1 dynamiclibapp.c
2 Makefile
3 comm/inc/apue.h
4 comm/errorhandle.c
5 dynamiclib/Makefile
6 dynamiclib/dynamiclib_add.c
7 dynamiclib/dynamiclib_mul.c
8 dynamiclib/inc/dynamiclibs.h
9 dynamiclib/libs/

1 #ifndef __dynamic_libs_h__
2 #define __dynamic_libs_h__
3
4 #include "apue.h"
5 int dynamic_lib_func_add(int i1, int i2);
6 int dynamic_lib_func_mul(int i1, int i2);
7
8 #endif

1 #include "dynamiclibs.h"
2
3 int dynamic_lib_func_add(int i1, int i2)
4 {
5     int iret = i1 + i2;
6     printf("... in .so func, %d add %d,return %d\n", i1, i2, iret);
7     return iret;
8 }

1 #include "dynamiclibs.h"
2
3 int dynamic_lib_func_mul(int i1, int i2)
4 {
5     int iret = i1 * i2;
6     printf("... in .so func, %d multiplys %d, retun %d\n", i1, i2, iret);
7     return iret;
8 }

 1 CC       = gcc
 2 CFLAGS   = -Wall -g -O -fPIC     需要加上 -fPIC
 3 CXXFLAGS =
 4 INCLUDE  = -I ./inc -I ../comm/inc
 5 TARGET   = libmytest.so
 6 LIBPATH  = ./libs/
 7
 8 vpath %.h ./inc
 9
10 OBJS     = dynamiclib_add.o dynamiclib_mul.o
11 SRCS     = dynamiclib_add.c dynamiclib_mul.c
12
13 $(OBJS):$(SRCS)
14    $(CC) $(CFLAGS) $(INCLUDE) -c $^
15
16 all:$(OBJS)
17    $(CC) -shared -fPIC -o $(TARGET) $(OBJS)    需要加上 -shared -fPIC
18    mv $(TARGET) $(LIBPATH)
19
20 clean:
21    rm -f *.o
22    rm -f $(LIBPATH)*

 1 #include "apue.h"
 2 #include "dynamiclibs.h"
 3
 4 int main(int argc, char *argv[])
 5 {
 6     err_msg("step in main\n");
 7     dynamic_lib_func_add(1, 9);
 8     dynamic_lib_func_mul(1, 9);
 9     err_msg("step out main\n");
10
11     return 0;
12 }

 1 CC       = gcc
 2 CFLAGS   = -Wall -O -g
 3 CXXFLAGS =
 4 INCLUDE  = -I ./comm/inc -I ./dynamiclib/inc
 5 TARGET   = dynamiclibapp
 6 LIBVAR   = -lmytest             指明需要链接动态库 libmytest.so
 7 LIBPATH  = -L./dynamiclib/libs  指明 libmytest.so 的路径
 8 #search paths for errorhandler.c
 9 vpath %.c ./comm
10 #下行是为依赖项 apue.h 准备的，比如 [errorhandler.o:errorhandler.c apue.h] 里的 apue.h
11 vpath %.h ./comm/inc
12
13 OBJS     = errorhandler.o dynamiclibapp.o
14 #下行的 apue.h，可以不必写出来
15 errorhandler.o:errorhandler.c apue.h
16    $(CC) $(CFLAGS) $(INCLUDE) -c $^
17 dynamiclibapp.o:dynamiclibapp.c apue.h
18    $(CC) $(CFLAGS) $(INCLUDE) -c $^
19
20 all:$(OBJS) $(LIB)
21    cd ./dynamiclib && make all
22    $(CC) $(CFLAGS) $(INCLUDE) -o $(TARGET) $(OBJS) $(LIBPATH) $(LIBVAR)
23    在上行中，在执行编译时，加载了 libmytest.so 中函数
24 clean:
25    rm -f *.o
26    rm -f comm/inc/*.gch
27    rm -f $(TARGET)
28    cd ./dynamiclib && make clean

1 /home/lijiangtao/dynamiclib/libs

 1 #include "apue.h"
 2 #include "dynamiclibs.h"
 3 #include <dlfcn.h>
 4
 5 typedef int (*fp_lib_add)(int, int);
 6 typedef int (*fp_lib_mul)(int, int);
 7 typedef void* dlhandle;
 8
 9 dlhandle      dll      = NULL;
10 fp_lib_add    func_add = NULL;
11 fp_lib_mul    func_mul = NULL;
12
13 dlhandle load_dynamic_func(char *psopath, fp_lib_add *padd, fp_lib_mul *pmul);
14
15 int main(int argc, char *argv[])
16 {
17     char *pso = "/home/lijiangtao/dynamiclib/libs/libmytest.so";//指定 .so 路径
18     dll = load_dynamic_func(pso, &func_add, &func_mul);//程序执行时，加载动态函数
19     err_msg("step in main\n");
20     func_add(1, 9);//执行 add 函数
21     func_mul(1, 9);//执行 mul 函数
22     err_msg("step out main\n");
23
24     return 0;
25 }
26
27 dlhandle load_dynamic_func(char *psopath, fp_lib_add *padd, fp_lib_mul *pmul)
28 {
29     if(NULL == psopath ||'\0' == psopath[0])
30         return NULL;
31     char *perrormsg = NULL;
32     dlhandle dllhandle = dlopen(psopath, RTLD_LAZY);
33     if(NULL == dllhandle)
34     {
35         printf("%s\n", dlerror());
36         return NULL;
37     }
38     if(NULL != padd)
39     {
40         *padd = dlsym(dllhandle, "dynamic_lib_func_add");//加载 add 函数
41         perrormsg = dlerror();
42         if(NULL != perrormsg)
43             printf("%s\n", perrormsg);
44     }
45     if(NULL != pmul)
46     {
47         *pmul = dlsym(dllhandle, "dynamic_lib_func_mul");//加载 mul 函数
48         perrormsg = dlerror();
49         if(NULL != perrormsg)
50             printf("%s\n", perrormsg);
51     }
52     return dllhandle;
53 }

 1 CC       = gcc
 2 CFLAGS   = -Wall -O -g
 3 CXXFLAGS =
 4 INCLUDE  = -I ./comm/inc -I ./dynamiclib/inc
 5 TARGET   = dynamiclibapp
 6 LIBVAR   = -ldl    需要链接 libdl.so 库
 7 LIBPATH  =
 8 #search paths for errorhandler.c
 9 vpath %.c ./comm
10 #下行是为依赖项 apue.h 准备的，比如 [errorhandler.o:errorhandler.c apue.h] 里的 apue.h
11 vpath %.h ./comm/inc
12
13 OBJS     = errorhandler.o dynamiclibapp.o
14 #下行的 apue.h，可以不必写出来
15 errorhandler.o:errorhandler.c apue.h
16    $(CC) $(CFLAGS) $(INCLUDE) -c $^
17 dynamiclibapp.o:dynamiclibapp.c apue.h
18    $(CC) $(CFLAGS) $(INCLUDE) -c $^
19
20 all:$(OBJS) $(LIB)
21    cd ./dynamiclib && make all
22    $(CC) $(CFLAGS) -rdynamic $(INCLUDE) -o $(TARGET) $(OBJS) $(LIBPATH) $(LIBVAR)
23    在上行，执行编译时并没有加载动态接口函数，而是在应用程序执行时加载的；需要 -rdynamic 选项，      以确保 dlopen 这些接口可用
24 clean:
25    rm -f *.o
26    rm -f $(TARGET)
27    cd ./dynamiclib && make clean