Add support for fuzzing using cargo fuzz

I've been fuzzing seq_io, and found an issue. With this PR applied, run

env RUST_BACKTRACE=1 cargo fuzz run single_thread -- -max_len=100 -only_ascii=1

I'm getting a panic:

``` INFO: Seed: 3182441194 INFO: Loaded 1 modules (1091157 guards): 1091157 [0x109391148, 0x1097baa9c), INFO: 76 files found in /Users/adrianseyboldt/git/seq_io/fuzz/corpus/single_thread INFO: seed corpus: files: 76 min: 1b max: 100b total: 3390b rss: 50Mb #77 INITED cov: 3516 ft: 6385 corp: 28/615b exec/s: 0 rss: 67Mb #98 REDUCE cov: 3516 ft: 6385 corp: 28/601b exec/s: 0 rss: 68Mb L: 18/82 MS: 1 EraseBytes- thread '' panicked at 'slice index starts at 1 but ends at 0', libcore/slice/mod.rs:1941:5 stack backtrace: 0: std::sys::unix::backtrace::tracing::imp::unwind_backtrace at libstd/sys/unix/backtrace/tracing/gcc_s.rs:49 1: std::sys_common::backtrace::print at libstd/sys_common/backtrace.rs:71 at libstd/sys_common/backtrace.rs:59 2: std::panicking::default_hook::{{closure}} at libstd/panicking.rs:211 3: std::panicking::default_hook at libstd/panicking.rs:227 4: as core::panic::BoxMeUp>::get at libstd/panicking.rs:475 5: std::panicking::continue_panic_fmt at libstd/panicking.rs:390 6: std::panicking::default_hook::{{closure}} at libstd/panicking.rs:325 7: core::ptr::drop_in_place at libcore/panicking.rs:77 8: core::ptr::drop_in_place at libcore/slice/mod.rs:1941 9: core::alloc::Layout::align at /Users/travis/build/rust-lang/rust/src/libcore/slice/mod.rs:2098 10: core::str::traits::::eq at /Users/travis/build/rust-lang/rust/src/libcore/slice/mod.rs:1917 11: seq_io::fastq::BufferPosition::head at ./src/fastq.rs:750 12: >::get_error_pos at ./src/fastq.rs:322 13: >::next_complete at ./src/fastq.rs:368 14: >::proceed at ./src/fastq.rs:119 15: >::next at ./src/fastq.rs:142 16: asan.module_dtor at fuzz_targets/single_thread.rs:15 17: libfuzzer_sys::test_input_wrap::{{closure}} at /Users/adrianseyboldt/.cargo/git/checkouts/libfuzzer-sys-e07fde05820d7bc6/86bcaac/src/lib.rs:11 18: asan.module_dtor at /Users/travis/build/rust-lang/rust/src/libstd/panicking.rs:310 ==71378== ERROR: libFuzzer: deadly signal #0 0x10b582bf7 in __sanitizer_print_stack_trace (libclang_rt.asan_osx_dynamic.dylib:x86_64+0x62bf7) #1 0x108fa7cfb in fuzzer::Fuzzer::CrashCallback() FuzzerLoop.cpp:233 #2 0x108fa7cad in fuzzer::Fuzzer::StaticCrashSignalCallback() FuzzerLoop.cpp:206 #3 0x109005ea7 in fuzzer::CrashHandler(int, __siginfo*, void*) FuzzerUtilPosix.cpp:36 #4 0x7fff6d803f59 in _sigtramp (libsystem_platform.dylib:x86_64+0x1f59) #5 0x109304007 (single_thread):x86_64+0x102a0f007) #6 0x7fff6d5a11ad in abort (libsystem_c.dylib:x86_64+0x5d1ad) #7 0x109055318 in panic_abort::__rust_start_panic::abort::h634520f98782cd18 lib.rs:61 #8 0x109055308 in __rust_start_panic lib.rs:56 #9 0x109049e28 in rust_panic panicking.rs:523 #10 0x109049e01 in std::panicking::rust_panic_with_hook::h63bac89c0b130b1b panicking.rs:495 #11 