我无法使用 gdb 访问/打印结构中整数字段的值。它说无法访问地址。我确定这不是空指针问题。那么这可能是什么原因呢？ 任何内存损坏问题？如果是，那么现在如何处理？如何知道根本原因？
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Attaching to process 445266
[New LWP 445267]
[New LWP 445268]
[New LWP 445269]
[New LWP 445270]
[New LWP 445271]
[New LWP 445290]
[New LWP 445291]
[New LWP 445292]
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
warning: Target and debugger are in different PID namespaces; thread lists and other data are likely unreliable. Connect to gdbserver inside the container.
__pthread_clockjoin_ex (threadid=139864192313088, thread_return=0x0, clockid=<optimized out>, abstime=<optimized out>, block=<optimized out>) at pthread_join_common.c:145
145 pthread_join_common.c: No such file or directory.
(gdb) n
Thread 7 "e2" received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7f34ab7fe700 (LWP 445290)]
0x00007f34b4c38792 in SIsendt (gptr=0x55b38b2f1060, fd=15, ubuf=0x7f347a2f4830 " \r", ulen=3360) at /home/ubuntu/office/nearrt-ric-plt/rmr/src/rmr/si/src/si95/sisendt.c:74
74 if( (fd = tpptr->fd) < 0 || (fd = tpptr->fd) >= FD_SETSIZE ) { // fd user given might not be real, and this might be closed already
(gdb) info locals
status = -1
writefds = <error reading variable writefds (Cannot access memory at address 0x7f34ab2bc8c0)>
execpfds = <error reading variable execpfds (Cannot access memory at address 0x7f34ab2bc940)>
tpptr = 0x2
qptr = <optimized out>
time = {tv_sec = 31, tv_usec = 139864186800368}
sidx = 0
(gdb) bt
#0 0x00007f34b4c38792 in SIsendt (gptr=0x55b38b2f1060, fd=15, ubuf=0x7f347a2f4830 <error: Cannot access memory at address 0x7f347a2f4830>, ulen=3360) at /home/ubuntu/office/nearrt-ric-plt/rmr/src/rmr/si/src/si95/sisendt.c:74
#1 0x00007f34b4c320bb in send_msg (ctx=0x55b38b2cfd80, msg=0x7f3490102830, nn_sock=15, retries=1) at /home/ubuntu/office/nearrt-ric-plt/rmr/src/rmr/si/src/sr_si_static.c:619
Backtrace stopped: Cannot access memory at address 0x7f34ab2bca38
(gdb) p tpptr
$1 = (struct tp_blk *) 0x2
(gdb) p gptr
$2 = (struct ginfo_blk *) 0x55b38b2f1060
(gdb) p ubuf
$3 = 0x7f347a2f4830 <error: Cannot access memory at address 0x7f347a2f4830>
(gdb) p tpptr
$4 = (struct tp_blk *) 0x2
(gdb) p *tpptr -----------> tpptr is not null, still can not access memory why?
Cannot access memory at address 0x2
(gdb) p tpptr->fd
Cannot access memory at address 0x12
(gdb) p tpptr ----------> as said already, tpptr is not null
$5 = (struct tp_blk *) 0x2
(gdb)
(gdb) ptype tpptr->fd -----> this is int
type = int
(gdb) p tpptr->fd ---------> why i am not able to access interger
Cannot access memory at address 0x12
(gdb) ptype tpptr
type = struct tp_blk {
struct tp_blk *next;
struct tp_blk *prev;
int fd;
int flags;
int type;
int family;
struct sockaddr *addr;
struct sockaddr *paddr;
int palen;
struct ioq_blk *squeue;
struct ioq_blk *sqtail;
long long qcount;
long long sent;
long long rcvd;
} *
(gdb)
以下是供上述参考的代码片段。请参阅第 74 行
49 extern int SIsendt( struct ginfo_blk *gptr, int fd, char *ubuf, int ulen ) {
50 int status = SI_ERROR; // assume we fail
51 fd_set writefds; // local write fdset to check blockage
52 fd_set execpfds; // exception fdset to check errors
53 struct tp_blk *tpptr; // pointer at the tp_blk for the session
54 struct ioq_blk *qptr; // pointer at i/o queue block
55 struct timeval time; // delay time parameter for select call
56 int sidx = 0; // send index
57
58 errno = EINVAL;
59
60 if( fd < 0 ) {
61 errno = EBADFD;
62 return SI_ERROR; // bad form trying to use this fd
63 }
64
65 if( fd < MAX_FDS ) { // straight from map if possible
66 if ((gptr->tp_map) != NULL) {
67 tpptr = gptr->tp_map[fd];
68 }
69 } else {
70 // list should be locked before traversing
71 for( tpptr = gptr->tplist; tpptr != NULL && tpptr->fd != fd; tpptr = tpptr->next ) ; // find the block if out of map's range
72 }
73 if( tpptr != NULL ) {
74 if( (fd = tpptr->fd) < 0 || (fd = tpptr->fd) >= FD_SETSIZE ) { // fd user given might not be real, and this might be closed already
75 errno = EBADFD;
76 return SI_ERROR;
77 }
78
79 tpptr->sent++; // investigate: this may over count
80
81 FD_ZERO( &writefds ); // clear for select call
82 FD_SET( fd, &writefds ); // set to see if this one was writable
83 FD_ZERO( &execpfds ); // clear and set execptions fdset
84 FD_SET( fd, &execpfds );
85
86 time.tv_sec = 0; // set both to 0 if we just want a poll, else we block at max this amount
87 time.tv_usec = 1; // small pause on check to help drain things