user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/tests/rtld/scope4/libbar.c

@@ -0,0 +1,3 @@
+// Bar needs to have a relocation against foo in order to set DT_NEEDED.
+void foo(void);
+void bar() { foo(); }

user/include/mlibc/tests/rtld/scope4/libbaz.c

@@ -0,0 +1 @@
+void baz() {}

user/include/mlibc/tests/rtld/scope4/libfoo.c

@@ -0,0 +1,3 @@
+// Foo needs to have a relocation against baz in order to set DT_NEEDED.
+void baz(void);
+void foo() { baz(); }

user/include/mlibc/tests/rtld/scope4/meson.build

@@ -0,0 +1,9 @@
+libbaz = shared_library('baz', 'libbaz.c')
+libfoo = shared_library('foo', 'libfoo.c', build_rpath: test_rpath, link_with: libbaz)
+libbar = shared_library('bar', 'libbar.c', build_rpath: test_rpath, link_with: libfoo)
+test_depends = [libfoo, libbar, libbaz]
+
+libbaz_native = shared_library('native-baz', 'libbaz.c', native: true)
+libfoo_native = shared_library('native-foo', 'libfoo.c', build_rpath: test_rpath, link_with: libbaz_native, native: true)
+libbar_native = shared_library('native-bar', 'libbar.c', build_rpath: test_rpath, link_with: libfoo_native, native: true)
+test_native_depends = [libfoo_native, libbar_native, libbaz_native]

user/include/mlibc/tests/rtld/scope4/test.c

@@ -0,0 +1,38 @@
+#include <dlfcn.h>
+#include <stdio.h>
+#include <assert.h>
+
+#ifdef USE_HOST_LIBC
+#define LIBFOO "libnative-foo.so"
+#define LIBBAR "libnative-bar.so"
+#define LIBBAZ "libnative-baz.so"
+#else
+#define LIBFOO "libfoo.so"
+#define LIBBAR "libbar.so"
+#define LIBBAZ "libbaz.so"
+#endif
+
+int main() {
+	// In this test, we have foo -> baz, bar -> foo (where '->' means 'depends on').
+	// We first load foo with RTLD_LOCAL, and then load bar with RTLD_GLOBAL.
+	// This should bring foo and bar into the global scope.
+
+	void *foo = dlopen(LIBFOO, RTLD_LOCAL | RTLD_NOW);
+	assert(foo);
+	assert(dlsym(foo, "foo"));
+	assert(dlsym(foo, "baz"));
+	assert(!dlsym(RTLD_DEFAULT, "foo"));
+	assert(!dlsym(RTLD_DEFAULT, "baz"));
+
+	void *bar = dlopen(LIBBAR, RTLD_GLOBAL | RTLD_NOW);
+	assert(bar);
+	assert(dlsym(bar, "bar"));
+	assert(dlsym(RTLD_DEFAULT, "bar"));
+	assert(dlsym(RTLD_DEFAULT, "foo"));
+	assert(dlsym(RTLD_DEFAULT, "baz"));
+
+	dlclose(foo);
+	dlclose(bar);
+
+	return 0;
+}