endl;
return 0;
}
// call the function in libtest.so
prt( str );
cout << str << endl;
// close the libtest.so
dlclose( handle );
return 1;
}
================================
编译连接主程序:
cxx test.cpp -o test -I/usr/include -I/usr/myapp -L/usr/ccs/lib -L/usr/myapp -lm -lcurses -ldl
现在问题有两个:
1。如果加上 -ldl 系统会连接不过,报错:
ld (prelink):
Can't locate file for: -ldl
ld:
Can't locate file for: -ldl
*** Exit 1
2。如果去掉 -ldl 连接通过,生成可执行文件 test 但是运行时不能调用动态库中的函数prt( char * s) 出错的地方是在:
代码:
// get the function in libtest.so
if ( ( prt = ( int (*)(char*) )dlsym( handle , "prt" ) )== NULL )
{
cout << " ***.error in get function " << endl;
erro_info = dlerror( );
cout << " ***.the error information : " << erro_info << endl;
return 0;
}
错误信息:
***.error in get function
***.the error information : dlsym: Unable to locate symbol prt
请高人指点,向同志们学习!!! |
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