I read golang official gdb document here https://golang.org/doc/gdb
And I'm curious about what causes question mark when inspecting the stack.
(gdb) bt # backtrace
#0 regexp.TestFind (t=0xf8404a89c0) at /home/user/go/src/regexp/find_test.go:148
#1 0x000000000042f60b in testing.tRunner (t=0xf8404a89c0, test=0x573720) at /home/user/go/src/testing/testing.go:156
#2 0x000000000040df64 in runtime.initdone () at /home/user/go/src/runtime/proc.c:242
#3 0x000000f8404a89c0 in ?? ()
#4 0x0000000000573720 in ?? ()
#5 0x0000000000000000 in ?? ()
So, Is the gdb optimizations caused the question mark? Or what on earth result in such question mark?
One more question, How can I retrieve the message hiden behind question mark?