[GWP-ASan] Use functions in backtrace test, not line numbers.

[hctim]

Summary

There's no unwinding functionality on Android that allows for line
numbers to be retrieved in-process. As a result, we can't have
this backtrace test run on Android.

Cleanup the test to use optnone functions instead, which is more stable
than line numbers anyway.

[eugenis]

LGTM
noinline should be sufficient (instead of optnone)

[hctim]

In D76807#1942445, @eugenis wrote:

LGTM
noinline should be sufficient (instead of optnone)

" If the function does not have side-effects, there are optimizations other than inlining that causes function calls to be optimized away, although the function call is live"

• https://gcc.gnu.org/onlinedocs/gcc-4.7.2/gcc/Function-Attributes.html

With noinline, the call does actually get optimized out in this case. I'm happier with optnone instead of asm("") in the function body :)

compiler-rt/lib/gwp_asan/tests/backtrace.cpp

 //===-- backtrace.cpp -------------------------------------------*- C++ -*-===//
 //
 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
 // See https://llvm.org/LICENSE.txt for license information.
 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 //
 //===----------------------------------------------------------------------===//
 
 #include <string>
 
 #include "gwp_asan/crash_handler.h"
 #include "gwp_asan/tests/harness.h"
 
-TEST_F(BacktraceGuardedPoolAllocator, DoubleFree) {
-  void *Ptr = GPA.allocate(1);
+// Optnone to ensure that the calls to these functions are not optimized away,
+// as we're looking for them in the backtraces.
+__attribute((optnone)) void *
+AllocateMemory(gwp_asan::GuardedPoolAllocator &GPA) {
+  return GPA.allocate(1);
+}
+__attribute((optnone)) void
+DeallocateMemory(gwp_asan::GuardedPoolAllocator &GPA, void *Ptr) {
   GPA.deallocate(Ptr);
+}
+__attribute((optnone)) void
+DeallocateMemory2(gwp_asan::GuardedPoolAllocator &GPA, void *Ptr) {
+  GPA.deallocate(Ptr);
+}
+__attribute__((optnone)) void TouchMemory(void *Ptr) {
+  *(reinterpret_cast<volatile char *>(Ptr)) = 7;
+}
+
+TEST_F(BacktraceGuardedPoolAllocator, DoubleFree) {
+  void *Ptr = AllocateMemory(GPA);
+  DeallocateMemory(GPA, Ptr);
 
   std::string DeathRegex = "Double Free.*";
-  DeathRegex.append("backtrace\\.cpp:26.*");
+  DeathRegex.append("DeallocateMemory2.*");
 
   DeathRegex.append("was deallocated.*");
-  DeathRegex.append("backtrace\\.cpp:16.*");
+  DeathRegex.append("DeallocateMemory.*");
 
   DeathRegex.append("was allocated.*");
-  DeathRegex.append("backtrace\\.cpp:15.*");
-  ASSERT_DEATH(GPA.deallocate(Ptr), DeathRegex);
+  DeathRegex.append("AllocateMemory.*");
+  ASSERT_DEATH(DeallocateMemory2(GPA, Ptr), DeathRegex);
 }
 
 TEST_F(BacktraceGuardedPoolAllocator, UseAfterFree) {
-  char *Ptr = static_cast<char *>(GPA.allocate(1));
-  GPA.deallocate(Ptr);
+  void *Ptr = AllocateMemory(GPA);
+  DeallocateMemory(GPA, Ptr);
 
   std::string DeathRegex = "Use After Free.*";
-  DeathRegex.append("backtrace\\.cpp:41.*");
+  DeathRegex.append("TouchMemory.*");
 
   DeathRegex.append("was deallocated.*");
-  DeathRegex.append("backtrace\\.cpp:31.*");
+  DeathRegex.append("DeallocateMemory.*");
 
   DeathRegex.append("was allocated.*");
-  DeathRegex.append("backtrace\\.cpp:30.*");
-  ASSERT_DEATH({ *Ptr = 7; }, DeathRegex);
+  DeathRegex.append("AllocateMemory.*");
+  ASSERT_DEATH(TouchMemory(Ptr), DeathRegex);
 }
 
 TEST(Backtrace, Short) {
   gwp_asan::AllocationMetadata Meta;
   Meta.AllocationTrace.RecordBacktrace(
       [](uintptr_t *TraceBuffer, size_t /* Size */) -> size_t {
         TraceBuffer[0] = 123u;
         TraceBuffer[1] = 321u;