because varstring is an empty string and strlen () is 0, so "strlen () - 1"
is definitely out of the bound of "varstring",
(gdb) bt 10
at /home/yao/SourceCode/gnu/gdb/git/gdb/f-typeprint.c:56
at /home/yao/SourceCode/gnu/gdb/git/gdb/typeprint.c:365
at /home/yao/SourceCode/gnu/gdb/git/gdb/c-valprint.c:650
at /home/yao/SourceCode/gnu/gdb/git/gdb/valprint.c:1236
This patch adds a pre-check that varstring is empty or not.
gdb:
2017-02-27 Yao Qi <yao.qi@linaro.org>
* f-typeprint.c (f_print_type): Check "varstring" is empty first.