c - 记录 c 有时会给出 segafult

Question

正在我的应用程序中创建日志文件。应用程序将数据写入日志文件，并在大小达到 10 MB 时进行轮换(旧的删除，新的添加)。

This works fine ,but sometime it gives segafult.
The code for the same 

/* when the application starts the new file got created on the path*/
    char path[1024];
    char logpath[1024];
    char logfile_name[20] = "test";
    getcwd(path,1024);
    sprintf(logpath,"%s/TEST_LOGS/%s_%d_%d.log",path,logfile_name,
        app_inst_id,getpid());
     /
    logfptr = fopen(logpath,"a");
    if(logfptr == NULL)
    {
        printf("log file open failed\n");
        exit(0);
    }

最初创建的日志文件

int vlr_write_log(const char *format, va_list A)
{     
     struct stat st;
     char path[1024];
     char logpath[1024];
     char logfile_name[20] = "test";
     getcwd(path,1024);
     sprintf(logpath,"%s/TEST_LOGS/%s_%d_%d.log",path,logfile_name,
         app_inst_id,getpid());
     int size_in_byte = 10*1024*1024;
     if (logfptr!=NULL)
     {
         if( stat(logpath,&st) == 0)
         {
         /******* if file size is less than 10MB
                  append it to the log file also 
                  open it in write mode  *******/

             if( st.st_size < size_in_byte)
             {
                 vfprintf(logfptr,format,A);
             }
             else
             {
                 fflush(logfptr);
                 if(logfptr!= NULL)
                     fclose(logfptr);   // this gives the error 
                 logfptr = NULL;
                 logfptr = fopen(logpath,"w");
                 vfprintf(logfptr,format,A);
             }
         }
         else
         {
             if(logfptr!= NULL)
                 fclose(logfptr);
             logfptr = NULL;
             logfptr = fopen(logpath,"w");
             vfprintf(logfptr, format, A);
             fflush(logfptr);
         }
     }

     return 0;
}

以及相同的回溯

#0  0xffffe410 in __kernel_vsyscall ()
   #1  0x0036fe30 in raise () from /lib/libc.so.6
   #2  0x00371741 in abort () from /lib/libc.so.6
   #3  0x003a88cb in __libc_message () from /lib/libc.so.6
   #4  0x003b0c65 in _int_free () from /lib/libc.so.6
   #5  0x003b4c59 in free () from /lib/libc.so.6
   #6  0x0039f2d6 in fclose@@GLIBC_2.1 () from /lib/libc.so.6
   #7  0x08049aa7 in vlr_write_log (format=0xff99525c "[2014-01-10 17:06:13.416] key =       input_list:LM1561171389353710\n", A=0xff995374 "\340\\\231\377 \004"

)

谢谢萨罗杰

Answer 1

从堆栈跟踪中，您显然已经覆盖了堆上的某些内容。具体内容和位置尚不清楚，但它不会立即出现在您的日志记录代码中，因为它不会访问堆。 (尽管考虑到你一刀切的缩进，这是相当困难的)。

顺便说一句，这个:

char path[1024];
char logpath[1024];
getcwd(path,1024);
sprintf(logpath,"%s/TEST_LOGS/%s_%d_%d.log",path,logfile_name,app_inst_id,getpid());

可以更安全地编码为:

char path[1024];
char logpath[1024];
getcwd(path, sizeof(path));
snprintf(logpath, sizeof(logpath), "%s/TEST_LOGS/%s_%d_%d.log", path, logfile_name, app_inst_id, getpid());

如果你的路径有点大，你真的应该测试 getcwd 和 snprintf 的返回码