Unix/Linux C动态库的使用
动态库的生成：
gcc -O -fpic -shared -o share.so share.c
有的gcc版本可以用"-G"替换"-shared"选项.
eg.使用动态库
#cc -O test.c ./share.so
eg.带路径编译
#cc -O test.c ./lib/share.so
当执行./a.out时，操作系统会自动在当前目录lib下查找share.so，若找不到程序将被杀.
当然也可以通过更改环境变量:
#LD_LIBRARY_PATH=./:share
#export LD_LIBRARY_PATH
#./a.out
例程：
dll1.c
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#include <stdio.h>
int p = 1;
void print()
{
printf("This is the first dll lib provided function: print().\n");
return;
}
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dll2.c
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#include <stdio.h>
int p = 2;
void print()
{
printf("This is the second dll lib provided function: print().\n");
return;
}
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implicit_test.c
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int main (int argc, char *argv[])
{
print();
return 0;
}
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explicit_test.c
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#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
int main(int argc, char *argv[])
{
void *handle; /* pointer of dll lib handle */
void (*pfunc)();
int *p;
handle = dlopen("./dll1.so", RTLD_NOW); /* RTLD_LAZY mode, parsed symbol
when called */
p = (int *)dlsym(handle, "p");
if (p != NULL)
{
printf("p = %d.\n", *p);
}
if ( dlsym(handle, "pp") == NULL ) /* none exist variable pp */
{
printf( "%s\n", dlerror() ); /* print error, and clean */
}
pfunc = (void (*)())dlsym(handle, "print");
if (pfunc != NULL)
{
pfunc();
}
dlclose(handle);
return 0;
}
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Makefile
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LIB= -ldl
dll:
gcc -O -fpic -shared -o dll1.so dll1.c
gcc -O -fpic -shared -o dll2.so dll2.c
# some version of gcc supports "-G" instead of "-shared" option
implicit_test:
gcc -O -o implicit_test implicit_test.c ./dll1.so
# argument: ./dll1.so, explicitly tell the os to search dll location.
# if not told path, when running, os will implicitly search at default
# +LD_LIBRARY_PATH=./:dll/
explicit_test:
gcc -O -o explicit_test $(LIB) explicit_test.c
clean:
rm -f dll1.so dll2.so implicit_test explicit_test
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