The reverse-finish command results in an internal error if it cannot determine
the current function.
(gdb) c
Continuing.
Program received signal SIGSEGV, Segmentation fault.
0x0000000000000000 in ?? ()
(gdb) reverse-finish
Run back to call of #0 0x0000000000000000 in ?? ()
gdb/infcmd.c:1576: internal-error: Finish: couldn't find function.
A problem internal to GDB has been detected,
further debugging may prove unreliable.
Quit this debugging session? (y or n) y
This is not an internal error case since the command may be used in scenarios
where there is no function at the current PC, e.g. after calling through a bad
function pointer.
Turn this into a normal error.
gdb/
* infcmd.c (finish_backward): Turn internal error into normal error.
testsuite/
* gdb.btrace/segv.c: New.
* gdb.btrace/segv.exp: New.
