[lsan] Test to show lsan dependency on globals

This test from @MaskRay comment on D69428. The patch is looking to
break this behavior. If we go with D69428 I hope we will have some
workaround for this test or include explicit test update into the patch.

Reviewed By: MaskRay

Differential Revision: https://reviews.llvm.org/D100906

Author: vitalybuka

compiler-rt/test/lsan/TestCases/use_globals_unused.cpp

@@ -0,0 +1,39 @@
+// Test that unused globals are included in the root set.
+// RUN: %clangxx_lsan -O2 %s -DTEST_LIB -c -o %t.o
+// RUN: %clangxx_lsan -O2 %s %t.o -o %t
+// RUN: LSAN_BASE="use_stacks=0:use_registers=0"
+// RUN: %env_lsan_opts=$LSAN_BASE:"use_globals=0" not %run %t 2>&1 | FileCheck %s --check-prefixes=LEAK
+// RUN: %env_lsan_opts=$LSAN_BASE:"use_globals=1" %run %t 2>&1 | FileCheck %s --implicit-check-not=leak
+// RUN: %env_lsan_opts="" %run %t 2>&1 | FileCheck %s --implicit-check-not=leak
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+
+#ifdef TEST_LIB
+
+void set(char *a) {
+  strcpy(a, "hello");
+}
+
+#else
+
+static void *g;
+
+void set(char *a);
+void foo(void *a) {
+  // Store from a different function to suppress global localization.
+  g = a;
+}
+
+int main() {
+  char a[10];
+  set(a);
+  char *b = strdup(a);
+  printf("%p %s\n", b, b);
+  g = b;
+}
+
+#endif
+
+// LEAK: LeakSanitizer: detected memory leaks