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Set up your Tor to offer a hidden service, and use a hostname destination, like localhost:80, on the HiddenServicePort line.

Then ifdown eth0 so you have no network.

Then run valgrind tor --verify-config

and voila, you get this complaint:

Configuration was valid
==31082== Invalid free() / delete / delete[] / realloc()
==31082==    at 0x4C29E90: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==31082==    by 0x63A116B: __libc_freeres (in /lib/x86_64-linux-gnu/libc-2.19.so)
==31082==    by 0x4A236CC: _vgnU_freeres (in /usr/lib/valgrind/vgpreload_core-amd64-linux.so)
==31082==    by 0x628CAEA: __run_exit_handlers (exit.c:97)
==31082==    by 0x628CB74: exit (exit.c:104)
==31082==    by 0x6276B4B: (below main) (libc-start.c:321)
==31082==  Address 0x65fa2d0 is 0 bytes inside data symbol "noai6ai_cached"

If you leave off the --verify-config, you can trigger the same thing, by starting, and then after a while ctrl-C'ing your Tor so it exits, at which point you get something similar:

==8895== Invalid free() / delete / delete[] / realloc()
==8895==    at 0x4C29E90: free (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==8895==    by 0x63A116B: __libc_freeres (in /lib/x86_64-linux-gnu/libc-2.19.so)
==8895==    by 0x4A236CC: _vgnU_freeres (in /usr/lib/valgrind/vgpreload_core-amd64-linux.so)
==8895==    by 0x628CAEA: __run_exit_handlers (exit.c:97)
==8895==    by 0x628CB74: exit (exit.c:104)
==8895==    by 0x154686: process_signal (main.c:2601)
==8895==    by 0x154686: signal_callback (main.c:2583)
==8895==    by 0x5361A14: event_base_loop (in /usr/lib/x86_64-linux-gnu/libevent-2.0.so.5.1.9)
==8895==    by 0x152B53: run_main_loop_once (main.c:2514)
==8895==    by 0x152B53: run_main_loop_until_done (main.c:2568)
==8895==    by 0x152B53: do_main_loop (main.c:2481)
==8895==    by 0x1562B4: tor_main (main.c:3628)
==8895==    by 0x14E408: main (tor_main.c:34)
==8895==  Address 0x65fa2d0 is 0 bytes inside data symbol "noai6ai_cached"

It's not clear to me what is going wrong.