Andorid之jni里面崩溃然后用errno分析结果解决问题

1、问题

在jni里面程序崩溃了，初步定位是这行代码，下面的结果运行既然小于0，我觉得很奇怪，理论上不应该啊，想不到为什么会小于0

if ((sock_fd = socket(PF_INET, SOCK_STREAM, 0)) < 0) {

2、解决办法

在文件里面加上#include<errno.h>头文件，既然这里出错了，就用errno,然后在这个崩溃地方打印出这个 errno的值，

errno是记录系统的最后一次错误代码。代码是一个int型的值，在errno.h中定义。查看错误代码errno是调试程序的一个重要方法。当linux C api函数发生异常时,一般会将errno变量(需include errno.h)赋一个整数值,不同的值表示不同的含义,可以通过查看该值推测出错的原因.

加上下面的代码：

 LOGE("sock_fd is %d:%d\n", sock_fd, errno);

发现errno的值是13，然后马上查errno值是13的时候，是什么原因导致，

#define EACCES 13 /* Permission denied */

然后发现权限没有定义，难道访问sdcard也需要权限？，后面一想应该是AndroidManifest.xml权限不够，加上网络权限和sdcard读取权限

    <uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />    <uses-permission android:name="android.permission.INTERNET" />    <uses-permission android:name="android.permission.READ_PHONE_STATE" />    <uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

没有崩溃了，完美解决。

3、总结

在写linux c代码的时候，如果遇到崩溃，莫名其妙的错误，不好分析的时候，记得第一条件反射是打打印errno的值，切记，然后这里也给出errno数值对应相关的错误意义。

