gdb program core: don't get the specific bug - gdb

Question

I use gdb command as follows to localize the segmentation fault, but it shows ?? so that I am confused. What does it mean? How to avoid it?
$ gdb program core
...
Program terminated with signal SIGSEGV, Segmentation fault.
#0 0x0000048d0000048c in ?? ()
(gdb) bt
#0 0x0000046a00000469 in ?? ()
#1 0x0000046c0000046b in ?? ()
#2 0x0000046e0000046d in ?? ()
#3 0x000004700000046f in ?? ()
#4 0x0000047300000472 in ?? ()
#5 0x0000047600000475 in ?? ()
#6 0x0000047800000477 in ?? ()
#7 0x0000047a00000479 in ?? ()
#8 0x0000047d0000047b in ?? ()
...
I find that the array is out of bounds and I solved it. But I still confused with the phenomenon above.

Answer 1

0x0000048d0000048c
This looks like you've called a function through a function pointer, but that pointer has been overwritten with two integers: 0x48d == 1165 and 0x48c == 1164 (do these values look like something that your program is using?).
You should use bt to tell you how you got there.
You should probably use Valgrind or Address Sanitizer to check for uninitialized or dangling memory and buffer overflow (which are some of the common ways to end up with invalid function pointer).
Update:
Now that you show the stack trace, it's an almost 100% guarantee that you have some local array of integers which you've overflown (filling it with values like 1129, 1130, 1131, etc.), thus corrupting your stack.
Address Sanitizer (available in recent versions of GCC) should point you straight at where the bug is.

Answer 2

This means that your program crashed in a function unknow by gdb (function not provided by the symbol table)
try these two options, in the given order:
if you are debugging a target, be sure that all your code layers are compiled with the option -g if you are using gcc.
You can give manually the symbol table to gdb with the command file "binary_with_symbol_table" and it will give you the function and the address of the bug.
Note that many exceptions may be hidden behind a segmentation fault.