[hwasan] report failing thread for invalid free.

compiler-rt/lib/hwasan/hwasan_report.cpp

void ReportInvalidFree(StackTrace *stack, uptr tagged_addr) {
   uptr untagged_addr = UntagAddr(tagged_addr);
   tag_t ptr_tag = GetTagFromPointer(tagged_addr);
   tag_t *tag_ptr = reinterpret_cast<tag_t*>(MemToShadow(untagged_addr));
   tag_t mem_tag = *tag_ptr;
   Decorator d;
   Printf("%s", d.Error());
   uptr pc = stack->size ? stack->trace[0] : 0;
   const char *bug_type = "invalid-free";
-  Report("ERROR: %s: %s on address %p at pc %p\n", SanitizerToolName, bug_type,
-         untagged_addr, pc);
+  const Thread *thread = GetCurrentThread();
+  if (thread) {
+    Report("ERROR: %s: %s on address %p at pc %p on thread T%zd\n",
+           SanitizerToolName, bug_type, untagged_addr, pc, thread->unique_id());
+  } else {
+    Report("ERROR: %s: %s on address %p at pc %p on unknown thread\n",
+           SanitizerToolName, bug_type, untagged_addr, pc);
+  }
   Printf("%s", d.Access());
   Printf("tags: %02x/%02x (ptr/mem)\n", ptr_tag, mem_tag);
   Printf("%s", d.Default());
 
   stack->Print();
 
   PrintAddressDescription(tagged_addr, 0, nullptr);
 

compiler-rt/test/hwasan/TestCases/double-free.c

 // RUN: %clang_hwasan %s -o %t && not %run %t 2>&1 | FileCheck %s
 
 // REQUIRES: stable-runtime
 
 #include <stdlib.h>
 #include <stdio.h>
 #include <sanitizer/hwasan_interface.h>
 
 int main() {
   __hwasan_enable_allocator_tagging();
   char * volatile x = (char*)malloc(40);
   free(x);
   free(x);
-// CHECK: ERROR: HWAddressSanitizer: invalid-free on address
+// CHECK: ERROR: HWAddressSanitizer: invalid-free on address {{.*}} at pc {{.*}} on thread T{{[0-9]+}}
 // CHECK: tags: [[PTR_TAG:..]]/[[MEM_TAG:..]] (ptr/mem)
 // CHECK: freed by thread {{.*}} here:
 // CHECK: previously allocated here:
 // CHECK: Memory tags around the buggy address (one tag corresponds to 16 bytes):
 // CHECK: =>{{.*}}[[MEM_TAG]]
   fprintf(stderr, "DONE\n");
   __hwasan_disable_allocator_tagging();
 // CHECK-NOT: DONE
 }