.
Thread 1 (LWP 8603):
#0  __GI___libc_free (mem=0x1581720) at malloc.c:2968
        ar_ptr = <optimized out>
        p = <optimized out>
        hook = 0
#1  0x00007f1a96aac77a in inflateEnd () from /lib/x86_64-linux-gnu/libz.so.1
No symbol table info available.
#2  0x00007f1a96aa3e68 in ?? () from /lib/x86_64-linux-gnu/libz.so.1
No symbol table info available.
#3  0x00007f1a979d7898 in FileFd::Close() () from /usr/lib/x86_64-linux-gnu/libapt-pkg.so.4.12
No symbol table info available.
#4  0x0000000000403c81 in ?? ()
No symbol table info available.
#5  0x00007f1a97a12b7d in pkgAcqMethod::Run(bool) () from /usr/lib/x86_64-linux-gnu/libapt-pkg.so.4.12
No symbol table info available.
#6  0x0000000000402456 in ?? ()
No symbol table info available.
#7  0x00007f1a970e076d in __libc_start_main (main=0x402330, argc=1, ubp_av=0x7fff362fab48, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fff362fab38) at libc-start.c:226
        result = <optimized out>
        unwind_buf = {cancel_jmp_buf = {{jmp_buf = {0, 3984519707938541963, 4203720, 140734102481728, 0, 0, -3984076195303501429, -3927431842060807797}, mask_was_saved = 0}}, priv = {pad = {0x0, 0x0, 0x405260, 0x7fff362fab48}, data = {prev = 0x0, cleanup = 0x0, canceltype = 4215392}}}
        not_first_call = <optimized out>
#8  0x00000000004024f1 in ?? ()
No symbol table info available.
#9  0x00007fff362fab38 in ?? ()
No symbol table info available.
#10 0x000000000000001c in ?? ()
No symbol table info available.
#11 0x0000000000000001 in ?? ()
No symbol table info available.
#12 0x00007fff362fb46d in ?? ()
No symbol table info available.
#13 0x0000000000000000 in ?? ()
No symbol table info available.