#define EPERM 1 /* Operation not permitted */　　#define ENOENT 2 /* No such file or directory */　　#define ESRCH 3 /* No such process */　　#define EINTR 4 /* Interrupted system call */　　#define EIO 5 /* I/O error */　　#define ENXIO 6 /* No such device or address */　　#define E2BIG 7 /* Argument list too long */　　#define ENOEXEC 8 /* Exec format error */　　#define EBADF 9 /* Bad file number */　　#define ECHILD 10 /* No child processes */　　#define EAGAIN 11 /* Try again */　　#define ENOMEM 12 /* Out of memory */　　#define EACCES 13 /* Permission denied */　　#define EFAULT 14 /* Bad address */　　#define ENOTBLK 15 /* Block device required */　　#define EBUSY 16 /* Device or resource busy */　　#define EEXIST 17 /* File exists */　　#define EXDEV 18 /* Cross-device link */　　#define ENODEV 19 /* No such device */　　#define ENOTDIR 20 /* Not a directory */　　#define EISDIR 21 /* Is a directory */　　#define EINVAL 22 /* Invalid argument */　　#define ENFILE 23 /* File table overflow */　　#define EMFILE 24 /* Too many open files */　　#define ENOTTY 25 /* Not a typewriter */　　#define ETXTBSY 26 /* Text file busy */　　#define EFBIG 27 /* File too large */　　#define ENOSPC 28 /* No space left on device */　　#define ESPIPE 29 /* Illegal seek */　　#define EROFS 30 /* Read-only file system */　　#define EMLINK 31 /* Too many links */　　#define EPIPE 32 /* Broken pipe */　　#define EDOM 33 /* Math argument out of domain of func */　　#define ERANGE 34 /* Math result not representable */　　#define EDEADLK 35 /* Resource deadlock would occur */　　#define ENAMETOOLONG 36 /* File name too long */　　#define ENOLCK 37 /* No record locks available */　　#define ENOSYS 38 /* Function not implemented */　　#define ENOTEMPTY 39 /* Directory not empty */　　#define ELOOP 40 /* Too many symbolic links encountered */　　#define EWOULDBLOCK EAGAIN /* Operation would block */　　#define ENOMSG 42 /* No message of desired type */　　#define EIDRM 43 /* Identifier removed */　　#define ECHRNG 44 /* Channel number out of range */　　#define EL2NSYNC 45 /* Level 2 not synchronized */　　#define EL3HLT 46 /* Level 3 halted */　　#define EL3RST 47 /* Level 3 reset */　　#define ELNRNG 48 /* Link number out of range */　　#define EUNATCH 49 /* Protocol driver not attached */　　#define ENOCSI 50 /* No CSI structure available */　　#define EL2HLT 51 /* Level 2 halted */　　#define EBADE 52 /* Invalid exchange */　　#define EBADR 53 /* Invalid request descriptor */　　#define EXFULL 54 /* Exchange full */　　#define ENOANO 55 /* No anode */　　#define EBADRQC 56 /* Invalid request code */　　#define EBADSLT 57 /* Invalid slot */　　#define EDEADLOCK EDEADLK　　#define EBFONT 59 /* Bad font file format */　　#define ENOSTR 60 /* Device not a stream */　　#define ENODATA 61 /* No data available */　　#define ETIME 62 /* Timer expired */　　#define ENOSR 63 /* Out of streams resources */　　#define ENONET 64 /* Machine is not on the network */　　#define ENOPKG 65 /* Package not installed */　　#define EREMOTE 66 /* Object is remote */　　#define ENOLINK 67 /* Link has been severed */　　#define EADV 68 /* Advertise error */　　#define ESRMNT 69 /* Srmount error */　　#define ECOMM 70 /* Communication error on send */　　#define EPROTO 71 /* Protocol error */　　#define EMULTIHOP 72 /* Multihop attempted */　　#define EDOTDOT 73 /* RFS specific error */　　#define EBADMSG 74 /* Not a data message */　　#define EOVERFLOW 75 /* Value too large for defined data type */　　#define ENOTUNIQ 76 /* Name not unique on network */　　#define EBADFD 77 /* File descriptor in bad state */　　#define EREMCHG 78 /* Remote address changed */　　#define ELIBACC 79 /* Can not access a needed shared library */　　#define ELIBBAD 80 /* Accessing a corrupted shared library */　　#define ELIBSCN 81 /* .lib section in a.out corrupted */　　#define ELIBMAX 82 /* Attempting to link in too many shared libraries */　　#define ELIBEXEC 83 /* Cannot exec a shared library directly */　　#define EILSEQ 84 /* Illegal byte sequence */　　#define ERESTART 85 /* Interrupted system call should be restarted */　　#define ESTRPIPE 86 /* Streams pipe error */　　#define EUSERS 87 /* Too many users */　　#define ENOTSOCK 88 /* Socket operation on non-socket */　　#define EDESTADDRREQ 89 /* Destination address required */　　#define EMSGSIZE 90 /* Message too long */　　#define EPROTOTYPE 91 /* Protocol wrong type for socket */　　#define ENOPROTOOPT 92 /* Protocol not available */　　#define EPROTONOSUPPORT 93 /* Protocol not supported */　　#define ESOCKTNOSUPPORT 94 /* Socket type not supported */　　#define EOPNOTSUPP 95 /* Operation not supported on transport endpoint */　　#define EPFNOSUPPORT 96 /* Protocol family not supported */　　#define EAFNOSUPPORT 97 /* Address family not supported by protocol */　　#define EADDRINUSE 98 /* Address already in use */　　#define EADDRNOTAVAIL 99 /* Cannot assign requested address */　　#define ENETDOWN 100 /* Network is down */　　#define ENETUNREACH 101 /* Network is unreachable */　　#define ENETRESET 102 /* Network dropped connection because of reset */　　#define ECONNABORTED 103 /* Software caused connection abort */　　#define ECONNRESET 104 /* Connection reset by peer */　　#define ENOBUFS 105 /* No buffer space available */　　#define EISCONN 106 /* Transport endpoint is already connected */　　#define ENOTCONN 107 /* Transport endpoint is not connected */　　#define ESHUTDOWN 108 /* Cannot send after transport endpoint shutdown */　　#define ETOOMANYREFS 109 /* Too many references: cannot splice */　　#define ETIMEDOUT 110 /* Connection timed out */　　#define ECONNREFUSED 111 /* Connection refused */　　#define EHOSTDOWN 112 /* Host is down */　　#define EHOSTUNREACH 113 /* No route to host */　　#define EALREADY 114 /* Operation already in progress */　　#define EINPROGRESS 115 /* Operation now in progress */　　#define ESTALE 116 /* Stale NFS file handle */　　#define EUCLEAN 117 /* Structure needs cleaning */　　#define ENOTNAM 118 /* Not a XENIX named type file */　　#define ENAVAIL 119 /* No XENIX semaphores available */　　#define EISNAM 120 /* Is a named type file */　　#define ENOKEY 126 /* Required key not available */　　#define EKEYEXPIRED 127 /* Key has expired */　　#define EKEYREVOKED 128 /* Key has been revoked */　　#define EKEYREJECTED 129 /* Key was rejected by service */　　#define EOWNERDEAD 130 /* Owner died */　　#define ENOTRECOVERABLE 131 /* State not recoverable */　　#define ERFKILL 132 /* Operation not possible due to RF-kill */　　#define EHWPOISON 133 /* Memory page has hardware error */