Link error : pthread

[Hakkadaikon]

Hi,
When I built nostrdb, the following link error occurred.

$ make clean; make
rm -rf test bench bench-ingest bench-ingest-many
cc -Wall -Wno-misleading-indentation -Wno-unused-function -Werror -O2 -g -Ideps/secp256k1/include -Ideps/lmdb -Ideps/flatcc/include bench.c nostrdb.c sha256.c bech32.c deps/flatcc/src/runtime/json_parser.c deps/flatcc/src/runtime/verifier.c deps/flatcc/src/runtime/builder.c deps/flatcc/src/runtime/emitter.c deps/flatcc/src/runtime/refmap.c deps/lmdb/liblmdb.a deps/secp256k1/.libs/libsecp256k1.a  -o bench
/usr/bin/ld: deps/lmdb/liblmdb.a(mdb.o): in function `mdb_txn_renew0':
/home/hakkadaikon/repos/hakkadaikon/nostrdb/deps/lmdb/mdb.c:2719: undefined reference to `pthread_getspecific'
/usr/bin/ld: /home/hakkadaikon/repos/hakkadaikon/nostrdb/deps/lmdb/mdb.c:2762: undefined reference to `pthread_setspecific'
/usr/bin/ld: deps/lmdb/liblmdb.a(mdb.o): in function `mdb_env_copythr':
/home/hakkadaikon/repos/hakkadaikon/nostrdb/deps/lmdb/mdb.c:9126: undefined reference to `pthread_sigmask'
～
collect2: error: ld returned 1 exit status
make: *** [Makefile:137: bench] Error 1

The problem was resolved by changing nostrdb/Makefile as follows.

--- a/Makefile
+++ b/Makefile
@@ -2,7 +2,7 @@ CFLAGS = -Wall -Wno-misleading-indentation -Wno-unused-function -Werror -O2 -g -
 HEADERS = sha256.h nostrdb.h cursor.h hex.h jsmn.h config.h sha256.h random.h memchr.h $(C_BINDINGS)
 FLATCC_SRCS=deps/flatcc/src/runtime/json_parser.c deps/flatcc/src/runtime/verifier.c deps/flatcc/src/runtime/builder.c deps/flatcc/src/runtime/emitter.c deps/flatcc/src/runtime/refmap.c
 SRCS = nostrdb.c sha256.c bech32.c $(FLATCC_SRCS)
-LDS = $(SRCS) $(ARS) 
+LDS = $(SRCS) $(ARS) -lpthread
 DEPS = $(SRCS) $(HEADERS) $(ARS)
 ARS = deps/lmdb/liblmdb.a deps/secp256k1/.libs/libsecp256k1.a 
 LMDB_VER=0.9.31

I'm using Ubuntu 20.04.

cat /etc/lsb-release
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=20.04
DISTRIB_CODENAME=focal
DISTRIB_DESCRIPTION="Ubuntu 20.04.2 LTS"