make sure dlsym() properly returns NULL with undefined symbols

test/dlopen/Makefile

@@ -4,7 +4,7 @@
 # rules need a little love to work with glibc ...
 export UCLIBC_ONLY := 1
 
-TESTS := dltest dltest2 dlstatic test1 test2 test3
+TESTS := dltest dltest2 dlstatic test1 test2 test3 dlundef
 
 include ../Test.mak
 
@@ -14,6 +14,7 @@ CFLAGS_dltest2   := -DLIBNAME="\"./libtest3.so\""
 LDFLAGS_dlstatic := -ldl
 LDFLAGS_dltest   := -ldl -lpthread
 LDFLAGS_dltest2  := -ldl -lpthread
+LDFLAGS_dlundef  := -ldl
 LDFLAGS_test1    := -ldl
 LDFLAGS_test2    := -ldl
 LDFLAGS_test3    := -ldl ./libtest1.so ./libtest2.so -Wl,-rpath,.
@@ -24,6 +25,7 @@ WRAPPER := env $(DEBUG_LIBS)=all LD_LIBRARY_PATH="$$PWD:.:$(LD_LIBRARY_PATH)"
 dltest: libtest.so
 dltest2: libtest3.so
 dlstatic: libstatic.so
+dlundef: libundef.so
 test1: libtest1.so
 test2: libtest1.so libtest2.so
 test3: libtest1.so libtest2.so

test/dlopen/dlundef.c

@@ -0,0 +1,29 @@
+#include <fcntl.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <dlfcn.h>
+#include <stdint.h>
+
+#define LIBNAME "libundef.so"
+
+int main(int argc, char **argv)
+{
+	void *handle;
+	int (*myundefined)(void);
+
+	handle = dlopen(LIBNAME, RTLD_LAZY);
+	if (!handle) {
+		fprintf(stderr, "Could not open ./%s: %s\n", LIBNAME, dlerror());
+		return EXIT_FAILURE;
+	}
+
+	myundefined = dlsym(handle, "__booga_booga_you_cant_touch_this__");
+	if (myundefined != NULL) {
+		fprintf(stderr, "dlsym() found a symbol that does not exist!\n");
+		return EXIT_FAILURE;
+	}
+
+	dlclose(handle);
+
+	return EXIT_SUCCESS;
+}

test/dlopen/libundef.c

@@ -0,0 +1,15 @@
+#include <stdio.h>
+
+static int global_static = -1;
+
+int static_test(void)
+{
+	static int local_static = -2;
+
+	if (global_static != -1)
+		printf("FAIL: global_static is not -1\n");
+	if (local_static != -2)
+		printf("FAIL: local_static is not -2\n");
+
+	return (global_static == -1 && local_static == -2);
+}