[memprof] Fix UB.

[fmayer]

Summary

An infinite loop without any effects is illegal C++ and can be optimized
away by the compiler.

[tejohnson]

This was modeled on AsanDie from compiler-rt/lib/asan/asan_rtl.cpp. Do you want to go ahead and fix them both?

[fmayer]

add asan

[fmayer]

remove include

[fmayer]

In D119575#3315208, @tejohnson wrote:

This was modeled on AsanDie from compiler-rt/lib/asan/asan_rtl.cpp. Do you want to go ahead and fix them both?

Done and changed memprof code to not use any system includes. We try to avoid those in ASAN RT.

compiler-rt/lib/asan/asan_rtl.cpp

 namespace __asan {
 
 uptr AsanMappingProfile[kAsanMappingProfileSize];
 
 static void AsanDie() {
   static atomic_uint32_t num_calls;
   if (atomic_fetch_add(&num_calls, 1, memory_order_relaxed) != 0) {
     // Don't die twice - run a busy loop.
-    while (1) { }
+    while (1) {
+      internal_sched_yield();
+    }
   }
   if (common_flags()->print_module_map >= 1)
     DumpProcessMap();
   if (flags()->sleep_before_dying) {
     Report("Sleeping for %d second(s)\n", flags()->sleep_before_dying);
     SleepForSeconds(flags()->sleep_before_dying);
   }
   if (flags()->unmap_shadow_on_exit) {

compiler-rt/lib/memprof/memprof_rtl.cpp

 
 namespace __memprof {
 
 static void MemprofDie() {
   static atomic_uint32_t num_calls;
   if (atomic_fetch_add(&num_calls, 1, memory_order_relaxed) != 0) {
     // Don't die twice - run a busy loop.
     while (1) {
+      internal_sched_yield();
     }
   }
   if (common_flags()->print_module_map >= 1)
     DumpProcessMap();
   if (flags()->unmap_shadow_on_exit) {
     if (kHighShadowEnd)
       UnmapOrDie((void *)kLowShadowBeg, kHighShadowEnd - kLowShadowBeg);
   }