[sanitizer] Make stack traces from dlclose()'d modules more meaningful.

Previously, they silently omitted PCs belonging to unknown modules. Now we print
(<unknown module>) instead.

llvm-svn: 209522

compiler-rt/lib/sanitizer_common/sanitizer_stacktrace_libcdep.cc

@@ -37,6 +37,14 @@ void StackTrace::PrintStack(const uptr *addr, uptr size) {
     uptr pc = GetPreviousInstructionPc(addr[i]);
     uptr addr_frames_num = Symbolizer::GetOrInit()->SymbolizePC(
         pc, addr_frames.data(), addr_frames.size());
+    if (addr_frames_num == 0) {
+      frame_desc.clear();
+      PrintStackFramePrefix(&frame_desc, frame_num, pc);
+      frame_desc.append(" (<unknown module>)");
+      Printf("%s\n", frame_desc.data());
+      frame_num++;
+      continue;
+    }
     for (uptr j = 0; j < addr_frames_num; j++) {
       AddressInfo &info = addr_frames[j];
       frame_desc.clear();

compiler-rt/test/asan/TestCases/Linux/stack-trace-dlclose.cc

@@ -0,0 +1,40 @@
+// RUN: %clangxx_asan -DSHARED %s -shared -o %T/stack_trace_dlclose.so -fPIC
+// RUN: %clangxx_asan -DSO_DIR=\"%T\" %s -o %t
+// RUN: ASAN_OPTIONS=exitcode=0 %run %t 2>&1 | FileCheck %s
+
+#include <assert.h>
+#include <dlfcn.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include <unistd.h>
+
+#include <sanitizer/common_interface_defs.h>
+
+#ifdef SHARED
+extern "C" {
+void *foo() {
+  return malloc(1);
+}
+}
+#else
+void *handle;
+
+int main(int argc, char **argv) {
+  void *handle = dlopen(SO_DIR "/stack_trace_dlclose.so", RTLD_LAZY);
+  assert(handle);
+  void *(*foo)() = (void *(*)())dlsym(handle, "foo");
+  assert(foo);
+  void *p = foo();
+  assert(p);
+  dlclose(handle);
+
+  free(p);
+  free(p);  // double-free
+
+  return 0;
+}
+#endif
+
+// CHECK: {{    #0 0x.* in malloc}}
+// CHECK: {{    #1 0x.* \(<unknown module>\)}}
+// CHECK: {{    #2 0x.* in main}}