0x10904990c in std::panicking::continue_panic_fmt::hca36ebb6f3aa63ac panicking.rs:390 #12 0x1090497f8 in rust_begin_unwind panicking.rs:325 #13 0x1090644e1 in core::panicking::panic_fmt::hf13b65b6154af8d5 panicking.rs:77 #14 0x109057ff4 in core::slice::slice_index_order_fail::h43a32eb72008320c mod.rs:1941 #15 0x108f2e66e in _$LT$core..ops..range..Range$LT$usize$GT$$u20$as$u20$core..slice..SliceIndex$LT$$u5b$T$u5d$$GT$$GT$::index::h0faf9fbc7c59c6ff mod.rs:2098 #16 0x1089b1695 in core::slice::_$LT$impl$u20$core..ops..index..Index$LT$I$GT$$u20$for$u20$$u5b$T$u5d$$GT$::index::h18f44fda58e6d108 mod.rs:1917 #17 0x106918df2 in seq_io::fastq::BufferPosition::head::h255a495d6fa69647 fastq.rs:750 #18 0x106901a4c in _$LT$seq_io..fastq..Reader$LT$R$C$$u20$S$GT$$GT$::get_error_pos::hb03a14f6d76fb403 fastq.rs:322 #19 0x106904db7 in _$LT$seq_io..fastq..Reader$LT$R$C$$u20$S$GT$$GT$::next_complete::hc1c47ae20e64b998 fastq.rs:368 #20 0x106911419 in _$LT$seq_io..fastq..Reader$LT$R$C$$u20$S$GT$$GT$::proceed::hc5c2d0ce376e739b fastq.rs:119 #21 0x10690fa5f in _$LT$seq_io..fastq..Reader$LT$R$C$$u20$S$GT$$GT$::next::h131e1813100d008b fastq.rs:142 #22 0x1068fbabf in rust_fuzzer_test_input single_thread.rs:15 #23 0x108fa42de in libfuzzer_sys::test_input_wrap::_$u7b$$u7b$closure$u7d$$u7d$::h0a71f7a9044d8747 lib.rs:11 #24 0x108fa56e0 in std::panicking::try::do_call::h6dffe5f7048c2351 panicking.rs:310 #25 0x1090552fb in __rust_maybe_catch_panic lib.rs:39 #26 0x108fa4c12 in std::panicking::try::hee4100871ea2e35d panicking.rs:289 #27 0x108fa018f in std::panic::catch_unwind::h02670d829b3a0291 panic.rs:392 #28 0x108fa3b01 in LLVMFuzzerTestOneInput lib.rs:9 #29 0x108faa811 in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) FuzzerLoop.cpp:515 #30 0x108fa9c6a in fuzzer::Fuzzer::RunOne(unsigned char const*, unsigned long, bool, fuzzer::InputInfo*, bool*) FuzzerLoop.cpp:440 #31 0x108faff03 in fuzzer::Fuzzer::MutateAndTestOne() FuzzerLoop.cpp:648 #32 0x108fb27d8 in fuzzer::Fuzzer::Loop(std::__1::vector, std::__1::allocator >, fuzzer::fuzzer_allocator, std::__1::allocator > > > const&) FuzzerLoop.cpp:775 #33 0x108ff1961 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) FuzzerDriver.cpp:754 #34 0x10901e87f in main FuzzerMain.cpp:20 #35 0x7fff6d4f5014 in start (libdyld.dylib:x86_64+0x1014) NOTE: libFuzzer has rudimentary signal handlers. Combine libFuzzer with AddressSanitizer or similar for better crash reports. SUMMARY: libFuzzer: deadly signal MS: 3 EraseBytes-CopyPart-EraseBytes-; base unit: d95527d899043c4adbc0db32a303b7221f1f05d5 0xa,0x2a, \x0a* artifact_prefix='/Users/adrianseyboldt/git/seq_io/fuzz/artifacts/single_thread/'; Test unit written to /Users/adrianseyboldt/git/seq_io/fuzz/artifacts/single_thread/crash-f9583eb831f52cfe1fd177744a6b511382ab8df6 Base64: Cio= ```

I'm the fastq-rs author by the way. I love what you've been doing with seq_io. :-)

markschl / seq_io

Add support for fuzzing using cargo fuzz #2