AddressSanitizer: negative-size-param in addRule

[cx104906]

Can reproduce with clang but can not reproduce by gcc.
Unclear whether this is a bug in liblouis or a bug in Clang.
reproduce in docker:

docker pull ubuntu:20.04
docker run --name test -it --privileged=true --net=host ubuntu:20.04
apt update
apt install git clang gcc g++ autoconf automake libtool build-essential pkg-config -y
git clone https://github.com/liblouis/liblouis.git
./autogen.sh
CC=clang CXX=clang++ CFLAGS="-fsanitize=address -g -fPIC -O0" CXXFLAGS="-fsanitize=address -g -fPIC -O0" ./configure --enable-static --disable-shared
make
git clone https://github.com/cx104906/poc.git
./tools/lou_checktable poc/lou_checktable/id1

ASAN says:

root@cas-PC:/liblouis# ./tools/lou_checktable poc/lou_checktable/id1
poc/lou_checktable/id1:1: error: invalid escape sequence '\ '
poc/lou_checktable/id1:2: warning: invalid UTF-8. Assuming Latin-1.
poc/lou_checktable/id1:2: warning: invalid UTF-8. Assuming Latin-1.
poc/lou_checktable/id1:2: error: liblouis has not been compiled for 32-bit Unicode
=================================================================
==22623==ERROR: AddressSanitizer: negative-size-param: (size=-2)
    #0 0x492e47 in __asan_memcpy (/liblouis/tools/lou_checktable+0x492e47)
    #1 0x4ed6ea in addRule /liblouis/liblouis/compileTranslationTable.c:1039:3
    #2 0x4f65e8 in compileSwap /liblouis/liblouis/compileTranslationTable.c:1668:7
    #3 0x4e557f in compileRule /liblouis/liblouis/compileTranslationTable.c:4301:11
    #4 0x4d0a78 in compileFile /liblouis/liblouis/compileTranslationTable.c:4869:9
    #5 0x4cb61d in compileTable /liblouis/liblouis/compileTranslationTable.c:4991:9
    #6 0x4c98ce in getTable /liblouis/liblouis/compileTranslationTable.c:5164:7
    #7 0x4c8ca3 in _lou_getTable /liblouis/liblouis/compileTranslationTable.c:5073:2
    #8 0x4caef8 in lou_getTable /liblouis/liblouis/compileTranslationTable.c:5085:2
    #9 0x4c36a4 in main /liblouis/tools/lou_checktable.c:115:16
    #10 0x7ffff7c58082 in __libc_start_main (/lib/x86_64-linux-gnu/libc.so.6+0x24082)
    #11 0x41b31d in _start (/liblouis/tools/lou_checktable+0x41b31d)

Address 0x7ffffffe3df2 is located in stack of thread T0 at offset 4402 in frame
    #0 0x4f5fff in compileSwap /liblouis/liblouis/compileTranslationTable.c:1648

  This frame has 6 object(s):
    [32, 4130) 'ruleChars' (line 1649)
    [4400, 8498) 'ruleDots' (line 1650) <== Memory access at offset 4402 is inside this variable
    [8768, 12866) 'name' (line 1651)
    [13136, 17234) 'matches' (line 1652)
    [17504, 21602) 'replacements' (line 1653)
    [21872, 21876) 'ruleOffset' (line 1654)
HINT: this may be a false positive if your program uses some custom stack unwind mechanism, swapcontext or vfork
      (longjmp and C++ exceptions *are* supported)
SUMMARY: AddressSanitizer: negative-size-param (/liblouis/tools/lou_checktable+0x492e47) in __asan_memcpy
==22623==ABORTING