Linux静态库与动态库的创建与使用

1、目录树
|-- app
| |-- Makefile
| `-- test.c
|-- Makefile
`-- mylib
|-- Makefile
|-- myadd.c
|-- myadd.h
|-- mysub.c
`-- mysub.h

2、静态库的创建
（1）app/Makefile
OBJS=test.o
INCLUDE_DIR=../mylib
CFLAGS += -I$(INCLUDE_DIR)
LDFLAGS += -L$(INCLUDE_DIR)

test : $(OBJS)
    $(CC) $(CFLAGS) $(LDFLAGS) $^ -o $@ -lmy

.PHONY : clean
clean:
    -rm *.o test

（2）app/test.c
#include <stdio.h>
#include "myadd.h"
#include "mysub.h"

int main()
{
    int a=5,b=3;
    printf("%d+%d=%d %d-%d=%d/n", a, b, myadd(a, b), a, b, mysub(a, b));
    return 0;
}

（3）Makefile
CC = gcc
LD = ld
AR = ar
ARFLAGS = -cr
export CC LD AR ARFLAGS

SUBDIRS = mylib app

.PHONY : all
all:
    @for subdir in $(SUBDIRS); /
    do /
        ( cd $subdir && $(MAKE)) || exit 1; /
    done

.PHONY : clean
clean:
    @ for subdir in $(SUBDIRS); /
    do /
        (make clean -C $subdir); /
    done

（4）mylib/Makefile
OBJS = myadd.o mysub.o

libmy.a : $(OBJS)
    $(AR) $(ARFLAGS) $@ $^

%.o: %.c %.h
    $(CC) -c tiny_mce_markerlt;

.PHONY : clean
clean:
    -rm *.o *.a
【说明】tiny_mce_markerlt;改为$^时，会生成xxx.h.gch文件。将.h文件当成.c文件一样来编译就会生成.gch文件，这是gcc的预编译头技术，可以提高编译速度

（5）mylib/myadd.c
#include "myadd.h"

int myadd(int a, int b)
{
    return a+b;
}

（6）mylib/myadd.h
#ifndef __MYADD_H__
#define __MYADD_H__

int myadd(int a, int b);

#endif

（7）mylib/mysub.c
#include "mysub.h"

int mysub(int a, int b)
{
    return a-b;
}

（8）mylib/mysub.h
#ifndef __MYSUB_H__
#define __MYSUB_H__

int mysub(int a, int b);

#endif

3、动态库的创建
mylib/Makefile
OBJS = myadd.o mysub.o

libmy.so : $(OBJS)
    gcc -shared -fPCI $^ -o $@

%.o: %.c %.h
    $(CC) -c tiny_mce_markerlt;

.PHONY : clean
clean:
    -rm *.o *.so

4、动态库的使用
$ ldd ./app/test
    linux-gate.so.1 => (0x0085c000)
    libmy.so => not found
    libc.so.6 => /lib/libc.so.6 (0x00221000)
    /lib/ld-linux.so.2 (0x00200000)

$ ./app/test
    ./app/test: error while loading shared libraries: libmy.so: cannot open shared object file: No such file or directory

$export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:./mylib

$ ldd ./app/test
    linux-gate.so.1 => (0x00b29000)
    libmy.so => ./mylib/libmy.so (0x00246000)
    libc.so.6 => /lib/libc.so.6 (0x00248000)
    /lib/ld-linux.so.2 (0x00200000)

$ ./app/test
    5+3=8 5-3=2