Gossmap topology compression and helper

Makefile

@@ -658,7 +658,7 @@ $(ALL_TEST_PROGRAMS) $(ALL_FUZZ_TARGETS): %: %.o
 # uses some ccan modules internally).  We want to rely on -lwallycore etc.
 # (as per EXTERNAL_LDLIBS) so we filter them out here.
 $(ALL_PROGRAMS) $(ALL_TEST_PROGRAMS):
-	@$(call VERBOSE, "ld $@", $(LINK.o) $(filter-out %.a,$^) $(LOADLIBES) $(EXTERNAL_LDLIBS) $(LDLIBS) libccan.a -o $@)
+	@$(call VERBOSE, "ld $@", $(LINK.o) $(filter-out %.a,$^) $(LOADLIBES) $(EXTERNAL_LDLIBS) $(LDLIBS) libccan.a $($(@)_LDLIBS) -o $@)
 
 # We special case the fuzzing target binaries, as they need to link against libfuzzer,
 # which brings its own main().

configure

@@ -367,6 +367,20 @@ trap "rm -f $CONFIG_VAR_FILE.$$" 0
 
 $CONFIGURATOR --extra-tests --autotools-style --var-file=$CONFIG_VAR_FILE.$$ --header-file=$CONFIG_HEADER.$$ --configurator-cc="$CONFIGURATOR_CC" --wrapper="$CONFIGURATOR_WRAPPER" "$CC" ${CWARNFLAGS-$BASE_WARNFLAGS} $CDEBUGFLAGS $COPTFLAGS $CSANFLAGS -I$CPATH -L$LIBRARY_PATH $SQLITE3_CFLAGS $POSTGRES_INCLUDE <<EOF
 
+var=HAVE_ZLIB
+desc=zlib support
+style=DEFINES_EVERYTHING|EXECUTE|MAY_NOT_COMPILE
+link=-lz
+code=
+#include <zlib.h>
+#include <stdlib.h>
+
+int main(void)
+{
+	gzFile f = gzopen("/dev/null", "wb");
+	return f != NULL ? 0 : 1;
+}
+/*END*/
 var=HAVE_GOOD_LIBSODIUM
 desc=libsodium with IETF chacha20 variants
 style=DEFINES_EVERYTHING|EXECUTE|MAY_NOT_COMPILE

devtools/Makefile

@@ -1,4 +1,4 @@
-DEVTOOLS := devtools/bolt11-cli devtools/decodemsg devtools/onion devtools/dump-gossipstore devtools/gossipwith devtools/create-gossipstore devtools/mkcommit devtools/mkfunding devtools/mkclose devtools/mkgossip devtools/mkencoded devtools/mkquery devtools/lightning-checkmessage devtools/topology devtools/route devtools/bolt12-cli devtools/encodeaddr devtools/features devtools/fp16 devtools/rune
+DEVTOOLS := devtools/bolt11-cli devtools/decodemsg devtools/onion devtools/dump-gossipstore devtools/gossipwith devtools/create-gossipstore devtools/mkcommit devtools/mkfunding devtools/mkclose devtools/mkgossip devtools/mkencoded devtools/mkquery devtools/lightning-checkmessage devtools/topology devtools/route devtools/bolt12-cli devtools/encodeaddr devtools/features devtools/fp16 devtools/rune devtools/gossmap-compress
 ifeq ($(HAVE_SQLITE3),1)
 DEVTOOLS += devtools/checkchannels
 endif
@@ -11,6 +11,11 @@ ALL_C_SOURCES += $(DEVTOOLS_TOOL_SRC)
 ALL_C_HEADERS +=
 ALL_PROGRAMS += $(DEVTOOLS)
 
+# gossmap-compress wants -lz if we say we have it.
+ifeq ($(HAVE_ZLIB),1)
+devtools/gossmap-compress_LDLIBS=-lz
+endif # ZLIB
+
 DEVTOOLS_COMMON_OBJS :=				\
 	common/amount.o				\
 	common/autodata.o			\
@@ -57,6 +62,8 @@ devtools/bolt11-cli: $(DEVTOOLS_COMMON_OBJS) $(JSMN_OBJS) $(BITCOIN_OBJS) wire/f
 
 devtools/encodeaddr: common/utils.o common/bech32.o devtools/encodeaddr.o
 
+devtools/gossmap-compress: $(DEVTOOLS_COMMON_OBJS) $(BITCOIN_OBJS) wire/fromwire.o wire/towire.o wire/tlvstream.o common/gossmap.o common/fp16.o devtools/gossmap-compress.o gossipd/gossip_store_wiregen.o
+
 devtools/bolt12-cli: $(DEVTOOLS_COMMON_OBJS) $(BITCOIN_OBJS) wire/bolt12_wiregen.o wire/fromwire.o wire/towire.o common/bolt12.o common/bolt12_merkle.o devtools/bolt12-cli.o common/setup.o common/iso4217.o
 
 devtools/decodemsg: $(DEVTOOLS_COMMON_OBJS) $(JSMN_OBJS) $(BITCOIN_OBJS) $(WIRE_PRINT_OBJS) wire/fromwire.o wire/towire.o devtools/print_wire.o devtools/decodemsg.o