Linux动态链接库的使用

file

ldd

nm

readelf -a smu.o

objdump -d sum.o

#include <stdio.h>
#include <stdlib.h>

int sum(int x){
 int i, result=0;
 for(i=0; i<=x; i++){
  result+=i;
  }
 if(x > 100)
  exit(-1);
 return result;
};

void display(char* msg){
 printf("%s\n",msg);
}
 
int add(float a,float b){
 return a+b;
}

int sum_array(int array[], int num){
 int i =0, sum = 0; 
 for(i=0; i<num; ++i) 
  sum += array[i];
 return sum;
}

void modify_array(int array[], int num){
 int i =0, sum = 0; 
 for(i=0; i<num; ++i) 
  array[i] *= 10;
}

#include <stdio.h>
#include <stdlib.h>

int main(void){
 int x;
 printf("Input an integer:\n");
 scanf("%d", &x);
 printf("sum=%d\n", sum(x));
 return 0;
};

gcc -c main.c -o main.o
gcc -c sum.c -o sum.o
gcc sum.o main.o

file main  // ELF 64-bit LSB executable
file sum.o // ELF 64-bit LSB relocatable

gcc sum.o -shared -o sum.so

gcc -c sum.c -fPIC -o sum.o
gcc sum.o -o shared sum.so

gcc -shared -fPIC -o libmyhello.so hello.o
gcc -o hello main.c -L. -lmyhello

ar rcs libxx.a xx.o 
g++ -o main main.cpp -static -L. -lxx

g++ -o main main.c sum.so
./main 

ldd main
output:
sum.so => not found

export $LD_LIBRARY_PATH=pwd:$LD_LIBRARY_PATH