AddressSanitizer: heap-buffer-overflow at lexer.hpp

[rainoftime]

Git commit id

6e7ab5576391

POC
case1.txt

Describe the bug

Steps to reproduce the behavior:

1. run ./tester $f where libsass is compiled with AddressSanitizer.
2. the program crashes with the backtrace like:

For case1.txt

==31962==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60f0000000e5 at pc 0x000001383bbc bp 0x7fffeb71e9d0 sp 0x7fffeb71e9c8
READ of size 1 at 0x60f0000000e5 thread T0
    #0 0x1383bbb in char const* Sass::Prelexer::exactly<(char)92>(char const*) /workdir/MemLock/evaluation/BUILD/libsass/SRC_MemLock/src/./lexe
r.hpp:82:14
    #1 0x140ad8e in char const* Sass::Prelexer::sequence<&(char const* Sass::Prelexer::exactly<(char)92>(char const*)), &Sass::Prelexer::re_lin
ebreak>(char const*) /workdir/MemLock/evaluation/BUILD/libsass/SRC_MemLock/src/./lexer.hpp:216:20
    #2 0x140a94c in char const* Sass::Prelexer::alternatives<&(char const* Sass::Prelexer::sequence<&(char const* Sass::Prelexer::exactly<(char
)92>(char const*)), &Sass::Prelexer::re_linebreak>(char const*)), &Sass::Prelexer::escape_seq, &Sass::Prelexer::unicode_seq, &Sass::Prelexer::i
nterpolant, &(char const* Sass::Prelexer::any_char_but<(char)39>(char const*))>(char const*) /workdir/MemLock/evaluation/BUILD/libsass/SRC_MemL
ock/src/./lexer.hpp:200:19
......

Desktop (please complete the following information):

• OS: Ubuntu 16.04.2 LTS
• Compiler & Version: Clang-6.0.1
• Compilation mode and/or compiler flags: "-O0, -fsanitize=address,undefined"

[xzyfer]

Minimal reproduction
test.scss.zip