源文件（這是Rechard Steven在unix 高級編程的代碼）
# cat liberr.h
#ifndef _LIBERR_H
#define _LIBERR_H
#include <stdarg.h>
#define MAXLINELEN 4096
void err_ret(const char *fmt, ...);
void err_quit(const char *fmt, ...);
void log_ret (char *logfile,const char *fmt, ...);
void log_quit(char *logfile,const char *fmt, ...);
void err_prn(const char *fmt,va_list ap, char *logfile);
#endif
# cat liberr.c
#include <errno.h>
#include <stdarg.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include "liberr.h"
void err_ret(const char *fmt, ...)
{
va_list ap;
va_start(ap,fmt);
err_prn(fmt,ap,NULL);
va_end(ap);
return;
}
void err_quit(const char *fmt, ...)
{
va_list ap;
va_start(ap, fmt);
err_prn(fmt, ap, NULL);
va_end(ap);
exit(EXIT_FAILURE);
}
void log_ret(char *logfile,const char *fmt, ...)
{
va_list ap;
va_start(ap,fmt);
err_prn(fmt,ap,logfile);
va_end(ap);
return;
}
void log_quit(char * logfile,const char *fmt, ...)
{
va_list ap;
va_start(ap,fmt);
err_prn(fmt,ap,logfile);
va_end(ap);
exit(EXIT_FAILURE);
}
extern void err_prn(const char *fmt, va_list ap, char *logfile)
{
int save_err;
char buf[MAXLINELEN];
FILE *plf;
save_err=errno;
vsprintf(buf,fmt,ap);
sprintf(buf + strlen(buf),":%s",strerror(save_err));
strcat(buf,"\n");
fflush(stdout);
if(logfile != NULL)
if((plf = fopen(logfile,"a")) != NULL ) {
fputs(buf,plf);
fclose(plf);
} else
fputs("failed to open log file\n,", stderr);
else
fputs(buf,stderr);
fflush(NULL);
return;
}
編譯及打包靜態包
#gcc -c liberr.c -o liberr.o
#ar rcs liberr.a liberr.o
# cat errtest.c
#include <stdio.h>
#include <stdlib.h>
#include "liberr.h"
#define ERR_QUIT_SKIP 1
#define LOG_QUIT_SKIP 1
int main(void)
{
FILE *pf;
puts("Tesing err_ret");
if((pf = fopen("foo","r")) == NULL) {
err_ret("%s %s","err_ret:","failed to open foo");
}
puts("Tesing log_ret");
if((pf = open("foo","r")) == NULL) {
log_ret("errtest.log","%s %s","log_ret:","failed to open foo");
}
#ifndef ERR_QUIT_SKIP
puts("Testing err_quit");
if((pf = open("foo","r")) == NULL) {
err_ret("%s %s","err_ret:","failed to open foo");
}
#endif
#ifndef LOG_QUIT_SKIP
puts("Testing log_quit");
if((pf = open("foo","r")) == NULL) {
log_ret("errtest.log","%s %s","log_quit:","failed to open foo");
}
#endif
exit(EXIT_SUCCESS);
}
靜態庫編譯：
[root@pc201 linux_guide]# gcc errtest.c -o errtest -L. -lerr --static
errtest.c: In function ‘main’:
errtest.c:18: warning: assignment makes pointer from integer without a cast
/usr/bin/ld: cannot find -lc
collect2: ld returned 1 exit status
解決辦法是安裝glibc-static
[root@pc201 linux_guide]# yum install glibc-static
Loaded plugins: fastestmirror
Loading mirror speeds from cached hostfile
* base: mirrors.163.com
* extras: mirrors.163.com
* updates: ftp.stu.edu.tw
Setting up Install Process
Resolving Dependencies
--> Running transaction check
.... ..... ..........
Complete!
再次運行就沒有報錯了
[root@pc201 linux_guide]# gcc errtest.c -o errtest -L. -lerr --static
errtest.c: In function ‘main’:
errtest.c:18: warning: assignment makes pointer from integer without a cast
與動態庫分析：
建立動態庫：
#gcc -fPIC -g -c liberr.c -o liberr.o
#gcc -g -shared -Wl,soname,liberr.so -o liberr.so.1.0.0 liberr.o -lc
動態鏈接編譯的結果
靜態編譯的結果
看到比動態鏈接的大接近100倍。
下面示例調用動態庫內部的函數。這裡，我們要調用liberr.so裡的err_ret函數：
# cat dltest.c
#include <stdio.h>
#include <stdlib.h>
#include <dlfcn.h>
int main(void)
{
void *handle;
void (*errfcn) (const char *fmt, ...); //errfcn是函數指針，它要指向要調用的err_ret
const char *errmsg;
FILE *pf;
handle = dlopen("./liberr.so",RTLD_NOW); // dlopen打開liberr.so，返回handle
if(handle==NULL) {
fprintf(stderr,"Failed to load liberr.so:%s\n",dlerror());
exit(EXIT_FAILURE);
}
dlerror(); // reset dl error
errfcn=dlsym(handle,"err_ret"); // dlsym 尋找handle裡的err_ret函數
if((errmsg = dlerror()) != NULL) {
fprintf(stderr,"Didn't find err_ret:%s\n",errmsg);
exit(EXIT_FAILURE);
}
if((pf = fopen("foobar","r")) == NULL) {
errfcn("Couldn't open foobar");
}
dlclose(handle); //關閉handle
exit(EXIT_FAILURE);
}
編譯
gcc -g dltest.c -Wall -ldl -o dltest
執行結果
無結果，調試：
發現代碼少了一段
if((pf = fopen("foobar","r")) == NULL) {
errfcn("Couldn't open foobar");
}
加進去，編譯，執行
Unix環境高級編程 源代碼地址 http://www.linuxidc.com/Linux/2011-04/34826.htm
Unix環境高級編程源碼編譯 http://www.linuxidc.com/Linux/2011-09/42503.htm
apue.h頭文件（Unix環境高級編程） http://www.linuxidc.com/Linux/2012-01/51729.htm
《Unix環境高級編程》（第二版）apue.h的錯誤 http://www.linuxidc.com/Linux/2011-04/34662.htm
Unix環境高級編程第二版讀書筆記 http://www.linuxidc.com/Linux/2011-04/34235.htm
《Unix環境高級編程》中apue.h的問題 http://www.linuxidc.com/Linux/2013-01/77686.htm
Linux升級GCC 4.8.1清晰簡明教程(Ubuntu 12.04 64位版為例) http://www.linuxidc.com/Linux/2014-04/99583.htm
Ubuntu下Vim+GCC+GDB安裝及使用 http://www.linuxidc.com/Linux/2013-01/78159.htm
Ubuntu下兩個GCC版本切換 http://www.linuxidc.com/Linux/2012-10/72284.htm
CentOS6.5升級手動安裝GCC4.8.2 http://www.linuxidc.com/Linux/2015-01/112595.htm
GCC 的詳細介紹：請點這裡
