为什么这个C函数在fclose崩溃了？

Question

请帮助我理解为什么这个函数在到达fclose时抛出异常:

void receive_file(int socket, char *save_to, int file_size) {
    FILE *handle = fopen(save_to,"wb");
    if(handle != NULL) {
        int SIZE = 1024;
        char buffer[SIZE];
        memset(buffer,0,SIZE);
        int read_so_far = 0;
        int read_now = 0;
        int reading_unit = (file_size < SIZE) ? file_size : SIZE;
        do {
            read_now = read(socket,buffer,reading_unit);
            fwrite(buffer,read_now,1,handle);
            read_so_far += read_now;
            if(read_so_far >= file_size) {
                break;
            }
            memset(buffer, 0, sizeof(buffer));
        } while (1);
        read_now = 0;
        fclose(handle);
    }
    else {
        extern int errno;
        printf("error creating file");
        printf(" error code : %d",errno);
        exit(-1);
    }
}

Eclipse CDT存在以下错误:

Single stepping until exit from function __kernel_vsyscall, 
which has no line number information.

此函数的目的是通过套接字接收文件.

编辑:我正在使用CentOS 5.3.问题是,文件是创建和编写的.即使MD5也是正确的.我不明白为什么它在fclose失败了.

EDIT2:这是我设法获得的堆栈跟踪:

*** glibc detected *** /home/linuser/workspace/proj/Debug/proj: free(): invalid next size (normal): 0x096a0068 ***
======= Backtrace: =========
/lib/libc.so.6[0x4fb0f1]
/lib/libc.so.6(cfree+0x90)[0x4febc0]
/lib/libc.so.6(fclose+0x136)[0x4e9c56]
/home/linuser/workspace/proj/Debug/proj[0x8048cd8]
/home/linuser/workspace/proj/Debug/proj[0x80492d6]
/home/linuser/workspace/proj/Debug/proj[0x804963d]
/lib/libc.so.6(__libc_start_main+0xdc)[0x4a7e8c]
/home/linuser/workspace/proj/Debug/proj[0x8048901]
======= Memory map: ========
001ff000-00200000 r-xp 001ff000 00:00 0          [vdso]
0046f000-00489000 r-xp 00000000 08:06 1280361    /lib/ld-2.5.so
00489000-0048a000 r-xp 00019000 08:06 1280361    /lib/ld-2.5.so
0048a000-0048b000 rwxp 0001a000 08:06 1280361    /lib/ld-2.5.so
00492000-005d0000 r-xp 00000000 08:06 1280362    /lib/libc-2.5.so
005d0000-005d2000 r-xp 0013e000 08:06 1280362    /lib/libc-2.5.so
005d2000-005d3000 rwxp 00140000 08:06 1280362    /lib/libc-2.5.so
005d3000-005d6000 rwxp 005d3000 00:00 0 
005d8000-005fd000 r-xp 00000000 08:06 1280369    /lib/libm-2.5.so
005fd000-005fe000 r-xp 00024000 08:06 1280369    /lib/libm-2.5.so
005fe000-005ff000 rwxp 00025000 08:06 1280369    /lib/libm-2.5.so
009b2000-009bd000 r-xp 00000000 08:06 1280372    /lib/libgcc_s-4.1.2-20080825.so.1
009bd000-009be000 rwxp 0000a000 08:06 1280372    /lib/libgcc_s-4.1.2-20080825.so.1
009c5000-00aa5000 r-xp 00000000 08:06 5465873    /usr/lib/libstdc++.so.6.0.8
00aa5000-00aa9000 r-xp 000df000 08:06 5465873    /usr/lib/libstdc++.so.6.0.8
00aa9000-00aaa000 rwxp 000e3000 08:06 5465873    /usr/lib/libstdc++.so.6.0.8
00aaa000-00ab0000 rwxp 00aaa000 00:00 0 
08048000-0804a000 r-xp 00000000 08:06 4884214    /home/linuser/workspace/proj/Debug/proj
0804a000-0804b000 rw-p 00001000 08:06 4884214    /home/linuser/workspace/proj/Debug/proj
096a0000-096c1000 rw-p 096a0000 00:00 0          [heap]
b7e00000-b7e21000 rw-p b7e00000 00:00 0 
b7e21000-b7f00000 ---p b7e21000 00:00 0 
b7f99000-b7f9a000 rw-p b7f99000 00:00 0 
b7faa000-b7fac000 rw-p b7faa000 00:00 0 
bfa82000-bfa97000 rw-p bffea000 00:00 0          [stack]

这是功能的"更新"版本:

void rec_file(int socket,char *path,int size)
{
    FILE *handle = fopen(path,"wb");
    char buffer[4096];
    int total_read = 0;
    if(handle != NULL)
    {
        while(1)
        {
            int bytes_read = recv(socket,buffer,4096,0);
            total_read    += bytes_read;
            if(bytes_read != -1)
            {
                fwrite(buffer,bytes_read,1,handle);
            }
            else
            {
                printf("read error ");
                exit(-1);
            }
            if(total_read >= size)
            {
                break;
            }
        }
        fclose(handle);
    }
    else
    {
        printf("error receiving file");
        exit(-1);
    }
}

也许这更干净？但是,我仍然收到相同的fclose异常.

EDIT3:我注释掉了所有内容,我只留下了下面的代码,遗憾的是,它仍然在fclose引发了异常:

void nrec(int sock,char* path,int size)
{
    FILE *handle = fopen(path,"wb");
    if(handle == NULL)
    {
        printf ("error opening file");
        return;
    }
    fclose(handle);
}

Answer 1

• fclose()返回一个值:如果文件成功关闭则返回0,否则返回EOF.考虑将代码修改为......

  if(fclose(handle)){printf("error closing file."); 出口(-1); }

• 正如其他人指出的那样,检查read()是否有错误.

• 如果在fclose返回0(成功)之后发生崩溃,并且所有read()都成功,则可能麻烦在其他地方.也许这是VLA.考虑将缓冲区代码更改为静态文件或malloc/free文件.

• 如果调用者误认为文件大小,并且声称该文件是500字节,而实际上它只有480,那么您的代码是否会永远读取套接字？