[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/memprof/memprof_rtl.cpp

 #include "memprof_thread.h"
 #include "sanitizer_common/sanitizer_atomic.h"
 #include "sanitizer_common/sanitizer_flags.h"
 #include "sanitizer_common/sanitizer_interface_internal.h"
 #include "sanitizer_common/sanitizer_libc.h"
 #include "sanitizer_common/sanitizer_symbolizer.h"
 
 #include <time.h>
+#include <unistd.h>
 
 uptr __memprof_shadow_memory_dynamic_address; // Global interface symbol.
 
 // Allow the user to specify a profile output file via the binary.
 SANITIZER_WEAK_ATTRIBUTE char __memprof_profile_filename[1];
 
 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) {
+      pause();
     }
   }
   if (common_flags()->print_module_map >= 1)
     DumpProcessMap();
   if (flags()->unmap_shadow_on_exit) {
     if (kHighShadowEnd)
       UnmapOrDie((void *)kLowShadowBeg, kHighShadowEnd - kLowShadowBeg);
   }