https://github.com/haampie/libtree/commit/eb56287c1b4eb3b267524ab1e6e31f042b713395

From eb56287c1b4eb3b267524ab1e6e31f042b713395 Mon Sep 17 00:00:00 2001
From: Florian Weimer <fweimer@redhat.com>
Date: Sun, 15 Jan 2023 22:49:37 +0100
Subject: [PATCH] Avoid implicit function declarations in tests (#84)

Future compilers are likely to reject implicit function declarations
by default, causing these tests to fail.  Also replace () with (void)
where appropriate in the changed tests.
--- a/tests/01_origin/Makefile
+++ b/tests/01_origin/Makefile
@@ -7,13 +7,13 @@ LD_LIBRARY_PATH=
 all: check
 
 liba.so: 
-	echo 'int f(){return 1;}' | $(CC) -shared -Wl,-soname,$@ -o $@ -nostdlib -x c -
+	echo 'int f(void){return 1;}' | $(CC) -shared -Wl,-soname,$@ -o $@ -nostdlib -x c -
 
 exe_rpath: liba.so
-	echo 'int _start(){return f();}' | $(CC) -o $@ -Wl,--no-as-needed -Wl,--disable-new-dtags '-Wl,-rpath,$$ORIGIN' -Wno-implicit-function-declaration -nostdlib liba.so -x c -
+	echo 'int f(void); int _start(void){return f();}' | $(CC) -o $@ -Wl,--no-as-needed -Wl,--disable-new-dtags '-Wl,-rpath,$$ORIGIN' -Wno-implicit-function-declaration -nostdlib liba.so -x c -
 
 exe_runpath: liba.so
-	echo 'int _start(){return f();}' | $(CC) -o $@ -Wl,--no-as-needed -Wl,--enable-new-dtags '-Wl,-rpath,$$ORIGIN' -Wno-implicit-function-declaration -nostdlib liba.so -x c -
+	echo 'int f(void); int _start(void){return f();}' | $(CC) -o $@ -Wl,--no-as-needed -Wl,--enable-new-dtags '-Wl,-rpath,$$ORIGIN' -Wno-implicit-function-declaration -nostdlib liba.so -x c -
 
 check: exe_rpath exe_runpath
 	../../libtree exe_rpath
--- a/tests/02_rpath_of_parents_parent/Makefile
+++ b/tests/02_rpath_of_parents_parent/Makefile
@@ -8,13 +8,13 @@ LD_LIBRARY_PATH=
 all: check
 
 libb.so: 
-	echo 'int g(){return 1;}' | $(CC) -shared -Wl,-soname,$@ -o $@ -nostdlib -x c -
+	echo 'int g(void){return 1;}' | $(CC) -shared -Wl,-soname,$@ -o $@ -nostdlib -x c -
 
 liba.so: libb.so
-	echo 'int f(){return g();}' | $(CC) -shared -Wl,--no-as-needed -Wl,-soname,$@ -o $@ -Wno-implicit-function-declaration libb.so -nostdlib -x c -
+	echo 'int g(void); int f(void){return g();}' | $(CC) -shared -Wl,--no-as-needed -Wl,-soname,$@ -o $@ -Wno-implicit-function-declaration libb.so -nostdlib -x c -
 
 exe: liba.so
-	echo 'int _start(){return f();}' | $(CC) -o $@ -Wl,--no-as-needed -Wl,--disable-new-dtags '-Wl,-rpath,$$ORIGIN' '-Wl,-rpath-link,$(CURDIR)' -Wno-implicit-function-declaration -nostdlib -L. -la -x c -
+	echo 'int f(void); int _start(){return f();}' | $(CC) -o $@ -Wl,--no-as-needed -Wl,--disable-new-dtags '-Wl,-rpath,$$ORIGIN' '-Wl,-rpath-link,$(CURDIR)' -Wno-implicit-function-declaration -nostdlib -L. -la -x c -
 
 check: exe liba.so
 	! ../../libtree liba.so # should not find libb.so
--- a/tests/04_rpath_over_env_over_runpath/Makefile
+++ b/tests/04_rpath_over_env_over_runpath/Makefile
@@ -13,19 +13,19 @@ dir:
 	mkdir $@
 
 dir/liba.so: dir
-	echo 'int a(){return 42;}' | $(CC) -shared -Wl,-soname,$(@F) -Wl,--no-as-needed -o $@ -nostdlib -x c -
+	echo 'int a(void){return 42;}' | $(CC) -shared -Wl,-soname,$(@F) -Wl,--no-as-needed -o $@ -nostdlib -x c -
 
 dir/libb.so: dir/liba.so
-	echo 'int b(){return a();}' | $(CC) -shared -Wl,-soname,$(@F) -Wl,--no-as-needed -Wl,--disable-new-dtags '-Wl,-rpath,$$ORIGIN' -Wno-implicit-function-declaration -o $@ -nostdlib dir/liba.so -x c -
+	echo 'int a(void); int b(void){return a();}' | $(CC) -shared -Wl,-soname,$(@F) -Wl,--no-as-needed -Wl,--disable-new-dtags '-Wl,-rpath,$$ORIGIN' -Wno-implicit-function-declaration -o $@ -nostdlib dir/liba.so -x c -
 
 libb.so:
 	echo 'int b(){return 10;}' | $(CC) -shared -Wl,-soname,$(@F) -Wl,--no-as-needed -o $@ -Wno-implicit-function-declaration -nostdlib -x c -
 
 exe_rpath: libb.so
-	echo 'int _start(){return b();}' | $(CC) -Wl,--no-as-needed -Wl,--disable-new-dtags "-Wl,-rpath,$(CURDIR)" libb.so -o $@ -Wno-implicit-function-declaration -nostdlib -x c -
+	echo 'int b(void); int _start(void){return b();}' | $(CC) -Wl,--no-as-needed -Wl,--disable-new-dtags "-Wl,-rpath,$(CURDIR)" libb.so -o $@ -Wno-implicit-function-declaration -nostdlib -x c -
 
 exe_runpath: libb.so
-	echo 'int _start(){return b();}' | $(CC) -Wl,--no-as-needed -Wl,--enable-new-dtags "-Wl,-rpath,$(CURDIR)" libb.so -o $@ -Wno-implicit-function-declaration -nostdlib -x c -
+	echo 'int b(void); int _start(void){return b();}' | $(CC) -Wl,--no-as-needed -Wl,--enable-new-dtags "-Wl,-rpath,$(CURDIR)" libb.so -o $@ -Wno-implicit-function-declaration -nostdlib -x c -
 
 check: exe_rpath exe_runpath dir/libb.so
 	../../libtree exe_rpath