关于fopen电话的SIGABRT

Question

我正在编写一段代码来检查文件是否存在.当用户传入一个只带有名称(没有斜杠)的文件参数时,我将使用PATH环境变量中的路径检查文件是否存在.我正在使用gcc编译Ubuntu并且一直在使用gdb.我发现导致SIGABRT的那条线但不确定信息告诉我什么.这是我第一次使用gdb.这是我的片段:

char* PATH = NULL;
PATH = (char*)getenv( "PATH" );
char* pathtoken = strtok( PATH, ":" );
int index = 0;

while ( pathtoken != NULL )
{
    index++;
    printf( "%s\n", pathtoken );
    char* pathdir = (char*)malloc( sizeof(pathtoken) );
    strcpy( pathdir, pathtoken );
    GetFullPath( pathdir, filename );
    inputstream = fopen( pathdir, "r" );

    if ( inputstream != NULL)
    {
        free( pathdir );
        break;
        }

        free( pathdir );
        pathtoken = strtok( NULL, ":" );
    }

char* GetFullPath( char* dirpath, char* filename )
{
    //Append back slash
    int len = strlen(dirpath);
    dirpath[len] = '/';
    dirpath[len+1] = '\0';

    return strcat( dirpath, filename );
}

它发生在fopen线的第一次迭代中.这是我的gdb输出

启动程序:/home/seapoe/Documents/OsClass/CodePractice/a.out text1/usr/lib/lightdm/lightdm

断点1,main(argc = 2,argv = 0xbffff3a4)位于xssh.c:87

87 GetFullPath(pathdir,filename);

(gdb)接下来

89 inputstream = fopen(pathdir,"r");

(gdb)print pathdir

$ 5 = 0x804c008"/ usr/lib/lightdm/lightdm/text1"

(gdb)print pathdir [strlen(pathdir)]

$ 6 = 0'\ 000'

(gdb)print pathdir [strlen(pathdir)+1]

$ 7 = 0'\ 000'

(gdb)print pathdir [strlen(pathdir)+2]

$ 8 = 0'\ 000'

(gdb)print pathdir [strlen(pathdir)-1]

$ 9 = 49'1'

(gdb)接下来

*检测到glibc /home/seapoe/Documents/OsClass/CodePractice/a.out:free():下一个大小无效(正常):0x0804c018**

======= Backtrace:=========

/lib/i386-linux-gnu/libc.so.6(+0x75ee2)[0xb7e97ee2]

/lib/i386-linux-gnu/libc.so.6(+0x65db5)[0xb7e87db5]

/lib/i386-linux-gnu/libc.so.6(fopen+0x2b)[0xb7e87deb]

/home/seapoe/Documents/OsClass/CodePractice/a.out[0x8048a77]

/lib/i386-linux-gnu/libc.so.6(__libc_start_main+0xf3)[0xb7e3b4d3]

/home/seapoe/Documents/OsClass/CodePractice/a.out[0x8048771]

=======内存映射:========

08048000-0804a000 r-xp 00000000 08:01 536263/home/seapoe/Documents/OsClass /CodePractice/a.out

0804a000-0804b000 r - p 00001000 08:01 536263 /home/seapoe/Documents/OsClass/CodePractice/a.out

0804b000-0804c000 rw-p 00002000 08:01 536263 /home/seapoe/Documents/OsClass/CodePractice/a.out

0804c000-0806d000 rw-p 00000000 00:00 0 [堆]

b7df3000-b7e0f000 r-xp 00000000 08:01 394136 /lib/i386-linux-gnu/libgcc_s.so.1

b7e0f000-b7e10000 r - p 0001b000 08:01 394136 /lib/i386-linux-gnu/libgcc_s.so.1

b7e10000-b7e11000 rw-p 0001c000 08:01 394136 /lib/i386-linux-gnu/libgcc_s.so.1

b7e21000-b7e22000 rw-p 00000000 00:00 0

b7e22000-b7fc5000 r-xp 00000000 08:01 394115 /lib/i386-linux-gnu/libc-2.15.so

b7fc5000-b7fc7000 r - p 001a3000 08:01 394115 /lib/i386-linux-gnu/libc-2.15.so

b7fc7000-b7fc8000 rw-p 001a5000 08:01 394115 /lib/i386-linux-gnu/libc-2.15.so

b7fc8000-b7fcb000 rw-p 00000000 00:00 0

b7fd9000-b7fdd000 rw-p 00000000 00:00 0

b7fdd000-b7fde000 r-xp 00000000 00:00 0 [vdso]

b7fde000-b7ffe000 r-xp 00000000 08:01 394095 /lib/i386-linux-gnu/ld-2.15.so

b7ffe000-b7fff000 r - p 0001f000 08:01 394095 /lib/i386-linux-gnu/ld-2.15.so

b7fff000-b8000000 rw-p 00020000 08:01 394095 /lib/i386-linux-gnu/ld-2.15.so

bffdf000-c0000000 rw-p 00000000 00:00 0 [stack]

程序接收信号SIGABRT,已中止.

__kernel_vsyscall()中的0xb7fdd424

调用GetFullPath后,您可以看到在fopen调用之前返回有效路径

Answer 1

char* pathdir = (char*)malloc( sizeof(pathtoken) );

是错的.sizeof(pathtoken)将为您提供系统上指针的大小(4或8).你要

pathdir = strdup(pathtoken)

这也是错误的,因为你试图追加它.只需使pathdir成为MAX_PATH(或PATH_MAX,取决于您的操作系统)长度的char数组.