Use -ffunction-sections to build smaller binaries

Makefile

@@ -313,6 +313,10 @@ else
 LDLIBS = -L$(CPATH) -lm $(SQLITE3_LDLIBS) $(COVFLAGS)
 endif
 
+ifeq ($(HAVE_FUNCTION_SECTIONS),1)
+LDLIBS += -Wl,--gc-sections
+endif
+
 # If we have the postgres client library we need to link against it as well
 ifeq ($(HAVE_POSTGRES),1)
 LDLIBS += $(POSTGRES_LDLIBS)
@@ -1152,7 +1156,8 @@ ccan-rune-rune.o: $(CCANDIR)/ccan/rune/rune.c
 ccan-rune-coding.o: $(CCANDIR)/ccan/rune/coding.c
 	@$(call VERBOSE, "cc $<", $(CC) $(CFLAGS) -c -o $@ $<)
 
-print-binary-sizes: $(ALL_PROGRAMS) $(ALL_TEST_PROGRAMS)
-	@find $(ALL_PROGRAMS) $(ALL_TEST_PROGRAMS) -printf '%p\t%s\n'
-	@echo 'Total program size:	'`find $(ALL_PROGRAMS) -printf '%s\n' | awk '{TOTAL+= $$1} END {print TOTAL}'`
-	@echo 'Total tests size:	'`find $(ALL_TEST_PROGRAMS) -printf '%s\n' | awk '{TOTAL+= $$1} END {print TOTAL}'`
+print-binary-sizes: $(ALL_PROGRAMS) $(ALL_TEST_PROGRAMS) $(BIN_PROGRAMS)
+	@echo User programs:
+	@size -t $(PKGLIBEXEC_PROGRAMS) $(filter-out tools/reckless,$(BIN_PROGRAMS)) $(PLUGINS)
+	@echo All programs:
+	@size -t $(ALL_PROGRAMS) $(ALL_TEST_PROGRAMS) | tail -n1

configure

@@ -202,7 +202,6 @@ set_defaults()
 	FUZZFLAGS="-fsanitize=fuzzer-no-link -DFUZZING_BUILD_MODE_UNSAFE_FOR_PRODUCTION"
 	CSANFLAGS="$CSANFLAGS $FUZZFLAGS"
     fi
-    echo CSANFLAGS = $CSANFLAGS
     PYTHON=${PYTHON-$(default_python)}
     SED=${SED-$(default_sed)}
     PYTEST=${PYTEST-$(default_pytest $PYTHON)}
@@ -213,6 +212,17 @@ set_defaults()
     RUST=${RUST:-$(default_rust_setting)}
 }
 
+# Given CC and FLAGS do we support -ffunction-sections and --gc-sections?
+have_function_sections()
+{
+    # This gets removed automatically on exit!
+    TMPCFILE=$CONFIG_VAR_FILE.$$.c
+    TMPOBJFILE=$CONFIG_VAR_FILE.$$.o
+
+    echo "int foo(void); int foo(void) { return 0; }" > $TMPCFILE
+    $1 $2 -ffunction-sections -Wl,--gc-sections -c $TMPCFILE -o $TMPOBJFILE
+}
+
 usage()
 {
     echo "Usage: ./configure [--reconfigure] [setting=value] [options]"
@@ -355,10 +365,19 @@ EOF
     done
 fi
 
+# We call this first, so we can make sure configurator runs with it as a sanity check!
+if have_function_sections $CC "${CWARNFLAGS-$BASE_WARNFLAGS} $CDEBUGFLAGS $COPTFLAGS"; then
+    HAVE_FUNCTION_SECTIONS=1
+    LDFLAGS="-Wl,--gc-sections"
+    COPTFLAGS="$COPTFLAGS -ffunction-sections"
+else
+    HAVE_FUNCTION_SECTIONS=0
+    LDFLAGS=
+fi
 
 # We assume warning flags don't affect congfigurator that much!
 echo -n "Compiling $CONFIGURATOR..."
-$CC ${CWARNFLAGS-$BASE_WARNFLAGS} $CDEBUGFLAGS $COPTFLAGS -o $CONFIGURATOR $CONFIGURATOR.c
+$CC ${CWARNFLAGS-$BASE_WARNFLAGS} $CDEBUGFLAGS $COPTFLAGS $LDFLAGS -o $CONFIGURATOR $CONFIGURATOR.c
 echo "done"
 
 if [ "$CLANG_COVERAGE" = "1" ]; then
@@ -406,7 +425,7 @@ if command -v "${PG_CONFIG}" >/dev/null; then
 fi
 
 # Clean up on exit.
-trap "rm -f $CONFIG_VAR_FILE.$$" 0
+trap "rm -f $CONFIG_VAR_FILE.$$*" 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 $SODIUM_CFLAGS $POSTGRES_INCLUDE <<EOF
 
@@ -619,6 +638,7 @@ add_var FUZZING "$FUZZING"
 add_var RUST "$RUST"
 add_var PYTHON "$PYTHON"
 add_var SED "$SED"
+add_var HAVE_FUNCTION_SECTIONS "$HAVE_FUNCTION_SECTIONS"
 
 # Hack to avoid sha256 name clash with libwally: will be fixed when that
 # becomes a standalone shared lib.