Bug 1429172

Description of problem:
GDB dumps core When escaping a newline with \ in a multiline command.

Version-Release number of selected component (if applicable):
gdb-7.12.1-46.fc25.x86_64

How reproducible:
always

Steps to Reproduce:
1. gdb
2. py
3. print(1);\\
4. print(2)
5. end
6. help

Actual results:
$ gdb 
(gdb) py
>print(1);\
(gdb) print(2)
>end
1
2
help
readline: readline_callback_read_char() called with no handler!
zsh: abort (core dumped)  gdb -q

Expected results:
No core dumping and just the normal (gdb) prompt after enterering the multiline command is finished (plus printing the help  screen).


Additional info:
Entering the `help` command isn't significant - other commands reproduce this as well - even just hitting enter.

This can also reproduced with other multiline commands, e.g.:

$ gdb ls
Reading symbols from ls...Reading symbols from /usr/lib/debug/usr/bin/ls.debug...done.
done.
(gdb) b main
Breakpoint 1 at 0x3990: file ../src/ls.c, line 1347.
(gdb) commands 
Type commands for breakpoint(s) 1, one per line.
End with a line saying just "end".
>silent
>print \
(gdb) argc
>end

readline: readline_callback_read_char() called with no handler!
zsh: abort (core dumped)  gdb -q ls



Escaping newlines in single-line commands works as expected, e.g.:

$ gdb 
(gdb) py print(1);\
print(2)
1
2
(gdb)